Building a Spring Integration 4.1 WebSocket Endpoint
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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.
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