Asynchronous Actions

This feature is work-in-progress, and available in 1.7.0-SNAPSHOT. Requires a Servlet3+ container.

Description

Async Actions allows handler methods to behave in an asynchronous (Servlet3) fashion. This is mostly used for performance reasons, when a Stripes Action has to can connect to external services (e.g. a web service) in a non-blocking fashion.

Usage

Async event handlers must return void, and accept a single argument of type AsyncResponse :

signature

public void doSomething(AsyncResponse asyncResponse);

When handling such events, Stripes will start the asynchronous cycle, and let you complete by invoking one of the asyncResponse.complete() variants.

Examples

SimpleAsync

public class SimpleAsync implements ActionBean {
  
  public void simpleEvent(AsyncResponse asyncResponse) {
    // simple without really anything async...
    asyncResponse.complete(new ForwardResolution("/WEB-INF/stuff.jsp"));
  }
  
}

ReallyAsync

public class ReallyAsync implements ActionBean {
  
  public void asyncEvent(final AsyncResponse asyncResponse) {
	// submit to executor service
	ExecutorService executor = ... ; 
	executorService.submit(new Runnable() {
	   @Override
	   public void run() {
			// do anything in a separate thread and complete with a forward
			asyncResponse.complete(new ForwardResolution("/WEB-INF/stuff.jsp"));    
	   }
	});
  }
  
}

ReallyAsyncWithLambdas

public class ReallyAsyncWithLambdas implements ActionBean {
  
  public void asyncEventWithLambda(final AsyncResponse asyncResponse) {
	// submit to executor service
	ExecutorService executor = ... ; 
	executorService.submit(() -> {
		// do anything in a separate thread and complete with a forward
		asyncResponse.complete(new ForwardResolution("/WEB-INF/stuff.jsp"));    
	});
  }
  
}

NonBlockingClient

public class WithNonBlockingClient implements ActionBean {
  
  public void nonBlocking(final AsyncResponse asyncResponse) {
	// call non blocking http client
	httpClient.get('/foo/bar', httpResponse -> {
		// client completed : use http response
		httpResponse.xyz();
		// and complete...
		asyncResponse.complete(new ForwardResolution("/WEB-INF/stuff.jsp"));
	});
  }
  
}