# Async improvements

In JAXRS 2.0, you can build an asynchronous RESTful APIs as the following.

```java
@GET
public void getAsync(final @Suspended AsyncResponse res) {
    res.setTimeoutHandler(
            (ar) -> {
                ar.resume(Response.status(Response.Status.SERVICE_UNAVAILABLE)
                        .entity("Operation timed out --- please try again.").build());
            }
    );
    res.setTimeout(1000, TimeUnit.MILLISECONDS);
    executor.submit(() -> {
        //do long run operations.
        try {
            LOG.log(Level.INFO, " execute long run task in AsyncResource");
            //Thread.sleep(new Random().nextInt(1005));
            Thread.sleep(500);
        } catch (InterruptedException ex) {
            LOG.log(Level.SEVERE, "error :" + ex.getMessage());
        }
        res.resume(Response.ok("asynchronous resource").build());
    });
}
```

Inject `@Suspended AsyncResponse res` as the method parameter, call `res.resume()` to return response result asynchronously.

Or combined with EJB `@Asynchronous`.

```java
@GET
@Asynchronous
public void getAsync(final @Suspended AsyncResponse res) {

    //perform long run operations.
    try {
        LOG.log(Level.INFO, " execute long run task in EjbAsyncResource");
        Thread.sleep(500);
    } catch (InterruptedException ex) {
        LOG.log(Level.SEVERE, "error :" +ex.getMessage());
    }

    res.resume(Response.ok("Asynchronus EJB resource").build());
}
```

JAXRS 2.1 allow you return a `CompletionStage` directly.

```java
@GET
public CompletionStage<String> getAsync() {
    CompletionStage<String> cs = CompletableFuture
            .<String>supplyAsync(
                    () -> {
                        try {
                            LOG.log(Level.INFO, " execute long run task in CompletionStageResource");
                            Thread.sleep(500);
                        } catch (InterruptedException ex) {
                            LOG.log(Level.SEVERE, "error :" +ex.getMessage());
                        }
                        return "return CompletableFuture instead of @Suspended";
                    }
                   // , executor
            );

    return cs;
}
```

Grab the [source codes](https://github.com/hantsy/ee8-sandbox) from my GitHub account, and have a try.


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