EJB 3.1 introduced a simple mechanism for asynchronous invocation. This post presents such an example with a Singleton session bean and its JUnit test case. 2 styles of asynchronous EJB invocations are used:

(1) fire-and-forget asynchronous methods having void return type.

(2) retrieve-result-later asynchronous methods having Future<?> return type.

package test;

import java.util.concurrent.Future;
import javax.ejb.Asynchronous;
import javax.ejb.AsyncResult;
import javax.ejb.Singleton;

@Singleton
@Asynchronous
public class AsyncBean {
    @Asynchronous  //this line can be omitted
    public void ignoreResult(int a, int b) {
        // the client doesn't care what happens here
    }

    @Asynchronous  //this line can be omitted
    public Future<Integer> longProcessing(int a, int b) {
        return new AsyncResult<Integer>(a * b);
    }
}

Since the class is annotated with @Asynchronous, all business methods are asynchronous. The method-level @Asynchronous is therefore redundant, and kept there for illustration purpose.

package test;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import javax.ejb.embeddable.EJBContainer;
import javax.naming.Context;
import junit.framework.TestCase;

public class AsyncBeanTest extends TestCase {
    private EJBContainer container;
    private Context namingContext;
    private AsyncBean asyncBean;

    @Override
    protected void setUp() throws Exception {
        super.setUp();
        container = EJBContainer.createEJBContainer();
        namingContext = container.getContext();
        asyncBean = (AsyncBean) namingContext.lookup("java:global/testApp/AsyncBean");
    }

    @Override
    protected void tearDown() throws Exception {
        super.tearDown();
        container.close();
    }

    public final void testIgnoreResult() {
        asyncBean.ignoreResult(0, 0); // fire and forget
        System.out.println("Proceed without waiting for the async method result.");
    }

    public final void testLongProcessing() throws InterruptedException, ExecutionException {
        Future<Integer> futureResult = asyncBean.longProcessing(8, 9);
        System.out.println("Proceed to other tasks and check async method result later.");
        Integer intResult = futureResult.get();
        System.out.println("The prior async method returned " + intResult);
    }
}

I've tested this example with GlassFish V3 in its embedded mode. It should work with any Java EE 6 application servers as well. The configureation (classpath, outputDir, etc) and how to run it are the same as EJB Lite testing with JUnit and embeddable container.