JAX-RS 2.1 SSE Client API example using Glassfish 5 on Docker

Along with the Server API for SSE, JAX-RS 2.1 (part of Java EE 8) also has an equivalent client side API

Here is a quick peek – you can grab the project from Github

	@Singleton
	@Startup
	public class ProgrammaticSSEClient {

	Client sseClient;
	WebTarget target;

	@Resource
	TimerService tsvc;

	@PostConstruct
	public void init() {
	this.sseClient = ClientBuilder.newClient();
	this.target = this.sseClient.target("https://sse.now.sh");

	tsvc.createSingleActionTimer(15000, null);
	System.out.println("SSE client timer created");

	eventSource = SseEventSource.target(target).build();
	System.out.println("SSE Event source created……..");
	}

	SseEventSource eventSource;

	@Timeout
	public void client() {
	System.out.println("SSE Client triggered in thread "+ Thread.currentThread().getName());

	try {
	eventSource.register((sseEvent)
	-> {
	System.out.println("Events received in thread " + Thread.currentThread().getName());
	System.out.println("SSE event recieved —– " + sseEvent.readData());
	},
	(e) -> e.printStackTrace());

	eventSource.open();
	System.out.println("Source open ????? " + eventSource.isOpen());
	} catch (Exception e) {
	e.printStackTrace();
	}

	}

	@PreDestroy
	public void close() {
	eventSource.close();
	System.out.println("Closed SSE Event source..");
	sseClient.close();
	System.out.println("Closed JAX-RS client..");
	}
	}

we use a @Singleton EJB with @Startup
during initialization
- create a single action (one time) Timer i.e. @PostConstruct
- and instantiate the SSEEventSource – its a public SSE source
when the timer expires, the @Timeout annotated method gets triggered
- opens the SSE connection
- prints them out – this action is registered as a callback (written as a Java 8 lamda in this case)
Execution thread pool(s) – notice this in the logs
- the timer itself is triggered in the EJB thread pool
- SSE event callbacks are executed in the ManagedExecutorService thread pool (thanks to Java EE Concurrency Utilities)

To run using Docker

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