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Refcard #198

Java Enterprise Edition 7

Streamlining Modern Java Development

Written by

Andrew Rubinger Senior Software Engineer, JBoss, a Division of Red Hat, Inc.
Arun Gupta VP, Developer Relations, Couchbase
Lincoln Baxter Chief Editor, Red Hat

Java Enterprise Edition allows programmers to write less and focus on delivering clean business logic. This newly updated Refcard covers the key APIs of Java EE 7 that are the most relevant to modern development - such as WebSocket, JSON Processing, Concurrency Utilities, and JAX-RS.

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Section 1

About the Platform

Enterprise software development is inherently complex; multi-user systems open the door to concerns such as transactional integrity, security, persistence integration, and interaction between components. Very simply put, the mission of the Java Enterprise Edition is to enable an out-of-the-box set of configurable services and functionality, which allow the programmer to write less and focus on delivering clean business logic.

Java EE 7 is in fact an aggregate of many interoperable technologies designed to deliver a unified experience. Application Servers which are certified to the standards defined by the Java Community Process are intended to service applications written to the specifications within the platform.

For the sake of brevity, this reference will focus on the key APIs of Java EE 7 most relevant to modern development.

Section 2

Java Platform, Enterprise Edition 7 (Java EE 7)

JSR-342

This umbrella specification ties together the various subsystems that comprise the platform, and provides additional integration support where necessary. The Java EE 7 platform added the following new subsystems:

  • Java API for WebSocket 1.0
  • Batch Applications for the Java Platform 1.0
  • Java API for JSON Processing 1.0
  • Concurrency Utilities for Java EE 1.0

In addition, Java API for RESTful Web Services 2.0 and Java Message Service 2.0 went through significant updates. Several other technologies were updated to provide improved productivity and features:

  • Contexts and Dependency Injection 1.1
  • Bean Validation 1.1
  • Servlet 3.1
  • Java Persistence API 2.1
  • Java Server Faces 2.2
  • Java Transaction API 1.2

There are many useful resources for Java EE 7 available online, both on Oracle’s website and in the Java EE 7 community samples GitHub repository:

Section 3

Java API for WebSocket 1.0

JSR-356

WebSocket provides a full-duplex, bi-directional communication over a single TCP channel. This overcomes a basic limitation of HTTP where a server can send updates to the client and a TCP connection is maintained between client and server until one of them explicitly closes it. WebSocket is also a very lean protocol and requires minimal framing on the wire. Java API for WebSocket 1.0 is a new addition to the platform and provides an annotated and programmatic way to develop, deploy, and invoke WebSocket endpoints.

Annotated server endpoints can be defined as:

@ServerEndpoint(value="/chat", encoders=ChatMessageEncoder.class, decoders=ChatMessageDecoder.class)
public class ChatServer {
    @OnMessage
    public String receiveMessage(ChatMessage message, Session client) {
       for (Session s : client.getOpenSessions()) {
           s.getBasicRemote().sendText(message);
       }
    }
}

Client endpoints are defined with @ClientEndpoint and can be connected to a server endpoint via:

WebSocketContainer container = ContainerProvider.getWebSocketContainer();
String uri = "ws://localhost:8080/chat/websocket";
container.connectToServer(ChatClient.class, URI.create(uri));

Alternatively, programmatic server endpoints can be defined as:

public class ChatServer extends Endpoint {
    @Override
    public void onOpen(Session session, EndpointConfig ec) {
        session.addMessageHandler(...);
    }
}

Programmatic endpoints must also be registered in a ServerApplicationConfig to assign their external URL:

@Override
public class MyServerApplicationConfig implements ServerApplicationConfig {
    @Override
    public Set<ServerEndpointConfig> getEndpointConfigs(Set<Class<? extends Endpoint>> set) {
        return new HashSet<ServerEndpointConfig>() {
            {
                add(ServerEndpointConfig.Builder.create(ChatServer.class, "/chat").build());
            }
        };
    }
}

Public API from javax.websocket:

Class Name Description
@ServerEndpoint Annotation that decorates a POJO as a WebSocket server endpoint
@ClientEndpoint Annotation that decorates a POJO as a WebSocket client endpoint
@PathParam Annotation that assigns parameters of an endpoint URI-template
Session Represents a conversation between two WebSocket endpoints
Encoders Interface to convert application objects into WebSocket messages
Decoders Interface to convert WebSocket objects into application messages
MessageHandler Interface to receive incoming messages in a conversation
@OnMessage Annotation to make a Java method receive incoming message
@OnOpen Decorates a Java method to be called when connection is opened
@OnClose Decorates a Java method to be called when connection is closed
@OnError Decorates a Java method to be called when there is an error
Section 4

Batch Applications for the Java Platform 1.0

JSR-352

Batch Applications allows developers to easily define non-interactive, bulk-oriented, long-running tasks in item-oriented and task-oriented ways. It provides a programming model for batch applications and a runtime for scheduling and executing batch jobs. It supports item-oriented processing using Chunks and task-oriented processing using Batchlets. Each job is defined using Job Specification Language, aka “Job XML”, that must be created in the META-INF/batch-jobs/ folder (subdirectories of this folder are ignored).

Example `META-INF/batch-jobs/my-job.xml` file:

<job id="myJob" xmlns="http://xmlns.jcp.org/xml/ns/javaee" version="1.0">
    <step id="myStep">

        <chunk item-count="3">

            <reader ref="myItemReader"/>
            <processor ref="myItemProcessor"/>
            <writer ref="myItemWriter"/>

        </chunk> 

Each item is read, processed, and aggregated for writing. item-count number of items are processed within a container-managed transaction.

Different elements define the sequence of a job:

  • Step: Independent and sequential phase of a job
  • Flow: Sequence of execution elements that execute together as a unit
  • Split: Set of flows that execute concurrently
  • Decision: Customized way of determining sequencing among step, flows, and splits

Public API from javax.websocket:

Class Name Description
BatchRuntime Represents the JSR 352 runtime
JobOperator Interface for operating on batch jobs
ItemReader Batch artifact that reads item for chunk processing
ItemProcessor Batch artifact that operates on an input item and produces an output item for chunk processing
ItemWriter Batch artifact that writes to a list of item for chunk processing
Batchlet Batch step for item-oriented processing
@BatchProperty Annotation to define a batch property injected from Job XML
JobListener Interface that intercepts job execution
StepListener Interface that intercepts step execution
ChunkListener Interface that intercepts chunk processing
CheckpointAlgorithm Provides a custom checkpoint policy for chunk steps
PartitionMapper Provide unique batch properties for each batch execution
PartitionReducer Unit of work demarcation across partitions
Section 5

Java API for JSON Processing 1.0

JSR-353

JSON is a lightweight data-interchange format and is the common format of the web for consuming and creating web services data. A new API to parse and generate JSON is included in the platform, which reduces the dependency on third-party libraries. The API offers to produce/consume JSON text in a low-level streaming fashion (similar to StAX API for XML).

JsonParser parser = Json.createParser(new FileInputStream(...));

The event-based parser allows an application developer to ask for an event using parser.next(). This API returns a JsonParser.Event which consists of values that indicate the start of an object, end of an object, and other similar events. This gives more procedural control over processing the JSON.

The streaming API allows developers to generate a simple JSON object as:

StringWriter w = new StringWriter();
JsonGenerator gen = factory.createGenerator(w);
gen
    .writeStartObject()
    .write("apple", "red")
    .write("banana", "yellow")
    .writeEnd();

The API also offers a high-level Object Model API that provides immutable object models for JSON object and array structures. These JSON structures are represented as object models via the Java types JsonObject and JsonArray.

JsonReader reader = Json.createReader(new FileInputStream(...));
JsonObject json = reader.readObject();

The Object Model API allows developers to generate a simple JSON object as:

Json.createObjectBuilder()
      .add("apple", "red")
      .add("banana", "yellow")
.build();

Public API from javax.json:

Json Factory class for creating JSON processing objects.
JsonObject Represents an immutable JSON object value
JsonArray Represents an immutable JSON array
JsonWriter Writes a JSON object or array structure to an output source
JsonReader Reads a JSON object or array structure from an input source.
JsonGenerator Writes JSON data to an output source in a streaming way.
JsonParser Provides forward, read-only access to JSON data in a streaming way.
JsonParser.EVENT An event from JsonParser
Section 6

Concurrency Utilities for Java EE 1.0

JSR-236

Concurrency Utilities for Java EE provides a simple, standardized API for using concurrent programming techniques from application components without compromising container integrity, while still preserving the Java EE platform’s fundamental benefits. This API extends the Concurrency Utilities API developed under JSR-166 and found in Java 2 Platform, Standard Edition 7 in the java.util.concurrent package.

Four managed objects are provided:

ManagedExecutorService
ManagedScheduledExecutorService
ManagedThreadFactory
ContextService

A new default instance of these objects is available for injection in the following JNDI namespace:

java:comp/DefaultManagedExecutorService.
java:comp/DefaultManagedScheduledExecutorService
java:comp/DefaultManagedThreadFactory
java:comp/DefaultContextService

A new instance of ManagedExecutorService can be created as:

InitialContext ctx = new InitialContext(); 
ManagedExecutorService executor = (ManagedExecutorService)ctx.lookup("java:comp/DefaultManagedExecutorService");

It can also be injected as:

@Resource(lookup="java:comp/DefaultManagedExecutorService")
ManagedExecutorService executor;

An ExecutorService obtained via any of these methods can then be used as expected:

executor.invokeAll(...);
executor.shutdown();

An application-specific ManagedExecutor can be created by adding the following fragment to web.xml:

<resource-env-ref>
    <resource-env-ref-name>
        concurrent/myExecutor
    </resource-env-ref-name>
    <resource-env-ref-type>
        javax.enterprise.concurrent.ManagedExecutorService
    </resource-env-ref-type>
</resource-env-ref>

Public API from javax.enterprise.concurrent

ManagedExecutorService Manageable version of ExecutorService
ManagedScheduledExecutorService Manageable version of ScheduledExecutorService
ManagedThreadFactory Manageable version of ThreadFactory
ContextService Provides methods for creating dynamic proxy objects with contexts in a typical Java EE application
ManagedTaskListener Used to monitor the state of a task’s Future
Section 7

Java API for RESTful Web Services (JAX-RS) 2.0

JSR-339

JAX-RS provides a standard annotation-driven API that helps developers build a RESTful web service and invoke it. The standard principles of REST, such as—identifying a resource via URI; defining a set of methods to access the resource; and allowing for multiple representation formats of a resource—can be easily marked in a POJO via annotations.

JAX-RS 2 adds a Client API that can be used to access web resources. The API provides support for standard HTTP verbs, custom media types by integration with entity providers, and dynamic invocation:

Author author = ClientBuilder
    .newClient()
    .target("http://localhost:8080/resources/authors")
    .path("{author}")
    .resolveTemplate("author", 1)
    .request
    .get(Author.class);

The Client API also permits retrieval of the response asynchronously by adding an async() method call before the method invocation.

Author author = ClientBuilder.newClient().target(…).async().get(Author.class);

JAX-RS enables the creation of server-side endpoints using annotations. To enable JAX-RS, create a class that extends Application and specify the root server endpoint URL using the @ApplicationPath annotation:

@ApplicationPath("/webapi")
public class MyApplication extends Application {
}

JAX-RS 2 introduces asynchronous endpoints that may be defined to suspend the client connection if the response is not readily available and later resume when it is. Here, an Executor is used to perform work in a separate thread:

@Path("authors")
public class AuthorEndpoint {
    @GET
    public void getAll(@Suspended final AsyncResponse ar) {
        executor.submit(new Runnable() {
            public void run() {
               ar.resume(authorsDatabase.getAll());
            }
        ));
    }
}

A synchronous endpoint that uses @PathParam to identify a single book. Note that this endpoint’s @Path will be combined with the @ApplicationPath; this results in a complete endpoint path of “/webapi/books/{id}”:

@Path("books/{id}")
public class BookEndpoint {
    @GET
    public Book get(@PathParam("id") final int bookId) {
       return booksDatabase.get(bookId);
    }
}

Filters and Entity Interceptors are extension points that customize the request/response processing on the client and the server side. Filters are mainly used to modify or process incoming and outgoing request or response headers. A filter is defined by implementing ClientRequestFilter, ClientResponseFilter, ContainerRequestFilter, and/or ContainerResponseFilter.

public class HeaderLoggingFilter implements ClientRequestFilter, ClientResponseFilter {
    // from ClientRequestFilter
    public void filter(ClientRequestContext crc) throws IOException {
        for (Entry e : crc.getHeaders().entrySet()) {
             &hellip; = e.getKey();
             &hellip; = e.getValue();
        }
    }

    // from ClientResponseFilter
    public void filter(ClientRequestContext crc, ClientResponseContext crc1) throws IOException {
        ...
    }
}

Entity Interceptors are mainly concerned with marshaling and unmarshaling of HTTP message bodies. An interceptor is defined by implementing ReaderInterceptor or WriterInterceptor, or both.

public class BodyLoggingFilter implements WriterInterceptor {
    public void aroundWriteTo(WriterInterceptorContext wic) {
        wic.setOutputStream(...);
        wic.proceed();
    }
}

JAX-RS 2 also enables declarative validation of resources using Bean Validation 1.1. In addition to validating any @PathParam or @QueryParam method parameters, validation constraints may also be placed on the JAX-RS resource class fields:

@Path("/names")
public class Author {
    @NotNull @Size(min=5)
    private String firstName;
    ...
}

Public API selection from javax.ws.rs package:

Class Name Description
AsyncInvoker Uniform interface for asynchronous invocation of HTTP methods
ClientBuilder Entry point to the Client API
Client Entry point to build and execute client requests
ClientRequestFilter Interface implemented by client request filters
ClientResponseFilter Interface implemented by client response filters
ContainerRequestFilter Interface implemented by server request filters
ContainerResponseFilter Interface implemented by server response filters
ConstrainedTo Indicates the runtime context in which a JAX-RS provider is applicable
Link Class representing hypermedia links
ReaderInterceptor Interface for message body reader interceptor
WriterInterceptor Interface for message body writer interceptor
NameBinding Meta-annotation used for name binding annotations for filters and interceptors
WebTarget Resource target identified by a URI
Section 8

Java Message Service 2.0

JSR-343

Message-oriented middleware (MOM) allows sending and receiving messages between distributed systems. JMS is an MOM that provides a way for Java programs to create, send, receive, and read an enterprise system’s messages.

A message can be easily sent as the following example:

@Stateless
@JMSDestinationDefinition(name="...", interfaceName="javax.jms.Queue")
public class MessageSender {
    @Inject 
    JMSContext context;
    @Resource(mappedName=...)
    Destination myQueue;
    public void sendMessage() {
        context.sendProducer().send(myQueue, message);
    }
}

The newly introduced, simplified API is very fluent, uses runtime exceptions, is annotation-driven, and makes use of CDI to reduce the boilerplate code.

A message can be received as:

public void receiveMessage() {
    String message = context.createConsumer(myQueue).receiveBody(String.class, 1000);
}

JMS 2.0 queues and topics may now be configured at deployment time using the @JMSDestinationDefinitions annotation. Queues may be injected using the @Resource annotation:

@JMSDestinationDefinitions(
    value = {
        @JMSDestinationDefinition(name = "java:/queue/my-queue",
            interfaceName = "javax.jms.Queue", destinationName = "my-queue"),
        @JMSDestinationDefinition(name = "java:/topic/my-topic",
            interfaceName = "javax.jms.Topic", destinationName = "my-topic")
        }
)

@Stateless
public class MessageSender {
    @Resource(lookup = "java:/queue/my-queue")
    private Queue queue;    
}

Public API from javax.jms:

JMSContext Main interface to the simplified API
JMSProducer Simple object used to send messages on behalf of JMSContext
JMSConsumer Simple object used to receive messages from a queue or topic
JMSConnectionFactory Annotation used to specify the JNDI lookup name of ConnectionFactory
JMSDestinationDefinition Annotation used to specify dependency on a JMS destination
QueueBrowser Object to look at messages in client queue without removing them
Section 9

Contexts and Dependency Injection for Java (CDI 1.1)

JSR-346

The Java Contexts and Dependency Injection specification (CDI) introduces a standard set of application component management services to the Java EE platform. CDI manages the lifecycle and interactions of stateful components bound to well-defined contexts. CDI provides typesafe dependency injection between components and defines: interceptors and decorators to extend the behavior of components; an event model for loosely coupled components; and an SPI allowing portable extensions to integrate cleanly with the Java EE environment.

The Java EE 7 platform, by default, enables CDI injection for all Java classes that explicitly contain a CDI scope or EJB annotation. The following are examples of beans that would be automatically enabled for injection using default settings.

@Dependent // CDI scope annotation
public class ExampleBean {
}

@Stateful // EJB annotation
public class ExampleBean {
}

To configure non-default bean discovery settings, a new “bean-discovery-mode” attribute is added to beans.xml (located in /WEB-INF/beans.xml in web applications, and /META-INF/beans.xml in JAR libraries):

<beans
    xmlns=“http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation=“http://xmlns.jcp.org/xml/ns/javaee
    http://xmlns.jcp.org/xml/ns/javaee/beans\_1\_1.xsd” bean-discovery-mode=“all”>

</beans>

This attribute can take the following values:

  • all: All types in the archive are considered for injection.

  • annotated: (default) Only types with an explicitly declared CDI scope are considered for injection.

  • none: Disable CDI

By default, CDI interceptors are disabled. They can be enabled and ordered via the @javax.interceptor.Interceptor.Priority annotation as shown (the same can be done for decorators and alternatives):

@Priority(Interceptor.Priority.APPLICATION+10)
@Interceptor
@Logging
public class LoggingInterceptor {
    //. . .
}

In addition, CDI 1.1 also introduces the following features:

  • Support for @AroundConstruct lifecycle callback for constructors
  • Binding interceptors to constructors
  • Interceptor binding moved to the interceptors spec, allowing for reuse by other specifications
  • Support for decorators on built in beans
  • EventMetadata to allow inspection of event metadata
  • @Vetoed annotation allowing easy programmatic disablement of classes
  • Many improvements for passivation capable beans, including @TransientReference allowing instances to be retained only for use within the invoked method or constructor
  • Scope activation and destruction callback events
  • AlterableContext allowing bean instances to be explicitly destroyed
  • Class exclusion filters to beans.xml to prevent scanning of classes and packages
  • Unmanaged allowing easy access to non-contextual instances of beans
  • Allow easy access to the current CDI container
  • AfterTypeDiscovery event, allowing extensions to register additional types after type discovery
  • @WithAnnotations as a way of improving extension loading performance
Section 10

Bean Validation 1.1

JSR-349

Expanded in Java EE 7, the Bean Validation Specification provides for unified declaration of validation constraints upon bean data. It may be used to maintain the integrity of an object at all levels of an application: from user form input in the presentation tier (JSF) all the way to the persistence layer (JPA).

New in the 1.1 release is:

  • Method-level validation (validation of parameters or return values)
  • Dependency injection for Bean Validation components
  • Group conversion in object graphs
  • Error message interpolation using EL expressions
  • Support for method and constructor validation (via CDI, JAX-RS, etc.)
  • Integration with CDI (Validator and ValidatorFactory injectable instances, ConstraintValidator instances being CDI beans and thus accept @Inject, etc.)

Here we show how we may apply Bean Validation constraints in a declarative fashion to ensure the integrity of a User object.

public class User {
    @NotNull
    @Size(min=1, max=15)
    private String firstname;

    @NotNull
    @Size(min=1, max=30)
    private String lastname;

    @Pattern(regexp="\b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b")
    public String email;
}

Custom constraints can be created to provide reusable annotations with specific validation definitions:

@Pattern(regexp = "[a-zA-Z0-9-]+")
@Constraint(validatedBy = {})
@Target({ METHOD, FIELD, ANNOTATION_TYPE })
@Retention(RUNTIME)
public @interface Username {
    String message() default "Invalid username: must only contain letters";
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

To enable internationalization and localization, custom constraint messages may reference resource bundle properties:

String message() default “{validation.invalid_username}”;

Custom constraints may also use custom ConstraintValidators. This is specified using the validatedBy attribute:

@Constraint(validatedBy = UsernameValidator.class)
Section 11

Java Servlet 3.1

JSR-340

Servlet technology models the request/response programming model, and is commonly used to extend HTTP servers to tie into server-side business logic. In Servlet 3.1, the specification has been expanded over previous versions to include support for non-blocking I/O, security, and API enhancements.

To register a servlet in Java EE 7, annotate an implementation of HttpServlet with @WebServlet (the web descriptor WEB-INF/web.xml is no longer required):

@WebServlet("/report")
public class MoodServlet extends HttpServlet {
   ...
}
Section 12

Non-Blocking I/O

Servlet 3.1 introduces a non-blocking I/O (NIO) API, which can be used to read input as it becomes available from the request via a ReadListener:

AsyncContext context = request.startAsync();
ServletInputStream input = request.getInputStream();
input.setReadListener(new ReadListener(){...});

The ReadListener interface defines three callbacks:

  • onAllDataRead() Invoked when all data for the current request has been read.
  • onDataAvailable() When an instance of the ReadListener is registered with a ServletInputStream, this method will be invoked by the container the first time it is possible to read data.
  • onError(Throwable t) Invoked when an error occurs processing the request.

Security enhancements

  • Applying run-as security roles to #init and #destroy methods
  • Added HttpSessionIdListener to enable detection of session fixation attacks, and enabled deterrence of session fixation attacks by enabling changing the session ID via HttpServletRequest.changeSessionId()
  • Addition of <deny-uncovered-http-methods/> to web.xml in order to block HTTP methods not covered by an explicit constraint

Miscellaneous Additions to the API

  • ServletResponse.reset() clears any data that exists in the buffer as well as the status code, headers. In addition, Servlet 3.1 also clears the state of getServletOutputStream() and getWriter().
  • ServletResponse.setCharacterEncoding(…) sets the character encoding (MIME charset) of the response being sent to the client, for example, to UTF-8.
  • Relative protocol URL can be specified in HttpServletResponse.sendRedirect. This will allow a URL to be specified without a scheme. That means instead of specifying “http://anotherhost.com/foo/bar.jsp” as a redirect address, “//anotherhost.com/foo/bar.jsp” can be specified. In this case the scheme of the corresponding request will be used.
Section 13

Java Persistence 2.1

JSR-338

Most enterprise applications will need to deal with persistent data, and interaction with relational databases can be a tedious and difficult endeavor. The Java Persistence API (JPA) specification aims to provide an object view of backend storage in a transactionally-aware manner. By dealing with POJOs, JPA enables developers to perform CRUD operations without the need for manually tuning SQL.

To activate JPA, a META-INF/persistence.xml file must be present in the JAR or WAR in which persistence functionality is to be used; however, a default data-source is now provided, simplifying testing and development.

Example META-INF/persistence.xml:

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"  xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence 
        http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="MyPU" transaction-type="JTA"></persistence-unit>
</persistence>

New in JPA 2.1 is:

Support for Stored Procedures

We may use the new @NamedStoredProcedureQuery annotation atop an entity to define a stored procedure:

@Entity
@NamedStoredProcedureQuery(name="newestBlogsSP", procedureName="newestBlogs")
public class Blog {...}

From the client side, we may call this stored procedure like:

StoredProcedureQuery query = EntityManager.createNamedStoredProcedureQuery("newestBlogsSP");
query.registerStoredProcedureParameter(1, String.class, ParameterMode.INOUT);
query.setParameter(1, "newest");
query.registerStoredProcedureParameter(2, Integer.class, ParameterMode.IN);
query.setParameter(2, 10);
query.execute();
String response = query.getOutputParameterValue(1);

Bulk Update and Delete via the Query API

CriteriaUpdate, CriteriaDelete, and CommonAbstractQuery interfaces have been added to the API, and the AbstractQuery interface has been refactored.

A spec example of a bulk update may look like:

CriteriaUpdate<Customer> q = cb.createCriteriaUpdate(Customer.class); 
Root<Customer> c = q.from(Customer.class); 
q.set(c.get(Customer_.status), "outstanding")
 .where(cb.lt(c.get(Customer_.balance), 10000));

Entity listeners using CDI

Listeners on existing entity events @PrePersist, @PostPersist, @PreUpdate, and @PreRemove now support CDI injections, and entity listeners may themselves be annotated with @PostConstruct and @PreDestroy.

Synchronization of persistence contexts

In JPA 2, the persistence context is synchronized with the underlying resource manager. Any updates made to the persistence context are propagated to the resource manager. JPA 2.1 introduces the concept of unsynchronized persistence context. Here is how you can create a container-managed unsynchronized persistence context:

@PersistenceContext(synchronization=SynchronizationType.UNSYNCHRONIZED) EntityManager em;
Section 14

Java Server Faces 2.2

JSR-344

JavaServer Faces (JSF) is a user interface (UI) framework for the development of Java web applications. Its primary function is to provide a component-based toolset for easily displaying dynamic data to the user. It also integrates a rich set of patterns to help manage state and promote code reuse.

JSF 2.2 is activated automatically when any JSF *.xhtml file (referred to as a view) is detected in either the web-root directory, or the WEB-INF/resources/ directory. View files may be placed in subdirectories.

Example /catalog/item.xhtml page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
      "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:h="http://java.sun.com/jsf/html">
    <f:metadata>
        <f:viewParam id="id" name="item" value="#{catalog.itemId}"/>
        <f:viewAction action="#{catalog.loadItem}"/>
    </f:metadata>
    <h:head>
        <title>Catalog Index</title>
    </h:head>
    <h:body>
        You requested catalog item: <h:outputText value="#{catalog.item.name}"/>
    </h:body>
</html>

The above page requires additional functionality for the Expression Language (EL) references, such as viewParam value=”#{catalog.itemId}”, viewAction action=”#{catalog.loadItem}”, and outputText value=”#{catalog.item}”. Below is an example of a CDI managed bean (referred to as a backing bean) that provides the required functionality for the view:

@Named("catalog")
@RequestScoped
public class CatalogViewPage {
  private int id;
  private Item item;

  public String loadItem() {
    item = // load the item (which contains a "name" field).
    return null;
  }

  // Getters and setters...
}

JSF 2.2 introduces Faces Flows, which provide an encapsulation of related pages and corresponding backing beans as a module. This module has well-defined entry and exit points defined by the application developer. Each flow resides in its own folder within the web-root directory, and contains a *-flow.xml file. Flow XML files may be empty if no configuration is required.

Example flow layout:

src/main/webapp/
    catalog/
        item.xhtml
    purchase/
        purchase-flow.xml
        1-cart.xhtml
        2-checkout.xhtml
        3-confirm.xhtml

The newly introduced CDI @FlowScoped annotation defines the scope of a bean in the specified flow. This enables automatic activation/passivation of the bean when the scope is entered/exited:

@FlowScoped("flow1")
public class MyFlow1Bean {
    String address;
    String creditCard; 
    //. . .                   
} 

A new EL object for flow storage, #{flowScope}, is also introduced.

<h:inputText id=“input” value=“#{flowScope.value}” />

Flows may also be defined as CDI classes with producer methods annotated with @FlowDefinition:

class CheckoutFlow implements Serializable {
    @Produces
    @FlowDefinition
    public Flow defineFlow(@FlowBuilderParameter FlowBuilder flowBuilder) {
        ... 
    }
}

JSF 2.2 defines Resource Library Contracts, a library of templates and associated resources that can be applied to an entire application in a reusable and interchangeable manner. A configurable set of views in the application will be able to declare themselves as template-clients of any template in the resource library contract.

JSF 2.2 introduces passthrough attributes, which allow listing of arbitrary name/value pairs in a component that are passed straight through to the user agent without interpretation by the UIComponent or Renderer.

Example passthrough attribute:

<html ... xmlns:p="http://xmlns.jcp.org/jsf/passthrough"
   <h:form prependId="false">
   <h:inputText id="itemId" p:type="number" value="#{catalog.id}" 
             p:min="1" p:max="1000000" p:required="required" 
             p:title="Enter an Item ID">
        ...

This will cause the following output HTML to be generated:

<input id=“itemId” type=“number” value=“1” min=“1” max=“1000000”
    required=“required” title=“Enter an Item ID”>

Public API from javax.faces.*:

Flow Runtime representation of a Faces Flow.
@FlowScoped CDI scope that associates the bean to be in the scope of the specified Flow.
Section 15

Java Transaction API 1.2

JSR-344

The Java Transaction API enables distributed transactions across multiple X/Open XA resources such as databases and message queues in a Java application. The API defines a high-level interface, annotation, and scope to demarcate transaction boundaries in an application.

The UserTransaction interface enables the application to control transaction boundaries programmatically by explicitly starting and committing or rolling back a transaction.

@Inject UserTransaction ut;
ut.begin();
…
ut.commit();

ut.rollback() can be called to rollback the transaction.

JTA 1.2 introduces the @javax.transaction.Transactional annotation that enables one to declaratively control transaction boundaries on POJOs. This annotation can be specified at both the class and method level, where method-level annotations override those at the class level.

@Transactional
class MyBean {
    . . .
}

All methods of this bean are executed in a transaction managed by the container. This support is provided via an implementation of CDI interceptors that conduct the necessary suspending, resuming, etc.

JTA 1.2 also introduces a new CDI scope @TransactionScoped. This scope defines a bean instance whose lifecycle is scoped to the currently active JTA transaction.

Public API from javax.transaction.*:

UserTransaction Allows an application to explicitly manage application boundaries
@Transactional Annotation that provides the application the ability to declaratively control transaction boundaries on CDI-managed beans, as well as classes defined as managed beans.
@TransactionScoped Annotation that specifies a standard CDI scope to define bean instances whose lifecycle is scoped to the currently active JTA transaction.

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