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Join For FreeOriginally authored by Josh Long on the Spring blog
Spring Integration 4.1 was just released and it includes a lot of great new features! One of my favorites? Smart integration with the Spring 4 WebSocket support. Now you can compose a integration flow whose final destination is a WebSocket client. There is also support for acting as the client to a WebSocket service.
In order to compile it, you will need Java 8 (we make heavy use of lambas here) and the following Maven dependencies:
- groupId:
org.springframework.integration, artifactId:spring-integration-java-dsl, version:1.0.0.RC1. - groupId:
org.springframework.integration, artifactId:spring-integration-websocket, version:4.1.0.RELEASE. - groupId:
org.springframework.boot, artifactId:spring-boot-starter-websocket,version:1.2.0.RC1.
In order to resolve those dependencies you will need the snapshot and milestone Maven repositories.
All clients listening on /names will receive whatever message is sent into therequestChannel channel. A Spring 4 MessageChannel is a named conduit - more or less analogous to a java.util.Queue<T>. This example uses the Spring Integration Java configuration DSL on top of the new Spring Integration 4.1 web socket support. Here’s the example:
package demo ;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.*;
import org.springframework.integration.channel.DirectChannel;
import org.springframework.integration.dsl.IntegrationFlow;
import org.springframework.integration.dsl.support.Function;
import org.springframework.integration.websocket.ServerWebSocketContainer;
import org.springframework.integration.websocket.outbound.WebSocketOutboundMessageHandler;
import org.springframework.messaging.*;
import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
import org.springframework.messaging.support.MessageBuilder;
import org.springframework.web.bind.annotation.*;
import java.util.concurrent.Executors;
import java.util.stream.Collectors;
/**
* @author Artem Bilan
* @author Josh Long
*/
@Configuration
@ComponentScan
@EnableAutoConfiguration
@RestController
public class Application {
public static void main(String args[]) throws Throwable {
SpringApplication.run(Application.class, args);
}
@Bean
ServerWebSocketContainer serverWebSocketContainer() {
return new ServerWebSocketContainer("/names").withSockJs();
}
@Bean
MessageHandler webSocketOutboundAdapter() {
return new WebSocketOutboundMessageHandler(serverWebSocketContainer());
}
@Bean(name = "webSocketFlow.input")
MessageChannel requestChannel() {
return new DirectChannel();
}
@Bean
IntegrationFlow webSocketFlow() {
return f -> {
Function<Message , Object> splitter = m -> serverWebSocketContainer()
.getSessions()
.keySet()
.stream()
.map(s -> MessageBuilder.fromMessage(m)
.setHeader(SimpMessageHeaderAccessor.SESSION_ID_HEADER, s)
.build())
.collect(Collectors.toList());
f.split( Message.class, splitter)
.channel(c -> c.executor(Executors.newCachedThreadPool()))
.handle(webSocketOutboundAdapter());
};
}
@RequestMapping("/hi/{name}")
public void send(@PathVariable String name) {
requestChannel().send(MessageBuilder.withPayload(name).build());
}
}
The IntegrationFlow is simple. For each message that comes in, copy it and address it to each listening WebSocket session by adding a header having theSimpMessageHeaderAccessor.SESSION_ID_HEADER, then send it the outboundwebSocketOutboundAdapter which will deliver it to each listening client. To see it work, openhttp://localhost:8080/ in one browser window, and thenhttp://localhost:8080/hi/Spring in another. There is a simple client demonstrated in this techtip's code repository.
There is great documentation on how to use the web socket components in Spring Integration 4.1 documentation. There's a more inspiring example in the Spring Integration samples directory, too.
Published at DZone with permission of Pieter Humphrey, DZone MVB. See the original article here.
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