If you ever have a need to process messages serially with RabbitMQ with a cluster of listeners processing the messages, the best way that I have seen is to use a "exclusive consumer" flag on a listener with 1 thread on each listener processing the messages. Exclusive consumer flag ensures that only 1 consumer can read messages from the specific queue, and 1 thread on that consumer ensures that the messages are processed serially. There is a catch however, I will go over it later. Let me demonstrate this behavior with a Spring Boot and Spring Integration based RabbitMQ message consumer. First, this is the configuration for setting up a queue using Spring java configuration, note that since this is a Spring Boot application, it automatically creates a RabbitMQ connection factory when the Spring-amqp library is added to the list of dependencies: @Configuration @Configuration public class RabbitConfig { @Autowired private ConnectionFactory rabbitConnectionFactory; @Bean public Queue sampleQueue() { return new Queue("sample.queue", true, false, false); } } Given this sample queue, a listener which gets the messages from this queue and processes them looks like this, the flow is written using the excellent Spring integration Java DSL library: @Configuration public class RabbitInboundFlow { private static final Logger logger = LoggerFactory.getLogger(RabbitInboundFlow.class); @Autowired private RabbitConfig rabbitConfig; @Autowired private ConnectionFactory connectionFactory; @Bean public SimpleMessageListenerContainer simpleMessageListenerContainer() { SimpleMessageListenerContainer listenerContainer = new SimpleMessageListenerContainer(); listenerContainer.setConnectionFactory(this.connectionFactory); listenerContainer.setQueues(this.rabbitConfig.sampleQueue()); listenerContainer.setConcurrentConsumers(1); listenerContainer.setExclusive(true); return listenerContainer; } @Bean public IntegrationFlow inboundFlow() { return IntegrationFlows.from(Amqp.inboundAdapter(simpleMessageListenerContainer())) .transform(Transformers.objectToString()) .handle((m) -> { logger.info("Processed {}", m.getPayload()); }) .get(); } } The flow is very concisely expressed in the inboundFlow method, a message payload from RabbitMQ is transformed from byte array to String and finally processed by simply logging the message to the logs The important part of the flow is the listener configuration, note the flag which sets the consumer to be an exclusive consumer and within this consumer the number of threads processing is set to 1. Given this even if multiple instances of the application is started up only 1 of the listeners will be able to connect and process messages. Now for the catch, consider a case where the processing of messages takes a while to complete and rolls back during processing of the message. If the instance of the application handling the message were to be stopped in the middle of processing such a message, then the behavior is a different instance will start handling the messages in the queue, when the stopped instance rolls back the message, the rolled back message is then delivered to the new exclusive consumer, thus getting a message out of order. If you are interested in exploring this further, here is a github project to play with this feature: https://github.com/bijukunjummen/test-rabbit-exclusive

Spring Integration provides an extension of the Spring framework to support the well-known Enterprise Integration Patterns. It enables lightweight messaging within Spring-based applications and supports integration with external systems. One of the most important goals of Spring Integration is to provide a simple model for building maintainable and testable enterprise integration solutions. Main Components : Message : It is a generic wrapper for any Java object combined with metadata used by the framework while handling that object. It consists of a payload and header(s). Message payload can be any Java Object and Message header is a String/Object Map covering header name and value. MessageBuilder is used to create messages covering payload and headers as follows : import org.springframework.messaging.Message; import org.springframework.messaging.support.MessageBuilder; Message message = MessageBuilder.withPayload("Message Payload") .setHeader("Message_Header1", "Message_Header1_Value") .setHeader("Message_Header2", "Message_Header2_Value") .build(); Message Channel : A message channel is the component through which messages are moved so it can be thought as a pipe between message producer and consumer. A Producer sends the message to a channel, and a consumer receives the message from the channel. A Message Channel may follow either Point-to-Point or Publish/Subscribe semantics. With a Point-to-Point channel, at most one consumer can receive each message sent to the channel. With Publish/Subscribe channels, multiple subscribers can receive each Message sent to the channel. Spring Integration supports both of these. In this sample project, Direct channel and null-channel are used. Direct channel is the default channel type within Spring Integration and simplest point-to-point channel option. Null Channel is a dummy message channel to be used mainly for testing and debugging. It does not send the message from sender to receiver but its send method always returns true and receive method returns null value. In addition to DirectChannel and NullChannel, Spring Integration provides different Message Channel Implementations such as PublishSubscribeChannel, QueueChannel, PriorityChannel, RendezvousChannel, ExecutorChannel and ScopedChannel. Message Endpoint : A message endpoint isolates application code from the infrastructure. In other words, it is an abstraction layer between the application code and the messaging framework. Main Message Endpoints : Transformer : A Message Transformer is responsible for converting a Message’s content or structure and returning the modified Message. For example : it may be used to transform message payload from one format to another or to modify message header values. Filter : A Message Filter determines whether the message should be passed to the message channel. Router : A Message Router decides what channel(s) should receive the Message next if it is available. Splitter : A Splitter breaks an incoming message into multiple messages and send them to the appropriate channel. Aggregator : An Aggregator combines multiple messages into a single message. Service Activator : A Service Activator is a generic endpoint for connecting a service instance to the messaging system. Channel Adapter : A Channel Adapter is an endpoint that connects a Message Channel to external system. Channel Adapters may be either inbound or outbound. An inbound Channel Adapter endpoint connects a external system to a MessageChannel. An outbound Channel Adapter endpoint connects a MessageChannel to a external system. Messaging Gateway : A gateway is an entry point for the messaging system and hides the messaging API from external system. It is bidirectional by covering request and reply channels. Also Spring Integration provides various Channel Adapters and Messaging Gateways (for AMQP, File, Redis, Gemfire, Http, Jdbc, JPA, JMS, RMI, Stream etc..) to support Message-based communication with external systems. Please visit Spring Integration Reference documentation for the detailed information. The following sample Cargo messaging implementation shows basic message endpoints’ behaviours for understanding easily. Cargo messaging system listens cargo messages from external system by using a CargoGateway Interface. Received cargo messages are processed by using CargoSplitter, CargoFilter, CargoRouter, CargoTransformer MessageEndpoints. After then, processed successful domestic and international cargo messages are sent to CargoServiceActivator. Cargo Messaging System’ s Spring Integration Flow is as follows : Let us take a look sample cargo messaging implementation. Used Technologies : JDK 1.8.0_25 Spring 4.1.2 Spring Integration 4.1.0 Maven 3.2.2 Ubuntu 14.04 Project Hierarchy is as follows : STEP 1 : Dependencies Dependencies are added to Maven pom.xml. 4.1.2.RELEASE 4.1.0.RELEASE org.springframework spring-context ${spring.version} org.springframework.integration spring-integration-core ${spring.integration.version} STEP 2 : Cargo Builder CargoBuilder is created to build Cargo requests. public class Cargo { public enum ShippingType { DOMESTIC, INTERNATIONAL } private final long trackingId; private final String receiverName; private final String deliveryAddress; private final double weight; private final String description; private final ShippingType shippingType; private final int deliveryDayCommitment; private final int region; private Cargo(CargoBuilder cargoBuilder) { this.trackingId = cargoBuilder.trackingId; this.receiverName = cargoBuilder.receiverName; this.deliveryAddress = cargoBuilder.deliveryAddress; this.weight = cargoBuilder.weight; this.description = cargoBuilder.description; this.shippingType = cargoBuilder.shippingType; this.deliveryDayCommitment = cargoBuilder.deliveryDayCommitment; this.region = cargoBuilder.region; } // Getter methods... @Override public String toString() { return "Cargo [trackingId=" + trackingId + ", receiverName=" + receiverName + ", deliveryAddress=" + deliveryAddress + ", weight=" + weight + ", description=" + description + ", shippingType=" + shippingType + ", deliveryDayCommitment=" + deliveryDayCommitment + ", region=" + region + "]"; } public static class CargoBuilder { private final long trackingId; private final String receiverName; private final String deliveryAddress; private final double weight; private final ShippingType shippingType; private int deliveryDayCommitment; private int region; private String description; public CargoBuilder(long trackingId, String receiverName, String deliveryAddress, double weight, ShippingType shippingType) { this.trackingId = trackingId; this.receiverName = receiverName; this.deliveryAddress = deliveryAddress; this.weight = weight; this.shippingType = shippingType; } public CargoBuilder setDeliveryDayCommitment(int deliveryDayCommitment) { this.deliveryDayCommitment = deliveryDayCommitment; return this; } public CargoBuilder setDescription(String description) { this.description = description; return this; } public CargoBuilder setRegion(int region) { this.region = region; return this; } public Cargo build() { Cargo cargo = new Cargo(this); if ((ShippingType.DOMESTIC == cargo.getShippingType()) && (cargo.getRegion() <= 0 || cargo.getRegion() > 4)) { throw new IllegalStateException("Region is invalid! Cargo Tracking Id : " + cargo.getTrackingId()); } return cargo; } } STEP 3 : Cargo Message CargoMessage is the parent class of Domestic and International Cargo Messages. public class CargoMessage { private final Cargo cargo; public CargoMessage(Cargo cargo) { this.cargo = cargo; } public Cargo getCargo() { return cargo; } @Override public String toString() { return cargo.toString(); } } STEP 4 : Domestic Cargo Message DomesticCargoMessage Class models domestic cargo messages. public class DomesticCargoMessage extends CargoMessage { public enum Region { NORTH(1), SOUTH(2), EAST(3), WEST(4); private int value; private Region(int value) { this.value = value; } public static Region fromValue(int value) { return Arrays.stream(Region.values()) .filter(region -> region.value == value) .findFirst() .get(); } } private final Region region; public DomesticCargoMessage(Cargo cargo, Region region) { super(cargo); this.region = region; } public Region getRegion() { return region; } @Override public String toString() { return "DomesticCargoMessage [cargo=" + super.toString() + ", region=" + region + "]"; } } STEP 5 : International Cargo Message InternationalCargoMessage Class models international cargo messages. public class InternationalCargoMessage extends CargoMessage { public enum DeliveryOption { NEXT_FLIGHT, PRIORITY, ECONOMY, STANDART } private final DeliveryOption deliveryOption; public InternationalCargoMessage(Cargo cargo, DeliveryOption deliveryOption) { super(cargo); this.deliveryOption = deliveryOption; } public DeliveryOption getDeliveryOption() { return deliveryOption; } @Override public String toString() { return "InternationalCargoMessage [cargo=" + super.toString() + ", deliveryOption=" + deliveryOption + "]"; } } STEP 6 : Application Configuration AppConfiguration is configuration provider class for Spring Container. It creates Message Channels and registers to Spring BeanFactory. Also @EnableIntegration enables imported spring integration configuration and @IntegrationComponentScan scans Spring Integration specific components. Both of them came with Spring Integration 4.0. import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.integration.annotation.IntegrationComponentScan; import org.springframework.integration.channel.DirectChannel; import org.springframework.integration.config.EnableIntegration; import org.springframework.messaging.MessageChannel; @Configuration @ComponentScan("com.onlinetechvision.integration") @EnableIntegration @IntegrationComponentScan("com.onlinetechvision.integration") public class AppConfiguration { /** * Creates a new cargoGWDefaultRequest Channel and registers to BeanFactory. * * @return direct channel */ @Bean public MessageChannel cargoGWDefaultRequestChannel() { return new DirectChannel(); } /** * Creates a new cargoSplitterOutput Channel and registers to BeanFactory. * * @return direct channel */ @Bean public MessageChannel cargoSplitterOutputChannel() { return new DirectChannel(); } /** * Creates a new cargoFilterOutput Channel and registers to BeanFactory. * * @return direct channel */ @Bean public MessageChannel cargoFilterOutputChannel() { return new DirectChannel(); } /** * Creates a new cargoRouterDomesticOutput Channel and registers to BeanFactory. * * @return direct channel */ @Bean public MessageChannel cargoRouterDomesticOutputChannel() { return new DirectChannel(); } /** * Creates a new cargoRouterInternationalOutput Channel and registers to BeanFactory. * * @return direct channel */ @Bean public MessageChannel cargoRouterInternationalOutputChannel() { return new DirectChannel(); } /** * Creates a new cargoTransformerOutput Channel and registers to BeanFactory. * * @return direct channel */ @Bean public MessageChannel cargoTransformerOutputChannel() { return new DirectChannel(); } } STEP 7 : Messaging Gateway CargoGateway Interface exposes domain-specific method to the application. In other words, it provides an application access to the messaging system. Also @MessagingGateway came with Spring Integration 4.0 and simplifies gateway creation in messaging system. Its default request channel is cargoGWDefaultRequestChannel. import java.util.List; import org.springframework.integration.annotation.Gateway; import org.springframework.integration.annotation.MessagingGateway; import org.springframework.messaging.Message; import com.onlinetechvision.model.Cargo; @MessagingGateway(name = "cargoGateway", defaultRequestChannel = "cargoGWDefaultRequestChannel") public interface ICargoGateway { /** * Processes Cargo Request * * @param message SI Message covering Cargo List payload and Batch Cargo Id header. * @return operation result */ @Gateway void processCargoRequest(Message> message); } STEP 8 : Messaging Splitter CargoSplitter listens cargoGWDefaultRequestChannel channel and breaks incoming Cargo List into Cargo messages. Cargo messages are sent to cargoSplitterOutputChannel. import java.util.List; import org.springframework.integration.annotation.MessageEndpoint; import org.springframework.integration.annotation.Splitter; import org.springframework.messaging.Message; import com.onlinetechvision.model.Cargo; @MessageEndpoint public class CargoSplitter { /** * Splits Cargo List to Cargo message(s) * * @param message SI Message covering Cargo List payload and Batch Cargo Id header. * @return cargo list */ @Splitter(inputChannel = "cargoGWDefaultRequestChannel", outputChannel = "cargoSplitterOutputChannel") public List splitCargoList(Message> message) { return message.getPayload(); } } STEP 9 : Messaging Filter CargoFilter determines whether the message should be passed to the message channel. It listens cargoSplitterOutputChannel channel and filters cargo messages exceeding weight limit. If Cargo message is lower than weight limit, it is sent to cargoFilterOutputChannelchannel. If Cargo message is higher than weight limit, it is sent to cargoFilterDiscardChannelchannel. import org.springframework.integration.annotation.Filter; import org.springframework.integration.annotation.MessageEndpoint; import com.onlinetechvision.model.Cargo; @MessageEndpoint public class CargoFilter { private static final long CARGO_WEIGHT_LIMIT = 1_000; /** * Checks weight of cargo and filters if it exceeds limit. * * @param Cargo message * @return check result */ @Filter(inputChannel="cargoSplitterOutputChannel", outputChannel="cargoFilterOutputChannel", discardChannel="cargoFilterDiscardChannel") public boolean filterIfCargoWeightExceedsLimit(Cargo cargo) { return cargo.getWeight() <= CARGO_WEIGHT_LIMIT; } } STEP 10 : Discarded Cargo Message Listener DiscardedCargoMessageListener listens cargoFilterDiscard Channel and handles Cargo messages discarded by CargoFilter. import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.integration.annotation.MessageEndpoint; import org.springframework.integration.annotation.ServiceActivator; import org.springframework.messaging.handler.annotation.Header; import com.onlinetechvision.model.Cargo; @MessageEndpoint public class DiscardedCargoMessageListener { private final Logger logger = LoggerFactory.getLogger(DiscardedCargoMessageListener.class); /** * Handles discarded domestic and international cargo request(s) and logs. * * @param cargo domestic/international cargo message * @param batchId message header shows cargo batch id */ @ServiceActivator(inputChannel = "cargoFilterDiscardChannel") public void handleDiscardedCargo(Cargo cargo, @Header("CARGO_BATCH_ID") long batchId) { logger.debug("Message in Batch[" + batchId + "] is received with Discarded payload : " + cargo); } } STEP 11 : Messaging Router CargoRouter determines what channel(s) should receive the message next if it is available. It listens cargoFilterOutputChannel channel and returns related channel name in the light of cargo shipping type. In other words, it routes incoming cargo messages to domestic(cargoRouterDomesticOutputChannel) or international(cargoRouterInternationalOutputChannel) cargo channels. Also if shipping type is not set, nullChannel is returned. nullChannel is a dummy message channel to be used mainly for testing and debugging. It does not send the message from sender to receiver but its send method always returns true and receive method returns null value. import org.springframework.integration.annotation.MessageEndpoint; import org.springframework.integration.annotation.Router; import com.onlinetechvision.model.Cargo; import com.onlinetechvision.model.Cargo.ShippingType; @MessageEndpoint public class CargoRouter { /** * Determines cargo request' s channel in the light of shipping type. * * @param Cargo message * @return channel name */ @Router(inputChannel="cargoFilterOutputChannel") public String route(Cargo cargo) { if(cargo.getShippingType() == ShippingType.DOMESTIC) { return "cargoRouterDomesticOutputChannel"; } else if(cargo.getShippingType() == ShippingType.INTERNATIONAL) { return "cargoRouterInternationalOutputChannel"; } return "nullChannel"; } } STEP 12 : Messaging Transformer CargoTransformer listens cargoRouterDomesticOutputChannel &cargoRouterInternationalOutputChannel and transforms incoming Cargo requests to Domestic and International Cargo messages. After then, it sends them tocargoTransformerOutputChannel channel. import org.springframework.integration.annotation.MessageEndpoint; import org.springframework.integration.annotation.Transformer; import com.onlinetechvision.model.Cargo; import com.onlinetechvision.model.DomesticCargoMessage; import com.onlinetechvision.model.DomesticCargoMessage.Region; import com.onlinetechvision.model.InternationalCargoMessage; import com.onlinetechvision.model.InternationalCargoMessage.DeliveryOption; @MessageEndpoint public class CargoTransformer { /** * Transforms Cargo request to Domestic Cargo obj. * * @param cargo * request * @return Domestic Cargo obj */ @Transformer(inputChannel = "cargoRouterDomesticOutputChannel", outputChannel = "cargoTransformerOutputChannel") public DomesticCargoMessage transformDomesticCargo(Cargo cargo) { return new DomesticCargoMessage(cargo, Region.fromValue(cargo.getRegion())); } /** * Transforms Cargo request to International Cargo obj. * * @param cargo * request * @return International Cargo obj */ @Transformer(inputChannel = "cargoRouterInternationalOutputChannel", outputChannel = "cargoTransformerOutputChannel") public InternationalCargoMessage transformInternationalCargo(Cargo cargo) { return new InternationalCargoMessage(cargo, getDeliveryOption(cargo.getDeliveryDayCommitment())); } /** * Get delivery option by delivery day commitment. * * @param deliveryDayCommitment delivery day commitment * @return delivery option */ private DeliveryOption getDeliveryOption(int deliveryDayCommitment) { if (deliveryDayCommitment == 1) { return DeliveryOption.NEXT_FLIGHT; } else if (deliveryDayCommitment == 2) { return DeliveryOption.PRIORITY; } else if (deliveryDayCommitment > 2 && deliveryDayCommitment < 5) { return DeliveryOption.ECONOMY; } else { return DeliveryOption.STANDART; } } } STEP 13 : Messaging Service Activator CargoServiceActivator is a generic endpoint for connecting service instance to the messaging system. It listens cargoTransformerOutputChannel channel and gets processed domestic and international cargo messages and logs. import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.integration.annotation.MessageEndpoint; import org.springframework.integration.annotation.ServiceActivator; import org.springframework.messaging.handler.annotation.Header; import com.onlinetechvision.model.CargoMessage; @MessageEndpoint public class CargoServiceActivator { private final Logger logger = LoggerFactory.getLogger(CargoServiceActivator.class); /** * Gets processed domestic and international cargo request(s) and logs. * * @param cargoMessage domestic/international cargo message * @param batchId message header shows cargo batch id */ @ServiceActivator(inputChannel = "cargoTransformerOutputChannel") public void getCargo(CargoMessage cargoMessage, @Header("CARGO_BATCH_ID") long batchId) { logger.debug("Message in Batch[" + batchId + "] is received with payload : " + cargoMessage); } } STEP 14 : Application Application Class is created to run the application. It initializes application context and sends cargo requests to messaging system. import java.util.Arrays; import java.util.Collections; import java.util.HashMap; import java.util.List; import java.util.Map; import org.springframework.context.ApplicationContext; import org.springframework.context.annotation.AnnotationConfigApplicationContext; import org.springframework.messaging.support.MessageBuilder; import com.onlinetechvision.integration.ICargoGateway; import com.onlinetechvision.model.Cargo; import com.onlinetechvision.model.Cargo.ShippingType; public class Application { public static void main(String[] args) { ApplicationContext ctx = new AnnotationConfigApplicationContext(AppConfiguration.class); ICargoGateway orderGateway = ctx.getBean(ICargoGateway.class); getCargoBatchMap().forEach( (batchId, cargoList) -> orderGateway.processCargoRequest(MessageBuilder .withPayload(cargoList) .setHeader("CARGO_BATCH_ID", batchId) .build())); } /** * Creates a sample cargo batch map covering multiple batches and returns. * * @return cargo batch map */ private static Map> getCargoBatchMap() { Map> cargoBatchMap = new HashMap<>(); cargoBatchMap.put(1, Arrays.asList( new Cargo.CargoBuilder(1, "Receiver_Name1", "Address1", 0.5, ShippingType.DOMESTIC) .setRegion(1).setDescription("Radio").build(), //Second cargo is filtered due to weight limit new Cargo.CargoBuilder(2, "Receiver_Name2", "Address2", 2_000, ShippingType.INTERNATIONAL) .setDeliveryDayCommitment(3).setDescription("Furniture").build(), new Cargo.CargoBuilder(3, "Receiver_Name3", "Address3", 5, ShippingType.INTERNATIONAL) .setDeliveryDayCommitment(2).setDescription("TV").build(), //Fourth cargo is not processed due to no shipping type found new Cargo.CargoBuilder(4, "Receiver_Name4", "Address4", 8, null) .setDeliveryDayCommitment(2).setDescription("Chair").build())); cargoBatchMap.put(2, Arrays.asList( //Fifth cargo is filtered due to weight limit new Cargo.CargoBuilder(5, "Receiver_Name5", "Address5", 1_200, ShippingType.DOMESTIC) .setRegion(2).setDescription("Refrigerator").build(), new Cargo.CargoBuilder(6, "Receiver_Name6", "Address6", 20, ShippingType.DOMESTIC) .setRegion(3).setDescription("Table").build(), //Seventh cargo is not processed due to no shipping type found new Cargo.CargoBuilder(7, "Receiver_Name7", "Address7", 5, null) .setDeliveryDayCommitment(1).setDescription("TV").build())); cargoBatchMap.put(3, Arrays.asList( new Cargo.CargoBuilder(8, "Receiver_Name8", "Address8", 200, ShippingType.DOMESTIC) .setRegion(2).setDescription("Washing Machine").build(), new Cargo.CargoBuilder(9, "Receiver_Name9", "Address9", 4.75, ShippingType.INTERNATIONAL) .setDeliveryDayCommitment(1).setDescription("Document").build())); return Collections.unmodifiableMap(cargoBatchMap); } } STEP 15 : Build Project Cargo requests’ operational results are as follows : Cargo 1 : is sent to service activator successfully. Cargo 2 : is filtered due to weight limit. Cargo 3 : is sent to service activator successfully. Cargo 4 : is not processed due to no shipping type. Cargo 5 : is filtered due to weight limit. Cargo 6 : is sent to service activator successfully. Cargo 7 : is not processed due to no shipping type. Cargo 8 : is sent to service activator successfully. Cargo 9 : is sent to service activator successfully. After the project is built and run, the following console output logs will be seen : 2014-12-09 23:43:51 [main] DEBUG c.o.i.CargoServiceActivator - Message in Batch[1] is received with payload : DomesticCargoMessage [cargo=Cargo [trackingId=1, receiverName=Receiver_Name1, deliveryAddress=Address1, weight=0.5, description=Radio, shippingType=DOMESTIC, deliveryDayCommitment=0, region=1], region=NORTH] 2014-12-09 23:43:51 [main] DEBUG c.o.i.DiscardedCargoMessageListener - Message in Batch[1] is received with Discarded payload : Cargo [trackingId=2, receiverName=Receiver_Name2, deliveryAddress=Address2, weight=2000.0, description=Furniture, shippingType=INTERNATIONAL, deliveryDayCommitment=3, region=0] 2014-12-09 23:43:51 [main] DEBUG c.o.i.CargoServiceActivator - Message in Batch[1] is received with payload : InternationalCargoMessage [cargo=Cargo [trackingId=3, receiverName=Receiver_Name3, deliveryAddress=Address3, weight=5.0, description=TV, shippingType=INTERNATIONAL, deliveryDayCommitment=2, region=0], deliveryOption=PRIORITY] 2014-12-09 23:43:51 [main] DEBUG c.o.i.DiscardedCargoMessageListener - Message in Batch[2] is received with Discarded payload : Cargo [trackingId=5, receiverName=Receiver_Name5, deliveryAddress=Address5, weight=1200.0, description=Refrigerator, shippingType=DOMESTIC, deliveryDayCommitment=0, region=2] 2014-12-09 23:43:51 [main] DEBUG c.o.i.CargoServiceActivator - Message in Batch[2] is received with payload : DomesticCargoMessage [cargo=Cargo [trackingId=6, receiverName=Receiver_Name6, deliveryAddress=Address6, weight=20.0, description=Table, shippingType=DOMESTIC, deliveryDayCommitment=0, region=3], region=EAST] 2014-12-09 23:43:51 [main] DEBUG c.o.i.CargoServiceActivator - Message in Batch[3] is received with payload : DomesticCargoMessage [cargo=Cargo [trackingId=8, receiverName=Receiver_Name8, deliveryAddress=Address8, weight=200.0, description=Washing Machine, shippingType=DOMESTIC, deliveryDayCommitment=0, region=2], region=SOUTH] 2014-12-09 23:43:51 [main] DEBUG c.o.i.CargoServiceActivator - Message in Batch[3] is received with payload : InternationalCargoMessage [cargo=Cargo [trackingId=9, receiverName=Receiver_Name9, deliveryAddress=Address9, weight=4.75, description=Document, shippingType=INTERNATIONAL, deliveryDayCommitment=1, region=0], deliveryOption=NEXT_FLIGHT] Source Code Source Code is available on Github References Enterprise Integration Patterns Spring Integration Reference Manual Spring Integration 4.1.0.RELEASE API Pro Spring Integration Spring Integration 3.0.2 and 4.0 Milestone 4 Released

Internationalization refers to automatically showing localized text in your pages for users visiting your site from different regions in the world or localizing the site content based on the language preference chosen by the user. These days most of the web applications are designed to provide rich user experience. With this, the use of JavaScript based UI components has increased many folds. We often need to support internationalization on these JavaScript based Rich Internet Applications (RIA). While looking for JavaScript based internationalization solution I came across a very good jQuery plugin jquery.i18n.properties.js. This plugin uses .properties files to localize the content into different languages. In this tutorial I will show you how we can use this plugin. Getting jquery.i18n.properties.js First of all we need to download the plugin. This is quite lightweight plugin. The file size is around 17.4 KB, but this can be minified and size will reduce to around 4.3 KB. The plugin can be downloaded from https://github.com/jquery-i18n-properties/jquery-i18n-properties. A minified version of the same is available at http://code.google.com/p/jquery-i18n-properties/downloads/list Internationalization Demo The first step as with all JavaScript libraries is to include the JavaScript into HTML. Jquery.i18n.properties.js is a jQuery plugin; hence we need to include jQuery also into HTML before jquery.i18n.properties.js like shown below: Sample HTML Code Before discussing on how to use jquery.i18n.properties.js, let us first create a sample HTML that we will use later. The sample HTML below has a dropdown which allows the user to choose a language. The sample HTML displays two messages which would be localized based on the language chosen from the dropdown. Internationalization using jQuery.i18n.properties Language: Browser Defaultende_DEes_ESfr Welcome to the Demo Site! Your Selected Language is: Default Define .properties files The jquery.i18n.properties.js plugin consumes .properties files for doing text translations. We will use the following .properties files in this demo. Messages.properties msg_welcome = Welcome to the Demo Site! msg_selLang = Your Selected Language is: {0} Messages_es_ES.properties msg_welcome = Bienvenido al sitio de demostración! msg_selLang = El idioma seleccionado es: {0} Loading localized strings from .properties Now we have everything ready to use the plugin, let us see how we can use this plugin to load the translated strings from properties files. The below code sample is used to load the resource bundle properties file using jquery.i18n.properties.js $.i18n.properties({ name: 'Messages', path: 'bundle/', mode: 'both', language: lang, callback: function() { $("#msg_welcome").text($.i18n.prop('msg_welcome')); $("#msg_selLang").text($.i18n.prop('msg_selLang', lang)); } }); The below table provides details about the various options available for $.i18n.properties() (source: http://codingwithcoffee.com/?p=272) Option Description Notes name Name (or names) of files representing resource bundles (eg, ‘Messages’ or ['Msg1','Msg2']) Required String or String[] language ISO-639 Language code and, optionally, ISO-3166 country code (eg, ‘en’, ‘en_US’, ‘pt_PT’). If not specified, language reported by the browser will be used instead. Optional String path Path to directory that contains ‘.properties‘files to load. Optional String mode Option to have resource bundle keys available as JavaScript variables/functions OR as a map. Possible options: ‘vars’ (default), ‘map’ or ‘both’. Optional String callback Callback function to be called upon script execution completion Optional function() Here mode is set to ‘both’ hence the messages can be fetched using map approach as well as JavaScript variables/functions. In the above code sample we used map to retrieve the translated text. The same can be achieved using JavaScript variables/functions as shown below: $("#msg_welcome").text(msg_welcome); $("#msg_selLang").text(msg_selLang(lang)); String parameterization Jquery.i18n.properties.js also supports parameterization of messages. This we have already used in the sample above for the second message. $("#msg_selLang").text($.i18n.prop('msg_selLang', lang)); In the properties file the message is defined as msg_selLang = Your Selected Language is: {0} Here {0} is replaced by the argument ‘lang’ value. As in java resource bundles, we can use multiple {} to define custom messages with multiple parameters. The final output The following screen shots show the output of this demo. The below screen shot is of the default page When the language in drop down is changed to es_ES the text from Message_es_ES.properties is read and displayed as shown below: Advantages of jquery.i18n.properties.js The main advantage of this plugin is that it uses .properties files for internationalization. This is helpful as same properties files could be shared with other parts of the program. The support of parameterization of strings is also beneficial as this enables one to have complex multilingual strings. Has option to use map as well as JavaScript variables/functions for retrieving translated strings. The plugin is very lightweight and can be easily used with any HTML as it is jQuery based.

In my previous articles I compared 4 frameworks commonly used in communicating with MongoDB from the JVM and found out that in that use-case, Spring Data for MongoDB was the easiest solution. However I did make the remark that it doesn’t use the GeoJSON format to store geolocation coordinates and geometries. I tried to add GeoJSON support before, but couldn’t get the conversion to work propertly. But after some extensive searching I found out that the reason for it not working was my use of Spring Boot: its autoconfiguration for MongoDB does not support custom conversion out of the box. Luckily, the solution was simple: provide an extra configuration that extends from AbstractMongoConfiguration and import that in the Boot application. In that configuration you can override the customConversions() and add your converters. When you compare the geo classes in Spring Data and GeoJSON, I noticed that only a subset of GeoJSON geometries can be mapped on Spring Data geo classes: Point and Polygon. Spring Boot does not support LineString, MultiLineString, MultiPolygon or MultiPoint. However, in your mapped domain classes, you won’t use these normally. Creating a converter that adheres to the GeoJSON format is quite straightforward. import com.mongodb.BasicDBObject import com.mongodb.DBObject import org.springframework.core.convert.converter.Converter import org.springframework.data.convert.ReadingConverter import org.springframework.data.convert.WritingConverter import org.springframework.data.geo.Point import org.springframework.data.geo.Polygon final class GeoJsonConverters { static List> getConvertersToRegister() { return [ GeoJsonDBObjectToPointConverter.INSTANCE, GeoJsonDBObjectToPolygonConverter.INSTANCE, GeoJsonPointToDBObjectConverter.INSTANCE, GeoJsonPolygonToDBObjectConverter.INSTANCE ] } @WritingConverter static enum GeoJsonPointToDBObjectConverter implements Converter { INSTANCE; @Override DBObject convert(Point source) { return new BasicDBObject([type: 'Point', coordinates: [source.x, source.y]]) } } @ReadingConverter static enum GeoJsonDBObjectToPointConverter implements Converter { INSTANCE; @Override Point convert(DBObject source) { def coordinates = source.coordinates as double[] return new Point(coordinates[0], coordinates[1]) } } @WritingConverter static enum GeoJsonPolygonToDBObjectConverter implements Converter { INSTANCE; @Override DBObject convert(Polygon source) { def coordinates = source.points.collect { [it.x, it.y] } return new BasicDBObject([type: 'Polygon', coordinates: coordinates]) } } @ReadingConverter static enum GeoJsonDBObjectToPolygonConverter implements Converter { INSTANCE; @Override Polygon convert(DBObject source) { def coordinates = source.coordinates as double[] return new Point(coordinates[0], coordinates[1]) } } } To add those converters to the Spring context, you’ll have to override some methods in your MongoDB spring configuration class. import com.mongodb.Mongo import org.springframework.beans.factory.annotation.* import org.springframework.boot.SpringApplication import org.springframework.boot.autoconfigure.EnableAutoConfiguration import org.springframework.context.annotation.* import org.springframework.data.mongodb.config.AbstractMongoConfiguration import org.springframework.data.mongodb.core.convert.* @EnableAutoConfiguration @ComponentScan @Configuration @Import([MongoComparisonMongoConfiguration]) class MongoComparison { static void main(String[] args) { SpringApplication.run(MongoComparison, args); } } @Configuration class MongoComparisonMongoConfiguration extends AbstractMongoConfiguration { @Autowired Mongo mongo; @Value("\${spring.data.mongodb.database}") String databaseName; @Override protected String getDatabaseName() { return databaseName } @Override Mongo mongo() throws Exception { return mongo } @Override CustomConversions customConversions() { def customConverters = [] customConverters << GeoJsonConverters.convertersToRegister return new CustomConversions(customConverters.flatten()) } } As Spring Boot already provides the configuration of the Mongo instance and the name of the database, we can reuse these in the MongoDB configuration class. The custom conversions take preference over the existing ones for Point and Polygon. I’ll be writing a library this weekend to add support for all GeoJSON geometries in Spring Data for MongoDB. However, I already noticed it’ll be very hard to provide support for those in generated query methods in repositories, but with annotated queries being possible, I don’t think this will be a big issue but we’ll see.

Originally written by Sébastien Deluze on the SpringSource blog Spring Jackson support has been improved lately to be more flexible and powerful. This blog post gives you an update about the most useful Jackson related features available in Spring Framework 4.x and Spring Boot. All the code samples are coming from this spring-jackson-demo sample application, feel free to have a look at the code. JSON Views It can sometimes be useful to filter contextually objects serialized to the HTTP response body. In order to provide such capabilities, Spring MVC now has builtin support for Jackson’s Serialization Views. The following example illustrates how to use @JsonView to filter fields depending on the context of serialization - e.g. getting a "summary" view when dealing with collections, and getting a full representation when dealing with a single resource: public class View { interface Summary {} } public class User { @JsonView(View.Summary.class) private Long id; @JsonView(View.Summary.class) private String firstname; @JsonView(View.Summary.class) private String lastname; private String email; private String address; private String postalCode; private String city; private String country; } public class Message { @JsonView(View.Summary.class) private Long id; @JsonView(View.Summary.class) private LocalDate created; @JsonView(View.Summary.class) private String title; @JsonView(View.Summary.class) private User author; private List recipients; private String body; } Thanks to Spring MVC @JsonView support, it is possible to choose, on a per handler method basis, which field should be serialized: @RestController public class MessageController { @Autowired private MessageService messageService; @JsonView(View.Summary.class) @RequestMapping("/") public List getAllMessages() { return messageService.getAll(); } @RequestMapping("/{id}") public Message getMessage(@PathVariable Long id) { return messageService.get(id); } } In this example, if all messages are retrieved, only the most important fields are serialized thanks to the getAllMessages() method annotated with@JsonView(View.Summary.class): [ { "id" : 1, "created" : "2014-11-14", "title" : "Info", "author" : { "id" : 1, "firstname" : "Brian", "lastname" : "Clozel" } }, { "id" : 2, "created" : "2014-11-14", "title" : "Warning", "author" : { "id" : 2, "firstname" : "Stéphane", "lastname" : "Nicoll" } }, { "id" : 3, "created" : "2014-11-14", "title" : "Alert", "author" : { "id" : 3, "firstname" : "Rossen", "lastname" : "Stoyanchev" } } ] In Spring MVC default configuration, MapperFeature.DEFAULT_VIEW_INCLUSION is set tofalse. That means that when enabling a JSON View, non annotated fields or properties likebody or recipients are not serialized. When a specific Message is retrieved using the getMessage() handler method (no JSON View specified), all fields are serialized as expected: { "id" : 1, "created" : "2014-11-14", "title" : "Info", "body" : "This is an information message", "author" : { "id" : 1, "firstname" : "Brian", "lastname" : "Clozel", "email" : "[email protected]", "address" : "1 Jaures street", "postalCode" : "69003", "city" : "Lyon", "country" : "France" }, "recipients" : [ { "id" : 2, "firstname" : "Stéphane", "lastname" : "Nicoll", "email" : "[email protected]", "address" : "42 Obama street", "postalCode" : "1000", "city" : "Brussel", "country" : "Belgium" }, { "id" : 3, "firstname" : "Rossen", "lastname" : "Stoyanchev", "email" : "[email protected]", "address" : "3 Warren street", "postalCode" : "10011", "city" : "New York", "country" : "USA" } ] } Only one class or interface can be specified with the @JsonView annotation, but you can use inheritance to represent JSON View hierarchies (if a field is part of a JSON View, it will be also part of parent view). For example, this handler method will serialize fields annotated with@JsonView(View.Summary.class) and @JsonView(View.SummaryWithRecipients.class): public class View { interface Summary {} interface SummaryWithRecipients extends Summary {} } public class Message { @JsonView(View.Summary.class) private Long id; @JsonView(View.Summary.class) private LocalDate created; @JsonView(View.Summary.class) private String title; @JsonView(View.Summary.class) private User author; @JsonView(View.SummaryWithRecipients.class) private List recipients; private String body; } @RestController public class MessageController { @Autowired private MessageService messageService; @JsonView(View.SummaryWithRecipients.class) @RequestMapping("/with-recipients") public List getAllMessagesWithRecipients() { return messageService.getAll(); } } JSON Views could also be specified when using RestTemplate HTTP client orMappingJackson2JsonView by wrapping the value to serialize in a MappingJacksonValue as shown in this code sample. JSONP As described in the reference documentation, you can enable JSONP for @ResponseBody andResponseEntity methods by declaring an @ControllerAdvice bean that extendsAbstractJsonpResponseBodyAdvice as shown below: @ControllerAdvice public class JsonpAdvice extends AbstractJsonpResponseBodyAdvice { public JsonpAdvice() { super("callback"); } } With such @ControllerAdvice bean registered, it will be possible to request the JSON webservice from another domain using a In this example, the received payload would be: parseResponse({ "id" : 1, "created" : "2014-11-14", ... }); JSONP is also supported and automatically enabled when using MappingJackson2JsonViewwith a request that has a query parameter named jsonp or callback. The JSONP query parameter name(s) could be customized through the jsonpParameterNames property. XML support Since 2.0 release, Jackson provides first class support for some other data formats than JSON. Spring Framework and Spring Boot provide builtin support for Jackson based XML serialization/deserialization. As soon as you include the jackson-dataformat-xml dependency to your project, it is automatically used instead of JAXB2. Using Jackson XML extension has several advantages over JAXB2: Both Jackson and JAXB annotations are recognized JSON View are supported, allowing you to build easily REST Webservices with the same filtered output for both XML and JSON data formats No need to annotate your class with @XmlRootElement, each class serializable in JSON will serializable in XML You usually also want to make sure that the XML library in use is Woodstox since: It is faster than Stax implementation provided with the JDK It avoids some known issues like adding unnecessary namespace prefixes Some features like pretty print don't work without it In order to use it, simply add the latest woodstox-core-asl dependency available to your project. Customizing the Jackson ObjectMapper Prior to Spring Framework 4.1.1, Jackson HttpMessageConverters were usingObjectMapper default configuration. In order to provide a better and easily customizable default configuration, a new Jackson2ObjectMapperBuilder has been introduced. It is the JavaConfig equivalent of the well known Jackson2ObjectMapperFactoryBean used in XML configuration. Jackson2ObjectMapperBuilder provides a nice API to customize various Jackson settings while retaining Spring Framework provided default ones. It also allows to createObjectMapper and XmlMapper instances based on the same configuration. Both Jackson2ObjectMapperBuilder and Jackson2ObjectMapperFactoryBean define a better Jackson default configuration. For example, theDeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES property set to false, in order to allow deserialization of JSON objects with unmapped properties. Jackson support for Java 8 Date & Time API data types is automatically registered when Java 8 is used and jackson-datatype-jsr310 is on the classpath. Joda-Time support is registered as well when jackson-datatype-joda is part of your project dependencies. These classes also allow you to register easily Jackson mixins, modules, serializers or even property naming strategy like PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES if you want to have your userName java property translated to user_name in JSON. With Spring Boot As described in the Spring Boot reference documentation, there are various ways tocustomize the Jackson ObjectMapper. You can for example enable/disable Jackson features easily by adding properties likespring.jackson.serialization.indent_output=true to application.properties. As an alternative, in the upcoming 1.2 release Spring Boot also allows to customize the Jackson configuration (JSON and XML) used by Spring MVC HttpMessageConverters by declaring a Jackson2ObjectMapperBuilder @Bean: @Bean public Jackson2ObjectMapperBuilder jacksonBuilder() { Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder(); builder.indentOutput(true).dateFormat(new SimpleDateFormat("yyyy-MM-dd")); return builder; } This is useful if you want to use advanced Jackson configuration not exposed through regular configuration keys. Without Spring Boot In a plain Spring Framework application, you can also use Jackson2ObjectMapperBuilder to customize the XML and JSON HttpMessageConverters as shown bellow: @Configuration @EnableWebMvc public class WebConfiguration extends WebMvcConfigurerAdapter { @Override public void configureMessageConverters(List> converters) { Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder(); builder.indentOutput(true).dateFormat(new SimpleDateFormat("yyyy-MM-dd")); converters.add(new MappingJackson2HttpMessageConverter(builder.build())); converters.add(new MappingJackson2XmlHttpMessageConverter(builder.createXmlMapper(true).build())); } } More to come With the upcoming Spring Framework 4.1.3 release, thanks to the addition of a Spring context aware HandlerInstantiator (see SPR-10768 for more details), you will be able to autowire Jackson handlers (serializers, deserializers, type and type id resolvers). This will allow you to build, for example, a custom deserializer that will replace a field containing only a reference in the JSON payload by the full Entity retrieved from the database.

Originally written by Artem Bilan on the SpringSource blog. Dear Spring Community! Recently we published the Spring Integration Java DSL: Line by line tutorial, which uses Java 8 Lambdas extensively. We received some feedback that this is good introduction to the DSL, but a similar tutorial is needed for those users, who can't move to the Java 8 or aren't yet familiar with Lambdas, but wish to take advantage So, to help those Spring Integration users who want to moved from XML configuration to Java & Annotation configuration, we provide this line-by-line tutorial to demonstrate that, even without Lambdas, we gain a lot from Spring Integration Java DSL usage. Although, most will agree that the lambda syntax provides for a more succinct definition. We analyse here the same Cafe Demo sample, but using the pre Java 8 variant for configuration. Many options are the same, so we just copy/paste their description here to achieve a complete picture. Since this Spring Integration Java DSL configuration is quite different to the Java 8 lambda style, it will be useful for all users to get a knowlage how we can achieve the same result with a rich variety of options provided by the Spring Integration Java DSL. The source code for our application is placed in a single class, which is a Boot application; significant lines are annotated with a number corresponding to the comments, which follow: @SpringBootApplication // 1 @IntegrationComponentScan // 2 public class Application { public static void main(String[] args) throws Exception { ConfigurableApplicationContext ctx = SpringApplication.run(Application.class, args); // 3 Cafe cafe = ctx.getBean(Cafe.class); // 4 for (int i = 1; i <= 100; i++) { // 5 Order order = new Order(i); order.addItem(DrinkType.LATTE, 2, false); order.addItem(DrinkType.MOCHA, 3, true); cafe.placeOrder(order); } System.out.println("Hit 'Enter' to terminate"); // 6 System.in.read(); ctx.close(); } @MessagingGateway // 7 public interface Cafe { @Gateway(requestChannel = "orders.input") // 8 void placeOrder(Order order); // 9 } private final AtomicInteger hotDrinkCounter = new AtomicInteger(); private final AtomicInteger coldDrinkCounter = new AtomicInteger(); // 10 @Autowired private CafeAggregator cafeAggregator; // 11 @Bean(name = PollerMetadata.DEFAULT_POLLER) public PollerMetadata poller() { // 12 return Pollers.fixedDelay(1000).get(); } @Bean @SuppressWarnings("unchecked") public IntegrationFlow orders() { // 13 return IntegrationFlows.from("orders.input") // 14 .split("payload.items", (Consumer) null) // 15 .channel(MessageChannels.executor(Executors.newCachedThreadPool()))// 16 .route("payload.iced", // 17 new Consumer>() { // 18 @Override public void accept(RouterSpec spec) { spec.channelMapping("true", "iced") .channelMapping("false", "hot"); // 19 } }) .get(); // 20 } @Bean public IntegrationFlow icedFlow() { // 21 return IntegrationFlows.from(MessageChannels.queue("iced", 10)) // 22 .handle(new GenericHandler() { // 23 @Override public Object handle(OrderItem payload, Map headers) { Uninterruptibles.sleepUninterruptibly(1, TimeUnit.SECONDS); System.out.println(Thread.currentThread().getName() + " prepared cold drink #" + coldDrinkCounter.incrementAndGet() + " for order #" + payload.getOrderNumber() + ": " + payload); return payload; // 24 } }) .channel("output") // 25 .get(); } @Bean public IntegrationFlow hotFlow() { // 26 return IntegrationFlows.from(MessageChannels.queue("hot", 10)) .handle(new GenericHandler() { @Override public Object handle(OrderItem payload, Map headers) { Uninterruptibles.sleepUninterruptibly(5, TimeUnit.SECONDS); // 27 System.out.println(Thread.currentThread().getName() + " prepared hot drink #" + hotDrinkCounter.incrementAndGet() + " for order #" + payload.getOrderNumber() + ": " + payload); return payload; } }) .channel("output") .get(); } @Bean public IntegrationFlow resultFlow() { // 28 return IntegrationFlows.from("output") // 29 .transform(new GenericTransformer() { // 30 @Override public Drink transform(OrderItem orderItem) { return new Drink(orderItem.getOrderNumber(), orderItem.getDrinkType(), orderItem.isIced(), orderItem.getShots()); // 31 } }) .aggregate(new Consumer() { // 32 @Override public void accept(AggregatorSpec aggregatorSpec) { aggregatorSpec.processor(cafeAggregator, null); // 33 } }, null) .handle(CharacterStreamWritingMessageHandler.stdout()) // 34 .get(); } @Component public static class CafeAggregator { // 35 @Aggregator // 36 public Delivery output(List drinks) { return new Delivery(drinks); } @CorrelationStrategy // 37 public Integer correlation(Drink drink) { return drink.getOrderNumber(); } } } Examining the code line by line... 1. @SpringBootApplication This new meta-annotation from Spring Boot 1.2. Includes @Configuration and@EnableAutoConfiguration. Since we are in a Spring Integration application and Spring Boot has auto-configuration for it, the @EnableIntegration is automatically applied, to initialize the Spring Integration infrastructure including an environment for the Java DSL -DslIntegrationConfigurationInitializer, which is picked up by theIntegrationConfigurationBeanFactoryPostProcessor from /META-INF/spring.factories. 2. @IntegrationComponentScan The Spring Integration analogue of @ComponentScan to scan components based on interfaces, (the Spring Framework's @ComponentScan only looks at classes). Spring Integration supports the discovery of interfaces annotated with @MessagingGateway (see #7 below). 3. ConfigurableApplicationContext ctx = SpringApplication.run(Application.class, args); The main method of our class is designed to start the Spring Boot application using the configuration from this class and starts an ApplicationContext via Spring Boot. In addition, it delegates command line arguments to the Spring Boot. For example you can specify --debug to see logs for the boot auto-configuration report. 4. Cafe cafe = ctx.getBean(Cafe.class); Since we already have an ApplicationContext we can start to interact with application. AndCafe is that entry point - in EIP terms a gateway. Gateways are simply interfaces and the application does not interact with the Messaging API; it simply deals with the domain (see #7 below). 5. for (int i = 1; i <= 100; i++) { To demonstrate the cafe "work" we intiate 100 orders with two drinks - one hot and one iced. And send the Order to the Cafe gateway. 6. System.out.println("Hit 'Enter' to terminate"); Typically Spring Integration application are asynchronous, hence to avoid early exit from themain Thread we block the main method until some end-user interaction through the command line. Non daemon threads will keep the application open but System.read()provides us with a mechanism to close the application cleanly. 7. @MessagingGateway The annotation to mark a business interface to indicate it is a gateway between the end-application and integration layer. It is an analogue of component from Spring Integration XML configuration. Spring Integration creates a Proxy for this interface and populates it as a bean in the application context. The purpose of this Proxy is to wrap parameters in a Message object and send it to the MessageChannel according to the provided options. 8. @Gateway(requestChannel = "orders.input") The method level annotation to distinct business logic by methods as well as by the target integration flows. In this sample we use a requestChannel reference of orders.input, which is a MessageChannel bean name of our IntegrationFlow input channel (see below #14). 9. void placeOrder(Order order); The interface method is a central point to interact from end-application with the integration layer. This method has a void return type. It means that our integration flow is one-wayand we just send messages to the integration flow, but don't wait for a reply. 10. private AtomicInteger hotDrinkCounter = new AtomicInteger(); private AtomicInteger coldDrinkCounter = new AtomicInteger(); Two counters to gather the information how our cafe works with drinks. 11. @Autowired private CafeAggregator cafeAggregator; The POJO for the Aggregator logic (see #33 and #35 below). Since it is a Spring bean, we can simply inject it even to the current @Configuration and use in any place below, e.g. from the .aggregate() EIP-method. 12. @Bean(name = PollerMetadata.DEFAULT_POLLER) public PollerMetadata poller() { The default poller bean. It is a analogue of component from Spring Integration XML configuration. Required for endpoints where the inputChannelis a PollableChannel. In this case, it is necessary for the two Cafe queues - hot and iced (see below #18). Here we use the Pollers factory from the DSL project and use its method-chain fluent API to build the poller metadata. Note that Pollers can be used directly from an IntegrationFlow definition, if a specific poller (rather than the default poller) is needed for an endpoint. 13. @Bean public IntegrationFlow orders() { The IntegrationFlow bean definition. It is the central component of the Spring Integration Java DSL, although it does not play any role at runtime, just during the bean registration phase. All other code below registers Spring Integration components (MessageChannel,MessageHandler, EventDrivenConsumer, MessageProducer, MessageSource etc.) in theIntegrationFlow object, which is parsed by the IntegrationFlowBeanPostProcessor to process those components and register them as beans in the application context as necessary (some elements, such as channels may already exist). 14. return IntegrationFlows.from("orders.input") The IntegrationFlows is the main factory class to start the IntegrationFlow. It provides a number of overloaded .from() methods to allow starting a flow from aSourcePollingChannelAdapter for a MessageSource implementations, e.g.JdbcPollingChannelAdapter; from a MessageProducer, e.g.WebSocketInboundChannelAdapter; or simply a MessageChannel. All ".from()" options have several convenient variants to configure the appropriate component for the start of theIntegrationFlow. Here we use just a channel name, which is converted to aDirectChannel bean definition during the bean definition phase while parsing theIntegrationFlow. In the Java 8 variant, we used here a Lambda definition - and thisMessageChannel has been implicitly created with the bean name based on theIntegrationFlow bean name. 15. .split("payload.items", (Consumer) null) Since our integration flow accepts messages through the orders.input channel, we are ready to consume and process them. The first EIP-method in our scenario is .split(). We know that the message payload from orders.input channel is an Order domain object, so we can simply use here a Spring (SpEL) Expression to return Collection. So, this performs the split EI pattern, and we send each collection entry as a separate message to the next channel. In the background, the .split() method registers aExpressionEvaluatingSplitter MessageHandler implementation and anEventDrivenConsumer for that MessageHandler, wiring in the orders.input channel as the inputChannel. The second argument for the .split() EIP-method is for an endpointConfigurer to customize options like autoStartup, requiresReply, adviceChain etc. We use herenull to show that we rely on the default options for the endpoint. Many of EIP-methods provide overloaded versions with and without endpointConfigurer. Currently.split(String expression) EIP-method without the endpointConfigurer argument is not available; this will be addressed in a future release. 16. .channel(MessageChannels.executor(Executors.newCachedThreadPool())) The .channel() EIP-method allows the specification of concrete MessageChannels between endpoints, as it is done via output-channel/input-channel attributes pair with Spring Integration XML configuration. By default, endpoints in the DSL integration flow definition are wired with DirectChannels, which get bean names based on theIntegrationFlow bean name and index in the flow chain. In this case we select a specificMessageChannel implementation from the Channels factory class; the selected channel here is an ExecutorChannel, to allow distribution of messages from the splitter to separate Threads, to process them in parallel in the downstream flow. 17. .route("payload.iced", The next EIP-method in our scenario is .route(), to send hot/iced order items to different Cafe kitchens. We again use here a SpEL expression to get the routingKey from the incoming message. In the Java 8 variant, we used a method-reference Lambda expression, but for pre Java 8 style we must use SpEL or an inline interface implementation. Many anonymous classes in a flow can make the flow difficult to read so we prefer SpEL in most cases. 18. new Consumer>() { The second argument of .route() EIP-method is a functional interface Consumer to specify ExpressionEvaluatingRouter options using a RouterSpec Builder. Since we don't have any choice with pre Java 8, we just provide here an inline implementation for this interface. 19. spec.channelMapping("true", "iced") .channelMapping("false", "hot"); With the Consumer>#accept()implementation we can provide desired AbstractMappingMessageRouter options. One of them is channelMappings, when we specify the routing logic by the result of router expresion and the target MessageChannel for the apropriate result. In this case iced andhot are MessageChannel names for IntegrationFlows below. 20. .get(); This finalizes the flow. Any IntegrationFlows.from() method returns anIntegrationFlowBuilder instance and this get() method extracts an IntegrationFlowobject from the IntegrationFlowBuilder configuration. Everything starting from the.from() and up to the method before the .get() is an IntegrationFlow definition. All defined components are stored in the IntegrationFlow and processed by theIntegrationFlowBeanPostProcessor during the bean creation phase. 21. @Bean public IntegrationFlow icedFlow() { This is the second IntegrationFlow bean definition - for iced drinks. Here we demonstrate that several IntegrationFlows can be wired together to create a single complex application. Note: it isn't recommended to inject one IntegrationFlow to another; it might cause unexpected behaviour. Since they provide Integration components for the bean registration and MessageChannels one of them, the best way to wire and inject is viaMessageChannel or @MessagingGateway interfaces. 22. return IntegrationFlows.from(MessageChannels.queue("iced", 10)) The iced IntegrationFlow starts from a QueueChannel that has a capacity of 10messages; it is registered as a bean with the name iced. As you remember we use this name as one of the route mappings (see above #19). In our sample, we use here a restricted QueueChannel to reflect the Cafe kitchen busy state from real life. And here is a place where we need that global poller for the next endpoint which is listening on this channel. 23. .handle(new GenericHandler() { The .handle() EIP-method of the iced flow demonstrates the concrete Cafe kitchen work. Since we can't minimize the code with something like Java 8 Lambda expression, we provide here an inline implementation for the GenericHandler functional interface with the expected payload type as the generic argument. With the Java 8 example, we distribute this.handle() between several subscriber subflows for a PublishSubscribeChannel. However in this case, the logic is all implemented in the one method. 24. Uninterruptibles.sleepUninterruptibly(1, TimeUnit.SECONDS); System.out.println(Thread.currentThread().getName() + " prepared cold drink #" + coldDrinkCounter.incrementAndGet() + " for order #" + payload.getOrderNumber() + ": " + payload); return payload; The business logic implementation for the current .handle() EIP-component. WithUninterruptibles.sleepUninterruptibly(1, TimeUnit.SECONDS); we just block the current Thread for some timeout to demonstrate how quickly the Cafe kitchen prepares a drink. After that we just report to STDOUT that the drink is ready and return the currentOrderItem from the GenericHandler for the next endpoint in our IntegrationFlow. In the background, the DSL framework registers a ServiceActivatingHandler for theMethodInvokingMessageProcessor to invoke the GenericHandler#handle at runtime. In addition, the framework registers a PollingConsumer endpoint for the QueueChannelabove. This endpoint relies on the default poller to poll messages from the queue. Of course, we always can use a specific poller for any concrete endpoint. In that case, we would have to provide a second endpointConfigurer argument to the .handle() EIP-method. 25. .channel("output") Since it is not the end of our Cafe scenario, we send the result of the current flow to theoutput channel using the convenient EIP-method .channel() and the name of theMessageChannel bean (see below #29). This is the logical end of the current iced drink subflow, so we use the .get() method to return the IntegrationFlow. Flows that end with a reply-producing handler that don't have a final .channel() will return the reply to the message replyChannel header. 26. @Bean public IntegrationFlow hotFlow() { The IntegrationFlow definition for hot drinks. It is similar to the previous iced drinks flow, but with specific hot business logic. It starts from the hot QueueChannel which is mapped from the router above. 27. Uninterruptibles.sleepUninterruptibly(5, TimeUnit.SECONDS); The sleepUninterruptibly for hot drinks. Right, we need more time to boil the water! 28. @Bean public IntegrationFlow resultFlow() { One more IntegrationFlow bean definition to prepare the Delivery for the Cafe client based on the Drinks. 29. return IntegrationFlows.from("output") The resultFlow starts from the DirectChannel, which is created during the bean definition phase with this provided name. You should remember that we use the outputchannel name from the Cafe kitchens flows in the last .channel() in those definitions. 30. .transform(new GenericTransformer() { The .transform() EIP-method is for the appropriate pattern implementation and expects some object to convert one payload to another. In our sample we use an inline implementation of the GenericTransformer functional interface to convert OrderItem to Drink and we specify that using generic arguments. In the background, the DSL framework registers aMessageTransformingHandler and an EventDrivenConsumer endpoint with default options to consume messages from the output MessageChannel. 31. public Drink transform(OrderItem orderItem) { return new Drink(orderItem.getOrderNumber(), orderItem.getDrinkType(), orderItem.isIced(), orderItem.getShots()); } The business-specific GenericTransformer#transform() implementation to demonstrate how we benefit from Java Generics to transform one payload to another. Note: Spring Integration uses ConversionService before any method invocation and if you provide some specific Converter implementation, some domain payload can be converted to another automatically, when the framework has an appropriate registered Converter. 32. .aggregate(new Consumer() { The .aggregate() EIP-method provides options to configure anAggregatingMessageHandler and its endpoint, similar to what we can do with the component when using Spring Integration XML configuration. Of course, with the Java DSL we have more power to configure the aggregator in place, without any other extra beans. However we demonstrate here an aggregator configuration with annotations (see below #35). From the Cafe business logic perspective we compose the Delivery for the initial Order, since we .split() the original order to the OrderItems near the beginning. 33. public void accept(AggregatorSpec aggregatorSpec) { aggregatorSpec.processor(cafeAggregator, null); } An inline implementation of the Consumer for the AggregatorSpec. Using theaggregatorSpec Builder we can provide desired options for the aggregator component, which will be registered as an AggregatingMessageHandler bean. Here we just provide theprocessor as a reference to the autowired (see #11 above) CafeAggregator component (see #35 below). The second argument of the .processor() option is methodName. Since we are relying on the aggregator annotation configuration for the POJO, we don't need to provide the method here and the framework will determine the correct POJO methods in the background. 34. .handle(CharacterStreamWritingMessageHandler.stdout()) It is the end of our flow - the Delivery is delivered to the client! We just print here the message payload to STDOUT using out-of-the-boxCharacterStreamWritingMessageHandler from Spring Integration Core. This is a case to show how existing components from Spring Integration Core (and its modules) can be used from the Java DSL. 35. @Component public static class CafeAggregator { The bean to specify the business logic for the aggregator above. This bean is picked up by the @ComponentScan, which is a part of the @SpringBootApplication meta-annotation (see above #1). So, this component becomes a bean and we can automatically wire (@Autowired) it to other components in the application context (see #11 above). 36. @Aggregator public Delivery output(List drinks) { return new Delivery(drinks); } The POJO-specific MessageGroupProcessor to build the output payload based on the payloads from aggregated messages. Since we mark this method with the @Aggregatorannotation, the target AggregatingMessageHandler can extract this method for theMethodInvokingMessageGroupProcessor. 37. @CorrelationStrategy public Integer correlation(Drink drink) { return drink.getOrderNumber(); } The POJO-specific CorrelationStrategy to extract the custom correlationKey from each inbound aggregator message. Since we mark this method with @CorrelationStrategyannotation the target AggregatingMessageHandler can extract this method for theMethodInvokingCorrelationStrategy. There is a similar self-explained@ReleaseStrategy annotation, but we rely in our Cafe sample just on the defaultSequenceSizeReleaseStrategy, which is based on the sequenceDetails message header populated by the splitter from the beginning of our integration flow. Well, we have finished describing the Cafe Demo sample based on the Spring Integration Java DSL when Java Lambda support is not available. Compare it with XML sample and also seeLambda support tutorial to get more information regarding Spring Integration. As you can see, using the DSL without lambdas is a little more verbose because you need to provide boilerplate code for inline anonymous implementations of functional interfaces. However, we believe it is important to support the use of the DSL for users who can't yet move to Java 8. Many of the DSL benefits (fluent API, compile-time validation etc) are available for all users. The use of lambdas continues the Spring Framework tradition of reducing or eliminating boilerplate code, so we encourage users to try Java 8 and lambdas and to encourage their organizations to consider allowing the use of Java 8 for Spring Integration applications. In addition see the Reference Manual for more information. As always, we look forward to your comments and feedback (StackOverflow (spring-integration tag), Spring JIRA, GitHub) and we very much welcome contributions! Thank you for your time and patience to read this!

Spring Data REST is an awesome project that provides mechanisms to expose the resources underlying a Spring Data based repository as REST resources. Exposing a service with a linked resource Consider two simple JPA based entities, Course and Teacher: @Entity @Table(name = "teachers") public class Teacher { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id") private Long id; @Size(min = 2, max = 50) @Column(name = "name") private String name; @Column(name = "department") @Size(min = 2, max = 50) private String department; ... } @Entity @Table(name = "courses") public class Course { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id") private Long id; @Size(min = 1, max = 10) @Column(name = "coursecode") private String courseCode; @Size(min = 1, max = 50) @Column(name = "coursename") private String courseName; @ManyToOne @JoinColumn(name = "teacher_id") private Teacher teacher; .... } essentially the relation looks like this: Now, all it takes to expose these entities as REST resources is adding a @RepositoryRestResource annotation on their JPA based Spring Data repositories this way, first for the "Teacher" resource: import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.rest.core.annotation.RepositoryRestResource; import univ.domain.Teacher; @RepositoryRestResource public interface TeacherRepo extends JpaRepository { } and for exposing the Course resource: @RepositoryRestResource public interface CourseRepo extends JpaRepository { } With this done and assuming a few teachers and a few courses are already in the datastore, a GET on courses would yield a response of the following type: { "_links" : { "self" : { "href" : "http://localhost:8080/api/courses{?page,size,sort}", "templated" : true } }, "_embedded" : { "courses" : [ { "courseCode" : "Course1", "courseName" : "Course Name 1", "version" : 0, "_links" : { "self" : { "href" : "http://localhost:8080/api/courses/1" }, "teacher" : { "href" : "http://localhost:8080/api/courses/1/teacher" } } }, { "courseCode" : "Course2", "courseName" : "Course Name 2", "version" : 0, "_links" : { "self" : { "href" : "http://localhost:8080/api/courses/2" }, "teacher" : { "href" : "http://localhost:8080/api/courses/2/teacher" } } } ] }, "page" : { "size" : 20, "totalElements" : 2, "totalPages" : 1, "number" : 0 } } and a specific course looks like this: { "courseCode" : "Course1", "courseName" : "Course Name 1", "version" : 0, "_links" : { "self" : { "href" : "http://localhost:8080/api/courses/1" }, "teacher" : { "href" : "http://localhost:8080/api/courses/1/teacher" } } } If you are wondering what the "_links", "_embedded" are - Spring Data REST uses Hypertext Application Language(or HAL for short) to represent the links, say the one between a course and a teacher. HAL Based REST service - Using RestTemplate Given this HAL based REST service, the question that I had in my mind was how to write a client to this service. I am sure there are better ways of doing this, but what follows worked for me and I welcome any cleaner ways of writing the client. First, I modified the RestTemplate to register a custom Json converter that understands HAL based links: public RestTemplate getRestTemplateWithHalMessageConverter() { RestTemplate restTemplate = new RestTemplate(); List> existingConverters = restTemplate.getMessageConverters(); List> newConverters = new ArrayList<>(); newConverters.add(getHalMessageConverter()); newConverters.addAll(existingConverters); restTemplate.setMessageConverters(newConverters); return restTemplate; } private HttpMessageConverter getHalMessageConverter() { ObjectMapper objectMapper = new ObjectMapper(); objectMapper.registerModule(new Jackson2HalModule()); MappingJackson2HttpMessageConverter halConverter = new TypeConstrainedMappingJackson2HttpMessageConverter(ResourceSupport.class); halConverter.setSupportedMediaTypes(Arrays.asList(HAL_JSON)); halConverter.setObjectMapper(objectMapper); return halConverter; } The Jackson2HalModule is provided by the Spring HATEOS project and understands HAL representation. Given this shiny new RestTemplate, first let us create a Teacher entity: Teacher teacher1 = new Teacher(); teacher1.setName("Teacher 1"); teacher1.setDepartment("Department 1"); URI teacher1Uri = testRestTemplate.postForLocation("http://localhost:8080/api/teachers", teacher1); Note that when the entity is created, the response is a http status code of 201 with the Location header pointing to the uri of the newly created resource, Spring RestTemplate provides a neat way of posting and getting hold of this Location header through an API. So now we have a teacher1Uri representing the newly created teacher. Given this teacher URI, let us now retrieve the teacher, the raw json for the teacher resource looks like the following: { "name" : "Teacher 1", "department" : "Department 1", "version" : 0, "_links" : { "self" : { "href" : "http://localhost:8080/api/teachers/1" } } } and to retrieve this using RestTemplate: ResponseEntity> teacherResponseEntity = testRestTemplate.exchange("http://localhost:8080/api/teachers/1", HttpMethod.GET, null, new ParameterizedTypeReference>() { }); Resource teacherResource = teacherResponseEntity.getBody(); Link teacherLink = teacherResource.getLink("self"); String teacherUri = teacherLink.getHref(); Teacher teacher = teacherResource.getContent(); Jackson2HalModule is the one which helps unpack the links this cleanly and to get hold of the Teacher entity itself. I have previously explained ParameterizedTypeReference here. Now, to a more tricky part, creating a Course. Creating a course is tricky as it has a relation to the Teacher and representing this relation using HAL is not that straightforward. A raw POST to create the course would look like this: { "courseCode" : "Course1", "courseName" : "Course Name 1", "version" : 0, "teacher" : "http://localhost:8080/api/teachers/1" } Note how the reference to the teacher is a URI, this is how HAL represents an embedded reference specifically for a POST'ed content, so now to get this form through RestTemplate - First to create a Course: Course course1 = new Course(); course1.setCourseCode("Course1"); course1.setCourseName("Course Name 1"); At this point, it will be easier to handle providing the teacher link by dealing with a json tree representation and adding in the teacher link as the teacher uri: ObjectMapper objectMapper = getObjectMapperWithHalModule(); ObjectNode jsonNodeCourse1 = (ObjectNode) objectMapper.valueToTree(course1); jsonNodeCourse1.put("teacher", teacher1Uri.getPath()); and posting this should create the course with the linked teacher: URI course1Uri = testRestTemplate.postForLocation(coursesUri, jsonNodeCourse1); and to retrieve this newly created Course: ResponseEntity> courseResponseEntity = testRestTemplate.exchange(course1Uri, HttpMethod.GET, null, new ParameterizedTypeReference>() { }); Resource courseResource = courseResponseEntity.getBody(); Link teacherLinkThroughCourse = courseResource.getLink("teacher"); This concludes how to use the RestTemplate to create and retrieve a linked resource, alternate ideas are welcome. If you are interested in exploring this further, the entire sample is available at this github repo - and the test is here

When I needed to do prototyping, proof of concept or play with some new technology in free time, starting new project was always a little annoying barrier with Maven. Have to say that setting up Maven project is not hard and you can use Maven Archetypes. But Archetypes are often out of date. Who wants to play with old technologies? So I always end up wiring in dependencies I wanted to play with. Not very productive spent time. But than Spring Boot came to my way. I fell in love. In last few months I created at least 50 small playground projects, prototypes with Spring Boot. Also incorporated it at work. It’s just perfect for prototyping, learning, microservices, web, batch, enterprise, message flow or command line applications. You have to be dinosaur or be blind not to evaluate Spring Boot for your next Spring project. And when you finish evaluate it, you will go for it. I promise. I feel a need to highlight how easy is Black Box Testing of Spring Boot microservice. Black Box Testing refers to testing without any poking with application artifact. Such testing can be called also integration testing. You can also perform performance or stress testing way I am going to demonstrate. Spring Boot Microservice is usually web application with embedded Tomcat. So it is executed as JAR from command line. There is possibility to convert Spring Boot project into WAR artifact, that can be hosted on shared Servlet container. But we don’t want that now. It’s better when microservice has its own little embedded container. I used existing Spring’s REST service guide as testing target. Focus is mostly on testing project, so it is handy to use this “Hello World” REST application as example. I expect these two common tools are set up and installed on your machine: Maven 3 Git So we’ll need to download source code and install JAR artifact into our local repository. I am going to use command line to download and install the microservice. Let’s go to some directory where we download source code. Use these commands: git clone [email protected]:spring-guides/gs-rest-service.git cd gs-rest-service/complete mvn clean install If everything went OK, Spring Boot microservice JAR artifact is now installed in our local Maven repository. In serious Java development, it would be rather installed into shared repository (e.g. Artifactory, Nexus,… ). When our microservice is installed, we can focus on testing project. It is also Maven and Spring Boot based. Black box testing will be achieved by downloading the artifact from Maven repository (doesn’t matter if it is local or remote). Maven-dependency-plugin can help us this way: org.apache.maven.plugins maven-dependency-plugin copy-dependencies compile copy-dependencies gs-rest-service true It downloads microservice artifact into target/dependency directory by default. As you can see, it’s hooked to compile phase of Maven lifecycle, so that downloaded artifact is available during test phase. Artifact version is stripped from version information. We use latest version. It makes usage of JAR artifact easier during testing. Readers skilled with Maven may notice missing plugin version. Spring Boot driven project is inherited from parent Maven project called spring-boot-starter-parent. It contains versions of main Maven plugins. This is one of the Spring Boot’s opinionated aspects. I like it, because it provides stable dependencies matrix. You can change the version if you need. When we have artifact in our file system, we can start testing. We need to be able to execute JAR file from command line. I used standard JavaProcessBuilder this way: public class ProcessExecutor { public Process execute(String jarName) throws IOException { Process p = null; ProcessBuilder pb = new ProcessBuilder("java", "-jar", jarName); pb.directory(new File("target/dependency")); File log = new File("log"); pb.redirectErrorStream(true); pb.redirectOutput(Redirect.appendTo(log)); p = pb.start(); return p; } } This class executes given process JAR based on given file name. Location is hard-coded to target/dependency directory, where maven-dependency-plugin located our artifact. Standard and error outputs are redirected to file. Next class needed for testing is DTO (Data transfer object). It is simple POJO that will be used for deserialization from JSON. I use Lombok project to reduce boilerplate code needed for getters, setters, hashCode and equals. @Data @AllArgsConstructor @NoArgsConstructor public class Greeting { private long id; private String content; } Test itself looks like this: public class BlackBoxTest { private static final String RESOURCE_URL = "http://localhost:8080/greeting"; @Test public void contextLoads() throws InterruptedException, IOException { Process process = null; Greeting actualGreeting = null; try { process = new ProcessExecutor().execute("gs-rest-service.jar"); RestTemplate restTemplate = new RestTemplate(); waitForStart(restTemplate); actualGreeting = restTemplate.getForObject(RESOURCE_URL, Greeting.class); } finally { process.destroyForcibly(); } Assert.assertEquals(new Greeting(2L, "Hello, World!"), actualGreeting); } private void waitForStart(RestTemplate restTemplate) { while (true) { try { Thread.sleep(500); restTemplate.getForObject(RESOURCE_URL, String.class); return; } catch (Throwable throwable) { // ignoring errors } } } } It executes Spring Boot microservice process first and wait unit it starts. To verify if microservice is started, it sends HTTP request to URL where it’s expected. The service is ready for testing after first successful response. Microservice should send simple greeting JSON response for HTTP GET request. Deserialization from JSON into our Greeting DTO is verified at the end of the test. Source code is shared on Github.

I came through interesting problem on Stack Overflow. Brett Ryan had problem that Spring Security configuration was initialized twice. When I was looking into his code I spot the problem. Let me show show the code. He has pretty standard Spring application (not using Spring Boot). Uses more modern Java servlet Configuration based on Spring’s AbstractAnnotationConfigDispatcherServletInitializer. import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer; public class AppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer { @Override protected Class[] getRootConfigClasses() { return new Class[]{SecurityConfig.class}; } @Override protected Class[] getServletConfigClasses() { return new Class[]{WebConfig.class}; } @Override protected String[] getServletMappings() { return new String[]{"/"}; } } As you can see, there are two configuration classes: SecurityConfig – holds Spring Security configuration WebConfig – main Spring’s IoC container configuration package net.lkrnac.blog.dontscanconfigurations; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Configuration; import org.springframework.security.config.annotation.authentication.builders.AuthenticationManagerBuilder; import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter; import org.springframework.security.config.annotation.web.servlet.configuration.EnableWebMvcSecurity; @Configuration @EnableWebMvcSecurity public class SecurityConfig extends WebSecurityConfigurerAdapter { @Autowired public void configureGlobal(AuthenticationManagerBuilder auth) throws Exception { System.out.println("Spring Security init..."); auth .inMemoryAuthentication() .withUser("user").password("password").roles("USER"); } } import org.springframework.context.annotation.ComponentScan; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.EnableWebMvc; import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter; @Configuration @EnableWebMvc @ComponentScan(basePackages = "net.lkrnac.blog.dontscanconfigurations") public class WebConfig extends WebMvcConfigurerAdapter { } Pay attention to the component scanning in WebConfig. It is scanning package where all three classes are located. When you run this on servlet container, text “Spring Security init…” is written to console twice. It mean mean SecurityConfig configuration is loaded twice. It was loaded During creation of root context in method AppInitializer.getRootConfigClasses() By component scan in class WebConfig. This instance is created as part of servlet context creation in method AppInitializer.getServletConfigClasses(). Why? I found this explanation in Spring’s documentation: Remember that @Configuration classes are meta-annotated with @Component, so they are candidates for component-scanning! So this is feature of Spring and therefore we want to avoid component scanning of Spring @Configuration used by Servlet configuration. Brett Ryan independently found this problem and showed his solution in mentioned Stack Overflow question: @ComponentScan(basePackages = "com.acme.app", excludeFilters = { @Filter(type = ASSIGNABLE_TYPE, value = { WebConfig.class, SecurityConfig.class }) }) I don’t like this solution. Annotation is too verbose for me. Also some developer can create new @Configuration class and forget to include it into this filter. I would rather specify special package that would be excluded from Spring’s component scanning. Even better solution for this problem would be for me not to define separate contexts and rather use only servlet context as described in Spring Reference Documentation. Far most optimal solution is using Spring Boot with embedded servlet container, where you don’t need to define AbstractAnnotationConfigDispatcherServletInitializer at all. I created sample project on Github so that you can play with it.

Originally authored by Artem Bilan on the SpringSource blog Dear Spring Community! Just after the Spring Integration Java DSL 1.0 GA release announcement I want to introduce the Spring Integration Java DSL to you as a line by line tutorial based on the classic Cafe Demo integration sample. We describe here Spring Boot support, Spring Framework Java and Annotation configuration, the IntegrationFlow feature and pay tribute to Java 8 Lambdasupport which was an inspiration for the DSL style. Of course, it is all backed by the Spring Integration Core project. But, before we launch into the description of the Cafe demonstration app here's a shorter example just to get started... @Configuration @EnableAutoConfiguration @IntegrationComponentScan public class Start { public static void main(String[] args) throws InterruptedException { ConfigurableApplicationContext ctx = SpringApplication.run(Start.class, args); List strings = Arrays.asList("foo", "bar"); System.out.println(ctx.getBean(Upcase.class).upcase(strings)); ctx.close(); } @MessagingGateway public interface Upcase { @Gateway(requestChannel = "upcase.input") Collection upcase(Collection strings); } @Bean public IntegrationFlow upcase() { return f -> f .split() // 1 .transform(String::toUpperCase) // 2 .aggregate(); // 3 } } We will leave the description of the infrastructure (annotations etc) to the main cafe flow description. Here, we want you to concentrate on the last @Bean, the IntegrationFlow as well as the gateway method which sends messages to that flow. In the main method we send a collection of strings to the gateway and print the results to STDOUT. The flow first splits the collection into individual Strings (1); each string is then transformed to upper case (2) and finally we re-aggregate them back into a collection (3) Since that's the end of the flow, the framework returns the result of the aggregation back to the gateway and the new payload becomes the return value from the gateway method. The equivalent XML configuration might be... or... Cafe Demo The purpose of the Cafe Demo application is to demonstrate how Enterprise Integration Patterns (EIP) can be used to reflect the order-delivery scenario in a real life cafe. With this application, we handle several drink orders - hot and iced. After running the application we can see in the standard output (System.out.println) how cold drinks are prepared quicker than hot. However the delivery for the whole order is postponed until the hot drink is ready. To reflect the domain model we have several classes: Order, OrderItem, Drink andDelivery. They all are mentioned in the integration scenario, but we won't analyze them here, because they are simple enough. The source code for our application is placed only in a single class; significant lines are annotated with a number corresponding to the comments, which follow: @SpringBootApplication // 1 @IntegrationComponentScan // 2 public class Application { public static void main(String[] args) throws Exception { ConfigurableApplicationContext ctx = SpringApplication.run(Application.class, args);// 3 Cafe cafe = ctx.getBean(Cafe.class); // 4 for (int i = 1; i <= 100; i++) { // 5 Order order = new Order(i); order.addItem(DrinkType.LATTE, 2, false); //hot order.addItem(DrinkType.MOCHA, 3, true); //iced cafe.placeOrder(order); } System.out.println("Hit 'Enter' to terminate"); // 6 System.in.read(); ctx.close(); } @MessagingGateway // 7 public interface Cafe { @Gateway(requestChannel = "orders.input") // 8 void placeOrder(Order order); // 9 } private AtomicInteger hotDrinkCounter = new AtomicInteger(); private AtomicInteger coldDrinkCounter = new AtomicInteger(); // 10 @Bean(name = PollerMetadata.DEFAULT_POLLER) public PollerMetadata poller() { // 11 return Pollers.fixedDelay(1000).get(); } @Bean public IntegrationFlow orders() { // 12 return f -> f // 13 .split(Order.class, Order::getItems) // 14 .channel(c -> c.executor(Executors.newCachedThreadPool()))// 15 .route(OrderItem::isIced, mapping -> mapping // 16 .subFlowMapping("true", sf -> sf // 17 .channel(c -> c.queue(10)) // 18 .publishSubscribeChannel(c -> c // 19 .subscribe(s -> // 20 s.handle(m -> sleepUninterruptibly(1, TimeUnit.SECONDS)))// 21 .subscribe(sub -> sub // 22 .transform(item -> Thread.currentThread().getName() + " prepared cold drink #" + this.coldDrinkCounter.incrementAndGet() + " for order #" + item.getOrderNumber() + ": " + item) // 23 .handle(m -> System.out.println(m.getPayload())))))// 24 .subFlowMapping("false", sf -> sf // 25 .channel(c -> c.queue(10)) .publishSubscribeChannel(c -> c .subscribe(s -> s.handle(m -> sleepUninterruptibly(5, TimeUnit.SECONDS)))// 26 .subscribe(sub -> sub .transform(item -> Thread.currentThread().getName() + " prepared hot drink #" + this.hotDrinkCounter.incrementAndGet() + " for order #" + item.getOrderNumber() + ": " + item) .handle(m -> System.out.println(m.getPayload())))))) .transform(orderItem -> new Drink(orderItem.getOrderNumber(), orderItem.getDrinkType(), orderItem.isIced(), orderItem.getShots())) // 27 .aggregate(aggregator -> aggregator // 28 .outputProcessor(group -> // 29 new Delivery(group.getMessages() .stream() .map(message -> (Drink) message.getPayload()) .collect(Collectors.toList()))) // 30 .correlationStrategy(m -> ((Drink) m.getPayload()).getOrderNumber()), null) // 31 .handle(CharacterStreamWritingMessageHandler.stdout()); // 32 } } Examining the code line by line... 1. @SpringBootApplication This new meta-annotation from Spring Boot 1.2. Includes @Configuration and@EnableAutoConfiguration. Since we are in a Spring Integration application and Spring Boot has auto-configuration for it, the @EnableIntegration is automatically applied, to initialize the Spring Integration infrastructure including an environment for the Java DSL -DslIntegrationConfigurationInitializer, which is picked up by theIntegrationConfigurationBeanFactoryPostProcessor from /META-INF/spring.factories. 2. @IntegrationComponentScan The Spring Integration analogue of @ComponentScan to scan components based on interfaces, (the Spring Framework's @ComponentScan only looks at classes). Spring Integration supports the discovery of interfaces annotated with @MessagingGateway (see #7 below). 3. ConfigurableApplicationContext ctx = SpringApplication.run(Application.class, args); The main method of our class is designed to start the Spring Boot application using the configuration from this class and starts an ApplicationContext via Spring Boot. In addition, it delegates command line arguments to the Spring Boot. For example you can specify --debug to see logs for the boot auto-configuration report. 4. Cafe cafe = ctx.getBean(Cafe.class); Since we already have an ApplicationContext we can start to interact with application. AndCafe is that entry point - in EIP terms a gateway. Gateways are simply interfaces and the application does not interact with the Messaging API; it simply deals with the domain (see #7 below). 5. for (int i = 1; i <= 100; i++) { To demonstrate the cafe "work" we intiate 100 orders with two drinks - one hot and one iced. And send the Order to the Cafe gateway. 6. System.out.println("Hit 'Enter' to terminate"); Typically Spring Integration application are asynchronous, hence to avoid early exit from themain Thread we block the main method until some end-user interaction through the command line. Non daemon threads will keep the application open but System.read()provides us with a mechanism to close the application cleanly. 7. @MessagingGateway The annotation to mark a business interface to indicate it is a gateway between the end-application and integration layer. It is an analogue of component from Spring Integration XML configuration. Spring Integration creates a Proxy for this interface and populates it as a bean in the application context. The purpose of this Proxy is to wrap parameters in a Message object and send it to the MessageChannel according to the provided options. 8. @Gateway(requestChannel = "orders.input") The method level annotation to distinct business logic by methods as well as by the target integration flows. In this sample we use a requestChannel reference of orders.input, which is a MessageChannel bean name of our IntegrationFlow input channel (see below #13). 9. void placeOrder(Order order); The interface method is a central point to interact from end-application with the integration layer. This method has a void return type. It means that our integration flow is one-wayand we just send messages to the integration flow, but don't wait for a reply. 10. private AtomicInteger hotDrinkCounter = new AtomicInteger(); private AtomicInteger coldDrinkCounter = new AtomicInteger(); Two counters to gather the information how our cafe works with drinks. 11. @Bean(name = PollerMetadata.DEFAULT_POLLER) public PollerMetadata poller() { The default poller bean. It is a analogue of component from Spring Integration XML configuration. Required for endpoints where the inputChannelis a PollableChannel. In this case, it is necessary for the two Cafe queues - hot and iced (see below #18). Here we use the Pollers factory from the DSL project and use its method-chain fluent API to build the poller metadata. Note that Pollers can be used directly from an IntegrationFlow definition, if a specific poller (rather than the default poller) is needed for an endpoint. 12. @Bean public IntegrationFlow orders() { The IntegrationFlow bean definition. It is the central component of the Spring Integration Java DSL, although it does not play any role at runtime, just during the bean registration phase. All other code below registers Spring Integration components (MessageChannel,MessageHandler, EventDrivenConsumer, MessageProducer, MessageSource etc.) in theIntegrationFlow object, which is parsed by the IntegrationFlowBeanPostProcessor to process those components and register them as beans in the application context as necessary (some elements, such as channels may already exist). 13. return f -> f The IntegrationFlow is a Consumer functional interface, so we can minimize our code and concentrate just only on the integration scenario requirements. Its Lambda acceptsIntegrationFlowDefinition as an argument. This class offers a comprehensive set of methods which can be composed to the chain. We call these EIP-methods, because they provide implementations for EI patterns and populate components from Spring Integration Core. During the bean registration phase, the IntegrationFlowBeanPostProcessor converts this inline (Lambda) IntegrationFlow to a StandardIntegrationFlow and processes its components. The same we can achieve using IntegrationFlows factory (e.g.IntegrationFlow.from("channelX"). ... .get()), but we find the Lambda definition more elegant. An IntegrationFlow definition using a Lambda populates DirectChannel as an inputChannel of the flow and it is registered in the application context as a bean with the name orders.input in this our sample (flow bean name + ".input"). That's why we use that name for the Cafe gateway. 14. .split(Order.class, Order::getItems) Since our integration flow accepts message through the orders.input channel, we are ready to consume and process them. The first EIP-method in our scenario is .split(). We know that the message payload from orders.input channel is an Order domain object, so we can simply use its type here and use the Java 8 method-reference feature. The first parameter is a type of message payload we expect, and the second is a method reference to the getItems() method, which returns Collection. So, this performs thesplit EI pattern, when we send each collection entry as a separate message to the next channel. In the background, the .split() method registers a MethodInvokingSplitterMessageHandler implementation and the EventDrivenConsumer for thatMessageHandler, and wiring in the orders.input channel as the inputChannel. 15. .channel(c -> c.executor(Executors.newCachedThreadPool())) The .channel() EIP-method allows the specification of concrete MessageChannels between endpoints, as it is done via output-channel/input-channel attributes pair with Spring Integration XML configuration. By default, endpoints in the DSL integration flow definition are wired with DirectChannels, which get the bean names based on theIntegrationFlow bean name and index in the flow chain. In this case we use anotherLambda expression, which selects a specific MessageChannel implementation from itsChannels factory and configures it with the fluent API. The current channel here is anExecutorChannel, to allow to distribute messages from the splitter to separateThreads, to process them in parallel in the downstream flow. 16. .route(OrderItem::isIced, mapping -> mapping The next EIP-method in our scenario is .route(), to send hot/iced order items to different Cafe kitchens. We again use here a method reference (isIced()) to get theroutingKey from the incoming message. The second Lambda parameter represents arouter mapping - something similar to sub-element for the component from Spring Integration XML configuration. However since we are using Java we can go a bit further with its Lambda support! The Spring Integration Java DSL introduced thesubflow definition for routers in addition to traditional channel mapping. Each subflow is executed depending on the routing and, if the subflow produces a result, it is passed to the next element in the flow definition after the router. 17. .subFlowMapping("true", sf -> sf Specifies the integration flow for the current router's mappingKey. We have in this samples two subflows - hot and iced. The subflow is the same IntegrationFlow functional interface, therefore we can use its Lambda exactly the same as we do on the top levelIntegrationFlow definition. The subflows don't have any runtime dependency with its parent, it's just a logical relationship. 18. .channel(c -> c.queue(10)) We already know that a Lambda definition for the IntegrationFlow starts from[FLOW_BEAN_NAME].input DirectChannel, so it may be a question "how does it work here if we specify .channel() again?". The DSL takes care of such a case and wires those two channels with a BridgeHandler and endpoint. In our sample, we use here a restrictedQueueChannel to reflect the Cafe kitchen busy state from real life. And here is a place where we need that global poller for the next endpoint which is listening on this channel. 19. .publishSubscribeChannel(c -> c The .publishSubscribeChannel() EIP-method is a variant of the .channel() for aMessageChannels.publishSubscribe(), but with the .subscribe() option when we can specify subflow as a subscriber to the channel. Right, subflow one more time! So, subflows can be specified to any depth. Independently of the presence .subscribe() subflows, the next endpoint in the parent flow is also a subscriber to this .publishSubscribeChannel(). Since we are in the .route() subflow already, the last subscriber is an implicit BridgeHandlerwhich just pops the message to the top level - to a similar implicit BridgeHandler to pop message to the next .transform() endpoint in the main flow. And one more note about this current position of our flow: the previous EIP-method is .channel(c -> c.queue(10)) and this one is for MessageChannel too. So, they are again tied with an implicit BridgeHandleras well. In a real application we could avoid this .publishSubscribeChannel() just with the single .handle() for the Cafe kitchen, but our goal here to cover DSL features as much as possible. That's why we distribute the kitchen work to several subflows for the samePublishSubscribeChannel. 20. .subscribe(s -> The .subscribe() method accepts an IntegrationFlow as parameter, which can be specified as Lambda to configure subscriber as subflow. We use here several subflow subscribers to avoid multi-line Lambdas and cover some DSL as we as Spring Integration capabilities. 21. s.handle(m -> sleepUninterruptibly(1, TimeUnit.SECONDS))) Here we use a simple .handle() EIP-method just to block the current Thread for some timeout to demonstrate how quickly the Cafe kitchen prepares a drink. Here we use Google Guava Uninterruptibles.sleepUninterruptibly, to avoid using a try...catch block within the Lambda expression, although you can do that and your Lambda will be multi-line. Or you can move that code to a separate method and use it here as method reference. Since we don't use any Executor on the .publishSubscribeChannel() all subscribers will beperformed sequentially on the same Thread; in our case it is one of TaskScheduler's Threads from poller on the previous QueueChannel. That's why this sleep blocks all downstream process and allows to demonstrate the busy state for that restricted to 10QueueChannel. 22. .subscribe(sub -> sub The next subflow subscriber which will be performed only after that sleep with 1 second foriced drink. We use here one more subflow because .handle() of previous one is one-way with the nature of the Lambda for MessageHandler. That's why, to go ahead with process of our whole flow, we have several subscribers: some of subflows finish after their work and don't return anything to the parent flow. 23. .transform(item -> Thread.currentThread().getName() + " prepared cold drink #" + this.coldDrinkCounter.incrementAndGet() + " for order #" + item.getOrderNumber() + ": " + item) The transformer in the current subscriber subflow is to convert the OrderItem to the friendly STDOUT message for the next .handle. Here we see the use of generics with the Lambda expression. This is implemented using the GenericTransformer functional interface. 24. .handle(m -> System.out.println(m.getPayload()))))) The .handle() here just to demonstrate how to use Lambda expression to print thepayload to STDOUT. It is a signal that our drink is ready. After that the final (implicit) subscriber to the PublishSubscribeChannel just sends the message with the OrderItemto the .transform() in the main flow. 25. .subFlowMapping("false", sf -> sf The .subFlowMapping() for the hot drinks. Actually it is similar to the previous iceddrinks subflow, but with specific hot business logic. 26. s.handle(m -> sleepUninterruptibly(5, TimeUnit.SECONDS))) The sleepUninterruptibly for hot drinks. Right, we need more time to boil the water! 27. .transform(orderItem -> new Drink(orderItem.getOrderNumber(), orderItem.getDrinkType(), orderItem.isIced(), orderItem.getShots())) The main OrderItem to Drink transformer, which is performed when the .route()subflow returns its result after the Cafe kitchen subscribers have finished preparing the drink. 28. .aggregate(aggregator -> aggregator The .aggregate() EIP-method provides similar options to configure anAggregatingMessageHandler and its endpoint, like we can do with the component when using Spring Integration XML configuration. Of course, with the Java DSL we have more power to configure the aggregator just in place, without any other extra beans. And Lambdas come to the rescue again! From the Cafe business logic perspective we compose theDelivery for the initial Order, since we .split() the original order to the OrderItems near the beginning. 29. .outputProcessor(group -> The .outputProcessor() of the AggregatorSpec allows us to emit a custom result after aggregator completes the group. It's an analogue of ref/method from the component or the @Aggregator annotation on a POJO method. Our goal here to compose aDelivery for all Drinks. 30. new Delivery(group.getMessages() .stream() .map(message -> (Drink) message.getPayload()) .collect(Collectors.toList()))) As you see we use here the Java 8 Stream feature for Collection. We iterate over messages from the released MessageGroup and convert (map) each of them to its Drinkpayload. The result of the Stream (.collect()) (a list of Drinks) is passed to theDelivery constructor. The Message with this new Delivery payload is sent to the next endpoint in our Cafe scenario. 31. .correlationStrategy(m -> ((Drink) m.getPayload()).getOrderNumber()), null) The .correlationStrategy() Lambda demonstrates how we can customize an aggregator behaviour. Of course, we can rely here just only on a built-in SequenceDetails from Spring Integration, which is populated by default from .split() in the beginning of our flow to each split message, but the Lambda sample for the CorrelationStrategy is included for illustration. (With XML, we could have used a correlation-expression or a customCorrelationStrategy). The second argument in this line for the .aggregate() EIP-method is for the endpointConfigurer to customize options like autoStartup,requiresReply, adviceChain etc. We use here null to show that we rely on the default options for the endpoint. Many of EIP-methods provide overloaded versions with and withoutendpointConfigurer, but .aggregate() requires an endpoint argument, to avoid an explicit cast for the AggregatorSpec Lambda argument. 32. .handle(CharacterStreamWritingMessageHandler.stdout()); It is the end of our flow - the Delivery is delivered to the client! We just print here the message payload to STDOUT using out-of-the-boxCharacterStreamWritingMessageHandler from Spring Integration Core. This is a case to show how existing components from Spring Integration Core (and its modules) can be used from the Java DSL. Well, we have finished describing the Cafe Demo sample based on the Spring Integration Java DSL. Compare it with XML sample to get more information regarding Spring Integration. This is not an overall tutorial to the DSL stuff. We don't review here theendpointConfigurer options, Transformers factory, the IntegrationComponentSpechierarchy, the NamespaceFactories, how we can specify several IntegrationFlow beans and wire them to a single application etc., see the Reference Manual for more information. At least this line-by-line tutorial should show you Spring Integration Java DSL basics and its seamless fusion between Spring Framework Java & Annotation configuration, Spring Integration foundation and Java 8 Lambda support! Also see the si4demo to see the evolution of Spring Integration including the Java DSL, as shown at the 2014 SpringOne/2GX Conference. (Video should be available soon). As always, we look forward to your comments and feedback (StackOverflow (spring-integration tag), Spring JIRA, GitHub) and we very much welcome contributions! P.S. Even if this tutorial is fully based on the Java 8 Lambda support, we don't want to miss pre Java 8 users, we are going to provide similar non-Lambda blog post. Stay tuned!

I often get asked what it takes to be an effective product manager or product owner, which product skills the individuals should have, and how a company can strengthen its product management function. Answering these questions requires an understanding of what effective product management looks like in the digital age. The following picture shows how I view product management: It depicts a product management framework that consists of six core knowledge areas and by six supporting ones. The core areas are orange and placed centrally. The supporting ones are purple and located at the edge of the circle. You can download the picture for free by simply clicking on it or from romanpichler.com/tools/product-management-framework. The core areas are particularly important for doing a great job as a product manager or product owner. You should hence strive to become knowledgeable in all of them. The supporting areas are also important for your work, especially when you manage commercial products, but generally not as crucial. If the product management framework with its knowledge areas feels overwhelming then don’t worry: Product management is a complex and demanding discipline that is not easy to master. It takes time and effort to become a competent product manager or product owner. The good news is that you can use the framework to spot gaps in your skill set so you can address them. The Core Knowledge Areas Vision and Leadership: Working as an effective product managers or product owner requires vision and leadership skills. You should be able to establish a shared vision, set realistic goals, and describe the benefits your product should deliver. You should be able to actively listen to others and negotiate to reach agreement and get buy-in. At the same time, you should not shy away from making the right product decisions even if they are tough and do not please everyone. You should be able to manage the stakeholders including customers and users, senior management, development, marketing, sales, support, and other business groups that have to contribute to the product success. You should be able to effectively communicate with and influence them. You be comfortable working with a broad range of people from diverse backgrounds including a cross-functional development team. Product Lifecycle Management: Managing a product successfully involves more than getting it built and released. You should understand the product lifecycle with its stages and the key events in the life of your product including launch, product-market fit, and end of sales; you should know how the lifecycle helps you maximise the benefits your product creates across its entire life; this includes the lifecycle’s impact on the product performance (revenue and profits), the product goals, the pricing and the marketing strategy; the options to revive growth as your product matures and growth starts to stagnate; and the process best suited for each lifecycle stage. (An iterative, Lean Startup and Scrum-based process tends to beneficial while your product is young; Kanban is usually preferable when your product starts to mature.) Product Strategy and Market Research: Your product exists to serve a market or market segment, a group of people whose need the product addresses. You therefore should be able to identify your target users and customers and segment the market; you should be able to clearly state the value proposition of your product, why people would want to use and buy it and why your product does a great job at creating value for them. You should be able to carry out a competitor analysis to understand their respective strengths and weaknesses; you should be able to position your product, and determine the values the brand needs to communicate. You should be able to perform the necessary market research work to test your ideas and assumptions about the market segment and the value proposition. This includes qualitative and quantitative methods including problem interviews, direct observations, and employing minimum viable products (MVPs); you should be able to leverage data to make the right decisions. This includes using an analytics tool, analysing the data effectively, and deciding if you should pivot and change your strategy or if you should persevere and refine it. Business Model and Financials: To provide an investment incentive for your company and to make developing and providing the product sustainable, you have to be able to determine the value the product creates for your firm. You should be able to formulate and prioritise business goals, for instance, enter a new market, meet a revenue or profit goal, save cost, or develop the brand. You should be able to describe how your product’s value proposition is monetised and capture how the business model works including the revenue sources and the main cost factors. You should also be able to create a financial forecast or business case that describes when a break-even is likely to occur and when your product may become profitable. In practice, you may want to partner with a colleague from the finance department to carry out this work. Product Roadmap: Many people have to contribute to the success of a digital product. To help them do their work and to provide visibility of how your product is likely to evolve, you should be able to create and use a product roadmap. This includes formulating realistic product goals (benefits), metrics and key performance indicators (KPIs), release dates or timeframes, and key features (deliverables or results). You should be clear on the relationship between the product strategy and the product roadmap. You should be able to formulate a go-to-market strategy and capture it in your roadmap. You should understand when the roadmap should be reviewed and changed. User Experience and Product Backlog: A great product has to offer a great user experience (UX). You should be able to describe the desired user experience. This includes describing users and customer as personas, capturing the user interaction, the visual design, the functional and the non-functional aspects of your product together with the help of the cross-functional team (a UX/UI expert should be part of the team). You should be able to create scenarios, epics, user stories, storyboards, workflow diagrams and storymaps, and be able to work with user interface sketches and mock-ups. You should be able to stock and manage the product backlog, prioritise it effectively, and select sprint goals. You should know how to understand if you develop a product with the right features and the right UX, how to test the appropriate aspects of your product and how to collect the relevant feedback and data. This includes the ability to perform product demoes, solution interviews, usability tests, A/B tests, and direct observation. You should be able to use an analytics tool to retrieve the relevant data and be able to analyse it effectively. You be able to change (or “groom”) the product backlog using the newly gained insights. Continue reading... The Supporting Knowledge Areas General Market Knowledge: Understand who your current customers and users are, what product you offer them today including their value proposition and business model, what competitors you have, how big your market share currently is, and which market segments you serve well. Development/Technologies: Be a competent partner for development/IT/engineering, have an interest in software technologies, be comfortable collaborating with a cross-functional technical team. Marketing: Be a respected partner for (product) marketing; be able to help select the right select the right marketing channels and to determine the right marketing mix; help marketing with creating the marketing collateral. Sales and Support: Be a respected partner for sales and support; be able to help select the right sales channels and create the sales collateral and training. Project/Release management: Be able to determine the primary success factor for a major release/product version and to steer the development project; be able to determine the project progress to forecast the progress, for instance, using a release burndown chart; be able to work with the Definition of Done; be able to trade-off scope, time, and budget. Process: Have a good understanding of ideation and innovation processes to generate and select ideas and to bring new products and new features to life. These should include Customer Development/Lean Startup, Business Model Generation, Scrum, and Kanban. Defining Product Roles with the Framework My product management framework helps you define product roles and the skills and responsibilities they should have. Using the framework, I can, for instance, define the role of a product owner in the following way: As the picture above shows, a product owner should have strategic product management skills such as product strategy and roadmapping as well as tactical ones (UX and product backlog). I have circled the areas, which are required by Scrum – the framework in which the role originated – in dark orange. The other areas are necessary to allow the product owner to do a great job and achieve product success even though they are not mandated by Scrum. You may, of course, disagree with my take on the product owner role and may want to use the framework to capture your definition of the role. Another example of how you can apply the framework is the description of the role of a tech product manager, a product manager who looks after a technical product and requires more in-depth technology/development skills, as the following picture illustrates. For instance, one of my clients is a major games development company, which has its own in-house developed physics engine, a complex piece of software that does all the clever animation. The product owner of the physics engine is a former developer. This makes sense, as the individual requires a detailed technical knowledge about the product and has to be able to communicate effectively with the users, the game developers. If you work as a product manager who looks after digital products that are developed and used in-house, for instance, a finance or HR application, then you probably have to tailor the supporting areas as the following picture shows: In the picture above, I have removed “Marketing” and replaced “Sales and Support” with “Operations”. I have kept “General Market Knowledge” as it is desirable for the product manager of a finance application to understand the market, that is, how the finance group works, what problems people struggle with, which products they use, and so forth. Determining Learning Measures with the Framework You can also use the product management framework to identify gaps in your skill set. Use the knowledge areas and reflect on your own knowledge. Then identify the areas where you lack some knowledge and skills, as I have done in the picture below by high-lightening the areas, which product owners often need to strengthen in my experience. Then rank them by determining how much the lack of knowledge is preventing you from doing a great job. For instance, a lack of product lifecycle management and product roadmap skills may be hurting you most if you manage a product that is in the growth stage. Finally identify how you best close the gap, for instance, reading one or more books, or blogs, attending a training course, finding someone to mentor or coach you, forming a community of practice with your fellow product managers or product owners to share knowledge and support each other. You can do the same exercise for a group of product managers or product owners to identify learning measure for the entire function. Learn More You can learn more about specific areas such as vision and leadership, product strategy and market research, product roadmap, or user experience and product backlog by attending one of my training courses. I also teach my courses onsite and in from of interactive virtual training sessions. If you would like me to help you apply the framework, define roles, or identify the right learning and development measures for product managers and product owners, then please contact me.

this article represents different scenarios related with xss (cross-site scripting) and how to handle them appropriately using angularjs features such as sce ($sceprovider) and sanitize service ($sanitizeprovider) . please feel free to comment/suggest if i missed to mention one or more important points. also, sorry for the typos. following are the key xss-related scenarios described later in this article: escape html completely insert html in secure way while ignoring elements such as “script”. this is as well dangerous and could deface your website, if not taken care, especially with “img” tag. trust and insert entire html; this is dangerous and could easily end-up defacing your website escape html using ng-bind directive in case you want to escape html in entireity, you may want to use ng-bind directive. all it does is escape the html elements and print it as it is. following code demonstrates the ng-bind directive usage. angularjs xss demo test ng-bind directive: note that html text is entered as it is. {{hellomessage} following diagram demonstrates the above. pay attention to the html code entered in the text field. it is printed as it is, on to the html page. insert html in secure way, while ignoring elements such as “script”, using ng-bind-html directive this is key to solving xss attacks. that said, one should still take care of elements such as “img” ( included as part of white-list; void elements) as it could display any image (including illegal ones) on your webpage, thus, defacing your webpage . using ng-bind-html directive, javascript script tag such as “script” could be ignored straight-away. ng-bind-html directive evaluates the expression and inserts the resulting html into the element in a secure way. for cases where user inputs could consist of html (such as comments), the inclusion of ng-bind-html directive would ensure that the text is sanitize against a white-list of safe html tokens. the whitelist of safe tokens is coded as part of $sanitize module and mentioned below. following is included in the safe list (taken directly from the source code): void elements : area,br,col,hr,img,wbr. the details of same could be found at http://dev.w3.org/html5/spec/overview.html#void-elements block element : address,article,aside,blockquote,caption,center,del,dir,div,dl,figure,figcaption,footer,h1,h2,h3,h4, h5,h6,header,hgroup,hr,ins,map,menu,nav,ol,pre,script,section,table,ul inline elements : a,abbr,acronym,b,bdi,bdo,big,br,cite,code,del,dfn,em,font,i,img,ins,kbd,label,map,mark,q,ruby, rp,rt,s,samp,small,span,strike,strong,sub,sup,time,tt,u,var end tag elements : colgroup,dd,dt,li,p,tbody,td,tfoot,th,thead,tr,rp,rt. the details of same could be found at http://dev.w3.org/html5/spec/overview.html#optional-tags following are two elements which are escaped as it is in untrusted category . in case, you want to show it, you would have to use $sce service and call trustashtml method for angular to execute below-mentioned elements. script style following represents code sample demonstrating the ng-bind-html directive usage. angularjs xss demo test ng-bind-html directive: note that image is displayed appropriately as a result of text entered in the text field. following image demonstrates how it looks like when entering html code in textfield that is inserted into dom in a secure way. pay attention to “img” element which is a part of void elements in above list. as the code is entered in the textfield, the image appeared as “img” is in trusted list (white-list) trust and insert entire html warning: this is dangerous and could easily end-up defacing your website . only when you know and are doubly sure, you should use trustashtml. in case, you are confident that the text content could be trusted, you could use $sce service and call trustashtml method which then inserts entire html into the dom. pay attention to the html and javascript code snippet where $sce service is used to invoke trustashtml method to trust the html code. in that case, one code such as “” is inserted, it ended up painting already existing html element. this may not be healthy. one could change the background images with illegal images that way. ng-bind directive: note that html text is entered as it is. {{hellomessage} note that script tag is executed as well. following image demonstrates how it looks like when entering html style code in textfield that is inserted into dom . as a result, the other html element is painted in red as shown below. in scenarios where a hacker could insert an style element with background, this could show-up unwanted background and bring bad experience for the end users. entire code – cut/copy and paste and play angularjs xss demo test ng-bind directive: note that html text is entered as it is. {{hellomessage} note that script tag is executed as well. ng-bind-html directive: note that image is displayed appropriately as a result of text entered in the text field.

this article represents top 6 popular angularjs topics that has been used most by the angularjs developer community to date. the inference is derived based on number of tagged discussions happening on stackoverflow . clearly, “directive” is the winner and attracts most of them all. the article presents my thoughts on why these topics have been most popular. please feel free to comment/suggest if i missed to mention one or more important points. also, sorry for the typos. following is the list of top 6 popular topics: directives scope object ng-repeat angular ui & bootstrap routing service following plot demonstrates the popularity of different feature/topics in relation with angularjs. angularjs topics popularity inference : some of the following could as well be inferred from the above data/plot. three features which have been most used by the developers and therefore, should be key reasons why you would also want to use angular in next project are following: directives routing ng-repeat one of the pain point (or shortcoming) that have been talked most by the angular developers is the ui widgets related support by angular. this is where most of them have jumped to angular ui and bootstrap. the topic/concept that has intrigued most to several developers is scope object. thoughts on why these topics may be most popular following are top 6 popular topics in angularjs discussed on forums such as stackoverflow: directives : this is, no doubt, the most popular and powerful feature of angularjs directives as also indicated by count of discussion threads posted on stackoverflow as of today. the power of directives lies in the following and this is why it is the most popular topic of angularjs. re-usability : once created a directive as part of a module, all that one need to do to use the directive is include the module as a dependency when defining new module and define the directives wherever required on the page. usability : owing to the fact that one could give intuitive names to directives, directive enhances the readability and understandability of code by a notch. greater adherence to dry principle : the aspect of templating makes directive a very attractive feature. it does reduce the duplication of code as same html template code could be used at several places without the need to write the code in html file. scope object : this is second most popular topic found based on the discussion count. rightfully expected as well! the whole notion of scope object and how it is key to dependency injection makes it one of the most powerful as well as tricky concept of angularjs. also, this is one of the topic which raised the barrier to entry for angularjs and contributed in making steep learning curve for developers. that said, scope is going to r.i.p in angular 2.0 which could be seen as a good sign for those who always struggled with scope object. ng-repeat : the ng-repeat feature brings power to angularjs from the fact that it is one of the feature that removed the need of server-side code required to repeat the html code over multiple iterations. with ng-repeat, one could easily repeat html code multiple times. angular ui & bootstrap : one of the shortcoming of angularjs for good or bad is its inability to be one and all solution to create some great ui along with powerful eventing feature. for creating fancy or great looking ui, one would still have to go to ui frameworks such as bootstrap, kendo-ui etc. this is where people have been looking for angularui and bootstrap. angularui comes with attractive feature set for enhanced routing, grid util, angularjs code editor plugins, bootstrap module etc. routing : routing feature is key to creating single page application. one of key reason why angularjs is very popular is the ease with which one could create single-page application using it. and, routing feature makes it all happen. no doubt, this is why many developers have been looking for it. service : service feature helps one to create reusable components in an angular module. these services could then be injected in another modules using dependency injection feature. the service could be injected in one of the following components: controllers services doing a quick recap, one may recall that for creating a service, one could use factory recipe method and define service that way. you could know details about creating a custom service on our another page dedicated on this.

Thread Pools are very important to execute synchronous & asynchronous processes. This article shows how to develop and monitor Thread Pool Services by using Spring. Creating Thread Pool has been explained via two alternative methods. Used Technologies : JDK 1.6.0_21 Spring 3.0.5 Maven 3.0.2 STEP 1 : CREATE MAVEN PROJECT A maven project is created as below. (It can be created by using Maven or IDE Plug-in). STEP 2 : LIBRARIES Spring dependencies are added to Maven’ s pom.xml. ? org.springframework spring-core ${spring.version} org.springframework spring-context ${spring.version} For creating runnable-jar, below plugin can be used. ? org.apache.maven.plugins maven-shade-plugin 1.3.1 package shade com.otv.exe.Application META-INF/spring.handlers META-INF/spring.schemas STEP 3 : CREATE TASK CLASS A new TestTask Class is created by implementing Runnable Interface. This class shows to be executed tasks. ? package com.otv.task; import org.apache.log4j.Logger; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public class TestTask implements Runnable { private static Logger log = Logger.getLogger(TestTask.class); String taskName; public TestTask() { } public TestTask(String taskName) { this.taskName = taskName; } public void run() { try { log.debug(this.taskName + " : is started."); Thread.sleep(10000); log.debug(this.taskName + " : is completed."); } catch (InterruptedException e) { log.error(this.taskName + " : is not completed!"); e.printStackTrace(); } } @Override public String toString() { return (getTaskName()); } public String getTaskName() { return taskName; } public void setTaskName(String taskName) { this.taskName = taskName; } } STEP 4 : CREATE TestRejectedExecutionHandler CLASS TestRejectedExecutionHandler Class is created by implementing RejectedExecutionHandler Interface. If there is no idle thread and queue overflows, tasks will be rejected. This class handles rejected tasks. ? package com.otv.handler; import java.util.concurrent.RejectedExecutionHandler; import java.util.concurrent.ThreadPoolExecutor; import org.apache.log4j.Logger; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public class TestRejectedExecutionHandler implements RejectedExecutionHandler { private static Logger log = Logger.getLogger(TestRejectedExecutionHandler.class); public void rejectedExecution(Runnable runnable, ThreadPoolExecutor executor) { log.debug(runnable.toString() + " : has been rejected"); } } STEP 5 : CREATE ITestThreadPoolExecutorService INTERFACE ITestThreadPoolExecutorService Interface is created. ? package com.otv.srv; import java.util.concurrent.ThreadPoolExecutor; import com.otv.handler.TestRejectedExecutionHandler; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public interface ITestThreadPoolExecutorService { public ThreadPoolExecutor createNewThreadPool(); public int getCorePoolSize(); public void setCorePoolSize(int corePoolSize); public int getMaxPoolSize(); public void setMaxPoolSize(int maximumPoolSize); public long getKeepAliveTime(); public void setKeepAliveTime(long keepAliveTime); public int getQueueCapacity(); public void setQueueCapacity(int queueCapacity); public TestRejectedExecutionHandler getTestRejectedExecutionHandler(); public void setTestRejectedExecutionHandler(TestRejectedExecutionHandler testRejectedExecutionHandler); } STEP 6 : CREATE TestThreadPoolExecutorService CLASS TestThreadPoolExecutorService Class is created by implementing ITestThreadPoolExecutorService Interface. This class creates a new Thread Pool. ? package com.otv.srv; import java.util.concurrent.ArrayBlockingQueue; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; import com.otv.handler.TestRejectedExecutionHandler; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public class TestThreadPoolExecutorService implements ITestThreadPoolExecutorService { private int corePoolSize; private int maxPoolSize; private long keepAliveTime; private int queueCapacity; TestRejectedExecutionHandler testRejectedExecutionHandler; public ThreadPoolExecutor createNewThreadPool() { ThreadPoolExecutor executor = new ThreadPoolExecutor(getCorePoolSize(), getMaxPoolSize(), getKeepAliveTime(), TimeUnit.SECONDS, new ArrayBlockingQueue(getQueueCapacity()), getTestRejectedExecutionHandler()); return executor; } public int getCorePoolSize() { return corePoolSize; } public void setCorePoolSize(int corePoolSize) { this.corePoolSize = corePoolSize; } public int getMaxPoolSize() { return maxPoolSize; } public void setMaxPoolSize(int maxPoolSize) { this.maxPoolSize = maxPoolSize; } public long getKeepAliveTime() { return keepAliveTime; } public void setKeepAliveTime(long keepAliveTime) { this.keepAliveTime = keepAliveTime; } public int getQueueCapacity() { return queueCapacity; } public void setQueueCapacity(int queueCapacity) { this.queueCapacity = queueCapacity; } public TestRejectedExecutionHandler getTestRejectedExecutionHandler() { return testRejectedExecutionHandler; } public void setTestRejectedExecutionHandler(TestRejectedExecutionHandler testRejectedExecutionHandler) { this.testRejectedExecutionHandler = testRejectedExecutionHandler; } } STEP 7 : CREATE IThreadPoolMonitorService INTERFACE IThreadPoolMonitorService Interface is created. ? package com.otv.monitor.srv; import java.util.concurrent.ThreadPoolExecutor; public interface IThreadPoolMonitorService extends Runnable { public void monitorThreadPool(); public ThreadPoolExecutor getExecutor(); public void setExecutor(ThreadPoolExecutor executor); } STEP 8 : CREATE ThreadPoolMonitorService CLASS ThreadPoolMonitorService Class is created by implementing IThreadPoolMonitorService Interface. This class monitors created thread pool. ? package com.otv.monitor.srv; import java.util.concurrent.ThreadPoolExecutor; import org.apache.log4j.Logger; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public class ThreadPoolMonitorService implements IThreadPoolMonitorService { private static Logger log = Logger.getLogger(ThreadPoolMonitorService.class); ThreadPoolExecutor executor; private long monitoringPeriod; public void run() { try { while (true){ monitorThreadPool(); Thread.sleep(monitoringPeriod*1000); } } catch (Exception e) { log.error(e.getMessage()); } } public void monitorThreadPool() { StringBuffer strBuff = new StringBuffer(); strBuff.append("CurrentPoolSize : ").append(executor.getPoolSize()); strBuff.append(" - CorePoolSize : ").append(executor.getCorePoolSize()); strBuff.append(" - MaximumPoolSize : ").append(executor.getMaximumPoolSize()); strBuff.append(" - ActiveTaskCount : ").append(executor.getActiveCount()); strBuff.append(" - CompletedTaskCount : ").append(executor.getCompletedTaskCount()); strBuff.append(" - TotalTaskCount : ").append(executor.getTaskCount()); strBuff.append(" - isTerminated : ").append(executor.isTerminated()); log.debug(strBuff.toString()); } public ThreadPoolExecutor getExecutor() { return executor; } public void setExecutor(ThreadPoolExecutor executor) { this.executor = executor; } public long getMonitoringPeriod() { return monitoringPeriod; } public void setMonitoringPeriod(long monitoringPeriod) { this.monitoringPeriod = monitoringPeriod; } } STEP 9 : CREATE Starter CLASS Starter Class is created. ? package com.otv.start; import java.util.concurrent.ThreadPoolExecutor; import org.apache.log4j.Logger; import com.otv.handler.TestRejectedExecutionHandler; import com.otv.monitor.srv.IThreadPoolMonitorService; import com.otv.monitor.srv.ThreadPoolMonitorService; import com.otv.srv.ITestThreadPoolExecutorService; import com.otv.srv.TestThreadPoolExecutorService; import com.otv.task.TestTask; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public class Starter { private static Logger log = Logger.getLogger(TestRejectedExecutionHandler.class); IThreadPoolMonitorService threadPoolMonitorService; ITestThreadPoolExecutorService testThreadPoolExecutorService; public void start() { // A new thread pool is created... ThreadPoolExecutor executor = testThreadPoolExecutorService.createNewThreadPool(); executor.allowCoreThreadTimeOut(true); // Created executor is set to ThreadPoolMonitorService... threadPoolMonitorService.setExecutor(executor); // ThreadPoolMonitorService is started... Thread monitor = new Thread(threadPoolMonitorService); monitor.start(); // New tasks are executed... for(int i=1;i<10;i++) { executor.execute(new TestTask("Task"+i)); } try { Thread.sleep(40000); } catch (Exception e) { log.error(e.getMessage()); } for(int i=10;i<19;i++) { executor.execute(new TestTask("Task"+i)); } // executor is shutdown... executor.shutdown(); } public IThreadPoolMonitorService getThreadPoolMonitorService() { return threadPoolMonitorService; } public void setThreadPoolMonitorService(IThreadPoolMonitorService threadPoolMonitorService) { this.threadPoolMonitorService = threadPoolMonitorService; } public ITestThreadPoolExecutorService getTestThreadPoolExecutorService() { return testThreadPoolExecutorService; } public void setTestThreadPoolExecutorService(ITestThreadPoolExecutorService testThreadPoolExecutorService) { this.testThreadPoolExecutorService = testThreadPoolExecutorService; } } STEP 10 : CREATE Application CLASS Application Class is created. This class runs the application. ? package com.otv.start; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; /** * @author onlinetechvision.com * @since 17 Oct 2011 * @version 1.0.0 * */ public class Application { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml"); Starter starter = (Starter) context.getBean("Starter"); starter.start(); } } STEP 11 : CREATE applicationContext.xml applicationContext.xml is created. ? STEP 12 : ALTERNATIVE METHOD TO CREATE THREAD POOL ThreadPoolTaskExecutor Class provided by Spring can also be used to create Thread Pool. ? STEP 13 : BUILD PROJECT After OTV_Spring_ThreadPool Project is build, OTV_Spring_ThreadPool-0.0.1-SNAPSHOT.jar will be created. STEP 14 : RUN PROJECT After created OTV_Spring_ThreadPool-0.0.1-SNAPSHOT.jar file is run, below output logs will be shown : ? 18.10.2011 20:08:48 DEBUG (TestRejectedExecutionHandler.java:19) - Task7 : has been rejected 18.10.2011 20:08:48 DEBUG (TestRejectedExecutionHandler.java:19) - Task8 : has been rejected 18.10.2011 20:08:48 DEBUG (TestRejectedExecutionHandler.java:19) - Task9 : has been rejected 18.10.2011 20:08:48 DEBUG (TestTask.java:25) - Task1 : is started. 18.10.2011 20:08:48 DEBUG (TestTask.java:25) - Task6 : is started. 18.10.2011 20:08:48 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 2 - CompletedTaskCount : 0 - TotalTaskCount : 5 - isTerminated : false 18.10.2011 20:08:48 DEBUG (TestTask.java:25) - Task5 : is started. 18.10.2011 20:08:53 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 0 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:08:58 DEBUG (TestTask.java:27) - Task6 : is completed. 18.10.2011 20:08:58 DEBUG (TestTask.java:27) - Task1 : is completed. 18.10.2011 20:08:58 DEBUG (TestTask.java:25) - Task3 : is started. 18.10.2011 20:08:58 DEBUG (TestTask.java:25) - Task2 : is started. 18.10.2011 20:08:58 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 2 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:08:58 DEBUG (TestTask.java:27) - Task5 : is completed. 18.10.2011 20:08:58 DEBUG (TestTask.java:25) - Task4 : is started. 18.10.2011 20:09:03 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 3 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:09:08 DEBUG (TestTask.java:27) - Task2 : is completed. 18.10.2011 20:09:08 DEBUG (TestTask.java:27) - Task3 : is completed. 18.10.2011 20:09:08 DEBUG (TestTask.java:27) - Task4 : is completed. 18.10.2011 20:09:08 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 0 - CompletedTaskCount : 6 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:09:13 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 0 - CompletedTaskCount : 6 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:09:18 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 0 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 0 - CompletedTaskCount : 6 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:09:23 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 0 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 0 - CompletedTaskCount : 6 - TotalTaskCount : 6 - isTerminated : false 18.10.2011 20:09:28 DEBUG (TestTask.java:25) - Task10 : is started. 18.10.2011 20:09:28 DEBUG (TestRejectedExecutionHandler.java:19) - Task16 : has been rejected 18.10.2011 20:09:28 DEBUG (TestRejectedExecutionHandler.java:19) - Task17 : has been rejected 18.10.2011 20:09:28 DEBUG (TestRejectedExecutionHandler.java:19) - Task18 : has been rejected 18.10.2011 20:09:28 DEBUG (TestTask.java:25) - Task14 : is started. 18.10.2011 20:09:28 DEBUG (TestTask.java:25) - Task15 : is started. 18.10.2011 20:09:28 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 6 - TotalTaskCount : 12 - isTerminated : false 18.10.2011 20:09:33 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 6 - TotalTaskCount : 12 - isTerminated : false 18.10.2011 20:09:38 DEBUG (TestTask.java:27) - Task10 : is completed. 18.10.2011 20:09:38 DEBUG (TestTask.java:25) - Task11 : is started. 18.10.2011 20:09:38 DEBUG (TestTask.java:27) - Task14 : is completed. 18.10.2011 20:09:38 DEBUG (TestTask.java:27) - Task15 : is completed. 18.10.2011 20:09:38 DEBUG (TestTask.java:25) - Task12 : is started. 18.10.2011 20:09:38 DEBUG (TestTask.java:25) - Task13 : is started. 18.10.2011 20:09:38 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 9 - TotalTaskCount : 12 - isTerminated : false 18.10.2011 20:09:43 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 3 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 3 - CompletedTaskCount : 9 - TotalTaskCount : 12 - isTerminated : false 18.10.2011 20:09:48 DEBUG (TestTask.java:27) - Task11 : is completed. 18.10.2011 20:09:48 DEBUG (TestTask.java:27) - Task13 : is completed. 18.10.2011 20:09:48 DEBUG (TestTask.java:27) - Task12 : is completed. 18.10.2011 20:09:48 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 0 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 0 - CompletedTaskCount : 12 - TotalTaskCount : 12 - isTerminated : true 18.10.2011 20:09:53 DEBUG (ThreadPoolMonitorService.java:39) - CurrentPoolSize : 0 - CorePoolSize : 1 - MaximumPoolSize : 3 - ActiveTaskCount : 0 - CompletedTaskCount : 12 - TotalTaskCount : 12 - isTerminated : true STEP 15 : DOWNLOAD OTV_Spring_ThreadPool

[This article was written by Artem Bilan.] Dear Spring community, As we promised in the Release Candidate blog post, we are pleased to announce that the Spring Integration Java DSL 1.0 GA is now available. As usual, use the Release Repository with Maven or Gradle, or download a distribution archive, to give it a spin. See the project home page for more information. First of all, we are glad to share with you that on Nov 12, 2014, DZone research recognized Spring Integration as the leader in the ESB / Integration framework space, leading with 42% marketshare, in a publication of their recent survey results. And the report is the most popular DZone Guide in November, with more than 12 000 downloads already! Don't miss it: very exciting. We hope the release of the Spring Integration Java DSL adds more excitement!. Many thanks to all contributors, including several who are new to the community. The release includes just a few bug fixes, since the release candidate, and a lot of JavaDocs! Not specifically related to the the release, I want to present here some resources on the matter. We are observing many valuable DSL questions on Stack Overflow. Josh Long's tech tip showing how we can use together Spring Boot, REST, Spring Integration 4.1 WebSocket support and Spring Integration Java DSL plus Java 8 features. The Jdbc Splitter implementation in the project tests. My gist to demonstrate how we can use Reactor Streams together with the Spring Integration Java DSL. Dave Syer has started to use Spring Integration Java DSL in the Spring Cloud Bus project. Don't miss the si4demo to see the evolution of Spring Integration including the Java DSL, as shown at the 2014 SpringOne/2GX Conference. (Video should be available soon). Especial thanks to Biju Kunjummen who has done some nice articles on DZone to introduce Spring Integration Java DSL: https://dzone.com/articles/spring-integration-java-dsl, https://dzone.com/articles/spring-integration-java-dsl-0. And of course, with the latest Spring XD, we can build Modules based on @Configuration including Spring Integration Java DSL IntegrationFlow definitions. Just after this announcement I'm going to publish a DSL Tutorial to explain concepts and features using the Java DSL version of the Cafe Demo sample as material. As always, we look forward to your comments and feedback (StackOverflow (spring-integration tag), Spring JIRA, GitHub) and we very much welcome contributions!

Compared to other features, real-time search capability is undoubtedly one of the most important features in Elasticsearch. Today we’ll look closely how is provided real-time search by Elasticsearch. Real time First of all, if we need to explain the concept of real-time, in general, we can say that the delay between input and out time in the information is small at real-time systems. This means, data is taken without data accumulation, processed in real time. Today, the best solution Elasticsearch known for real-time search, when a record is added to it for storage makes it searchable in 1 second. How? As is known, the disks are able to create a risk of bottleneck for I/O operations at the data persistence step. Also some mechanisms used for prevent any loss of data increases cost of time. At this point Elasticsearch uses the file-system cache that sitting between itself and the disk for overcome the risk of bottleneck and ensure the a new document can be searched in real time. A new segment is written to the file-system cache first and only later it flushed to disk by Elasticsearch. This lightweight process of writing and opening a new segment is called a refresh in Elasticsearch. By default, all shards is refreshed automatically once every second. In this way, Elasticsearch support real-time search. Test time Above digression about the time of refresh of the shards you can bring to mind the following questions: What happens, when a new document is requested in less than 1 second time? Can be documents requested, without having to depend of the refresh period shards of managed by Elasticsearch? Short answers. Elasticsearch does not return the document. Yes. Now let’s get clarity on this issue is a simple example. hakdogan$ curl -XPUT localhost:9200/kodcucom/document/1 -d'{ > "title": "Document A" > }' We sent a document to Elasticsearch. The index name is kodcucom, type document, id value 1. The title field is only field in the document and the value of "Document A". Let’s take this document from Elasticsearch. hakdogan$ curl -XGET localhost:9200/kodcucom/document/1?pretty { "_index" : "kodcucom", "_type" : "document", "_id" : "1", "_version" : 1, "found" : true, "_source":{ "title": "Document A" } } As expected, the document was returned to us. Well, if we keep short the time between document recording and get request than default shard refresh time what will happen? Let’s see. hakdogan$ curl -XPUT localhost:9200/kodcucom/document/2 -d'{"title": "Document B"}'; curl -XGET localhost:9200/kodcucom/_search?pretty {"_index":"kodcucom","_type":"document","_id":"2","_version":1,"created":true}{ "took" : 38, "timed_out" : false, "_shards" : { "total" : 5, "successful" : 5, "failed" : 0 }, "hits" : { "total" : 1, "max_score" : 1.0, "hits" : [ { "_index" : "kodcucom", "_type" : "document", "_id" : "1", "_score" : 1.0, "_source":{ "title": "Document A" } } ] } } As can be seen, only the previous document was returned to us by Elasticsearch when we do concurrently create and get request. Well, how can I get the document concurrently? Let’s see. hakdogan$ curl -XPUT localhost:9200/kodcucom/document/3 -d'{"title": "Document C"}'; curl -XGET localhost:9200/kodcucom/_refresh; curl -XGET localhost:9200/kodcucom/_search?pretty {"_index":"kodcucom","_type":"document","_id":"3","_version":1,"created":true}{"_shards":{"total":10,"successful":5,"failed":0}{ "took" : 3, "timed_out" : false, "_shards" : { "total" : 5, "successful" : 5, "failed" : 0 }, "hits" : { "total" : 3, "max_score" : 1.0, "hits" : [ { "_index" : "kodcucom", "_type" : "document", "_id" : "1", "_score" : 1.0, "_source":{ "title": "Document A" } }, { "_index" : "kodcucom", "_type" : "document", "_id" : "2", "_score" : 1.0, "_source":{"title": "Document B"} }, { "_index" : "kodcucom", "_type" : "document", "_id" : "3", "_score" : 1.0, "_source":{"title": "Document C"} } ] } } In this command, we perform to refresh operation on kodcucom index before the search request. In this way, the document was returned to us. Auto refresh time can be changed. By setting the index.refresh_interval parameter in the configuration file. Applies to all indices in the cluster. A per-index basis by updated index setting. In addition to these, you can turn off automatic refresh. An important point to keep in mind about the refresh time of the shards, the refresh operation is costly in terms of system resources. If you wished to make changes to the auto-refresh time, this situation should be taken into account. Extension of the automatic refresh time, enables faster indexing but new documents and changes made to the existing documents will not appear in searches during specified period of time.

Spring-session is a very cool new project that aims to provide a simpler way of managing sessions in Java based web applications. One of the features that I explored with spring-session recently was the way it supports externalizing session state without needing to fiddle with the internals of specific web containers like Tomcat or Jetty. To test spring-session I have used a shopping cart type application(available here) which makes heavy use of session by keeping the items added to the cart as a session attribute, as can be seen from these screenshots: Consider first a scenario without Spring session. So this is how I have exposed my application: I am using nginx to load balance across two instances of this application. This set-up is very easy to run using Spring boot, I brought up two instances of the app up using two different server ports, this way: mvn spring-boot:run -Dserver.port=8080 mvn spring-boot:run -Dserver.port=8082 and this is my nginx.conf to load balance across these two instances: events { worker_connections 1024; } http { upstream sessionApp { server localhost:8080; server localhost:8082; } server { listen 80; location / { proxy_pass http://sessionApp; } } } I display the port number of the application in the footer just to show which instance is handling the request. If I were to do nothing to move the state of the session out the application then the behavior of the application would be erratic as the session established on one instance of the application would not be recognized by the other instance - specifically if Tomcat receives a session id it does not recognize then the behavior is to create a new session. Introducing Spring session into the application There are container specific ways to introduce a external session stores - One example is here, where Redis is configured as a store for Tomcat. PivotalGemfire provides a module to externalize Tomcat's session state. The advantage of using Spring-session is that there is no dependence on the container at all - maintaining session state becomes an application concern. The instructions on configuring an application to use Spring session is detailed very well at the Spring-session site, just to quickly summarize how I have configured my Spring Boot application, these are first the dependencies that I have pulled in: org.springframework.session spring-session 1.0.0.BUILD-SNAPSHOT org.springframework.session spring-session-data-redis 1.0.0.BUILD-SNAPSHOT org.springframework.data spring-data-redis 1.4.1.RELEASE redis.clients jedis 2.4.1 and my configuration to use Spring-session for session support, note the Spring Boot specific FilterRegistrationBean which is used to register the session repository filter: import org.springframework.boot.context.embedded.FilterRegistrationBean; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.core.annotation.Order; import org.springframework.data.redis.connection.jedis.JedisConnectionFactory; import org.springframework.session.data.redis.config.annotation.web.http.EnableRedisHttpSession; import org.springframework.session.web.http.SessionRepositoryFilter; import org.springframework.web.filter.DelegatingFilterProxy; import java.util.Arrays; @Configuration @EnableRedisHttpSession public class SessionRepositoryConfig { @Bean @Order(value = 0) public FilterRegistrationBean sessionRepositoryFilterRegistration(SessionRepositoryFilter springSessionRepositoryFilter) { FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean(); filterRegistrationBean.setFilter(new DelegatingFilterProxy(springSessionRepositoryFilter)); filterRegistrationBean.setUrlPatterns(Arrays.asList("/*")); return filterRegistrationBean; } @Bean public JedisConnectionFactory connectionFactory() { return new JedisConnectionFactory(); } } And that is it! magically now all session is handled by Spring-session, and neatly externalized to Redis. If I were to retry my previous configuration of using nginx to load balance two different Spring-Boot applications using the common Redis store, the application just works irrespective of the instance handling the request. I look forward to further enhancements to this excellent new project. The sample application which makes use of Spring-session is available here: https://github.com/bijukunjummen/shopping-cart-cf-app.git

Suppose you have the following spring set-up component scan enabled a class (MailServer) with some constructors (no no-args constructor) annotated with @Component (or @Service / @Named) declaration of above class in the spring-config (Even though you have component-scan enabled, suppose you need to configure the default mail server with a name "defaultMailServer" ) injecting the above "defaultMailServer" to a property of another class (i.e. MailSender) Spring Configuration MailServer.java @Component public class MailServer { private String host; private int port; private String protocol; public MailServer(final String host, final int port, final String protocol) { this.host = host; this.port = port; this.protocol = protocol; } //getters } MailSender.java @Service public class MailSenderImpl implements MailSender { @Autowired @Qualifier("defaultMailServer") private MailServer mailServer; @Override public void send() { // TODO } } Main.java public class Main { private static final String CONFIG_PATH = "classpath*:application-config.xml"; public static void main(final String[] args) { final ApplicationContext context = new ClassPathXmlApplicationContext(CONFIG_PATH); final MailSender mailSender = context.getBean(MailSenderImpl.class); mailSender.send(); } } Nothing looks wrong. But when you execute the program you will get the following exception. org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [me.fahimfarook.mail.MailServer]: No default constructor found; This error message is misleading because we are not accessing MailServer with default constructor anywhere in our code. We have injected "defaultMailServer" which is properly defined with constructor-args. However, if you add a no-args constructor to MailServer this exception will go away. That means spring context is trying to create a MailServer object using no-args constructor somewhere even though we have defined a MailServer with constructor-args. But we have defined a MailServer bean with constructor-args and accessing that bean only? The reason for that is - we have defined a bean explicitly in the spring config xml while we have enabled component scanning. Spring will create the "defaultMailServer" bean successfully since constructor-args have been defined in the spring config xml. However, since component scanning has been enabled, spring will try to automatically discover and register another MailServer bean. However, this will fail because spring can't create an object using the defined constructor as we have not auto-wired the constructor / parameters in the constructor. As the second step, spring will try to create a MailServer with no-args constructor. Therefore you need to have auto-wired the constructor which you defined in the spring-config file in order to get rid of this error. MailServer.java - Fixed @Component public class MailServer { private String host; private int port; private String protocol; @Autowired public MailServer(@Value("")final String host, @Value("#{new Integer(-1)}")final int port, @Value("")final String protocol) { this.host = host; this.port = port; this.protocol = protocol; } } Now that you have auto-wired the constructor which is defined with "defaultMailServer", spring can create this bean and it will not demand a default constructor. However, if spring had thrown BeanInstantiationException with a message like "Constructor for defaultMailServer could not be found" instead of "No default constructor found", the exact issue with the code could have been identified easily. In summary: If component scanning is enabled, spring will try to create a bean even though a bean of that class has already been defined in the spring config xml. However if the bean defined in the spring config file and the auto-discovered bean have the same name, spring will not to create a new bean while it does component scanning. If a bean does not have a no-args constructor, at-least one of the constructors must be auto-wired. If no constructor is auto-wired, spring will try to create an object using default no-args constructor. Original post here

In Spring, a bean is instantiated before its properties are injected. That is: Instantiate the bean first Inject the properties This is because spring uses setter methods of the instantiated bean in order to inject properties. (This is true if the property injection is declared in the spring configuration file, however if the bean properties are auto-wired - no setter methods are required. But still spring instantiates the bean first before auto-wiring properties.) Therefore you cannot access the properties from your constructor (unless properties are injected through constructor-args) as the properties are still holding null/ default values when accessed within the constructor. Consider the following example. Spring configuration file Engine.java package me.fahimfarook.sample.spring; import java.util.logging.Logger; public class Engine { private String make; private int cylinders; private static Logger LOGGER = Logger.getLogger(Engine.class.getName()); public void cleanup() { LOGGER.info("Engine::cleanup - cleaning-up engine."); } public String getMake() { return make; } public void setMake(final String make) { this.make = make; } public int getCylinders() { return cylinders; } public void setCylinders(final int cylinders) { this.cylinders = cylinders; } } Car.java package me.fahimfarook.sample.spring; public class Car { private String brand; private int year; private Engine engine; public Car() { this.engine.cleanup(); } public String getBrand() { return brand; } public void setBrand(final String brand) { this.brand = brand; } public int getYear() { return year; } public void setYear(final int year) { this.year = year; } public Engine getEngine() { return engine; } public void setEngine(final Engine engine) { this.engine = engine; } } As you can see I'm calling engine.start() from the constructor of the Car. Main.java package me.fahimfarook.sample.spring; import org.springframework.context.ApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Main { private static final String CONFIG_PATH = "classpath*:configs/spring/applicaton-config.xml"; public static void main(String[] args) { final ApplicationContext context = new ClassPathXmlApplicationContext(CONFIG_PATH); final Car car = (Car)context.getBean("car"); } } When you execute this main method you will get a NullPointerException. Caused by: java.lang.NullPointerException at me.fahimfarook.sample.spring.Car.start(Car.java:18) at me.fahimfarook.sample.spring.Car.(Car.java:14) Even though we have configured spring to inject engine into car, by the time of instantiation (of car bean), spring has not injected the engine. We have two workarounds to solve this problem. 1. From a design perspective this NullPointerException indicates a code smell. That is the relationship between the car and engine should be "composition" rather than "aggregation". The engine must cease to exist when car is destroyed. Also, the engine cannot exist without a car. In order to enforce composition between car and engine we need the following 2 changes. Add a constructor to Car with an Engine parameter Remove the setEngine() mutator Here's the fixed code. Spring config - Fixed Note that engine is injected via a constructor-arg and is removed. Car.java - Fixed package me.fahimfarook.sample.spring; public class Car { private String brand; private int year; private Engine engine; public Car(final Engine engine) { this.engine = engine; this.engine.start(); } public String getBrand() { return brand; } public void setBrand(final String brand) { this.brand = brand; } public int getYear() { return year; } public void setYear(final int year) { this.year = year; } public Engine getEngine() { return engine; } // public void setEngine(final Engine engine) { // this.engine = engine; // } } Note that the setter of engine has been commented out and and Car is having a constructor with an Engine parameter. Now if you execute the main method you will not get the NullPointerException anymore as we have forced spring to inject an engine while construction of the car. 2. The other workaround would be to move the logic in the constructor to a separate method and annotate that method with @PostConstruct annotation. @PostConstruct is a standard Java annotation which is supported by spring. @PostConstruct indicates that the method annotated with @PostConstruct must be invoked once all its dependencies are injected only. However in our example you need to have enabled in order to support annotations. You can find more information about this annotation here.

This article represents code samples along with related concepts for two different ways in which an Angular app can be defined.