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Cancelling an @Asynchronous method with Future.cancel
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created by <a href="http://community.jboss.org/people/david_b">david_b</a> in <i>EJB3</i> - <a href="http://community.jboss.org/message/583431#583431">View the full discussion</a>
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<div class="jive-rendered-content"><p>I am writing an enterprise Java application that uses aynchronous EJB 3.1 methods to execute a number of tasks in parallel. The app is currently running on JBoss AS 6.0.0 Final.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>To support cancelling a long running task I have been attempting to use the Future interface. Unfortunately calling <code>future.cancel(true)</code>appears to have no effect on the session context of the bean executing the task, despite the fact that cancel is returning <code>true</code>.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I have a simple interface:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>public interface AsyncInterface</p><p>{</p><p>    Future run() throws Exception;</p><p>} </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>With a bean implementation as follows:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>@Stateless@Remote(AsyncInterface.class)public class AsyncBean{    @Resource SessionContext myContext;    @Asynchronous    public Future(result);     }} </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The asynchronous method is called from another Stateless EJB like so:</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>InitialContext ctx = new InitialContext();AsyncInterface async = (AsyncInterface)ctx.lookup("AsyncBean/remote");Future future = async.run();if( future.cancel(true) ){     System.out.println("future.cancel() returned true");}else{     System.out.println("future.cancel() returned false");} </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>The output from the AsyncBean is an endless stream of "Working"; it never detects the cancellation.</p><p style="min-height: 8pt; height: 8pt; padding: 0px;"> </p><p>I haven't found much sample code using Futures to cancel an @Asynchronous EJB call. Is using the session context the correct way of checking for cancellation? Is there a better method for cancelling the asynchronous call?</p></div>
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