CODEWITHSUNDEEP
javamultithreadingjsfasynchronousejb-3.1
HaveANiceDay
HaveANiceDay

Reputation: 51

How to cancel a asynchronously fired thread with returning Future?

I spend hours of research my problem, but i find a solution.

I fire a thread with the @Asynchronous annotation and give a Future object back, so far so good. BUT, if I trie to cancel the future, it seems that the command doesn't cancel anything.

JSF file

    <?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://xmlns.jcp.org/jsf/html">
    <h:head>
        <title>Facelet Title</title>
    </h:head>
    <h:body>
        <h:form>
            <h:commandButton actionListener="#{threadHandler.start()}" value="start"/>
            <h:commandButton actionListener="#{threadHandler.stop()}" value="stop"/>
        </h:form>
    </h:body>
</html>

Java handler

    /*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package com.jsf.example;

import java.util.concurrent.Future;
import javax.ejb.Stateless;
import javax.inject.Inject;
import javax.inject.Named;

@Named("threadHandler")
@Stateless
public class Handler {

    Future future;
    @Inject
    MethodPool pool;

    public void start(){
        System.out.println("start thread");
        future = pool.run();
        System.out.println("finish thread start");
    }

    public void stop(){
        System.out.println("future.cancel " + future.cancel(true));
    }
}

Java thread

 /*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package com.jsf.example;

import java.util.concurrent.Future;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.ejb.AsyncResult;
import javax.ejb.Asynchronous;
import javax.ejb.Stateless;


@Stateless
public class MethodPool {

    @Asynchronous
    public Future run(){
        System.out.println("start run");
        Integer runCondition = 1;
        while(runCondition > 0){
            try {
                // simulate heavy stuff
                Thread.sleep(1000);
                System.out.println(". ");
            } catch (InterruptedException ex) {
                Logger.getLogger(MethodPool.class.getName()).log(Level.SEVERE, null, ex);
            }

        }
        return new AsyncResult("finish run");
    }

}

*EDIT: THX @bkail *

I will post the working code example for the next one who is desperate;) 

@Resource
    private SessionContext sessionContext;

@Asynchronous
    public Future run(){
        System.out.println("start run");
        while(sessionContext.wasCancelCalled() == false){
            try {
                // simulate heavy stuff
                Thread.sleep(1000);
                System.out.println(". ");
            } catch (InterruptedException ex) {
                Logger.getLogger(MethodPool.class.getName()).log(Level.SEVERE, null, ex);
            }

        }
        return new AsyncResult("finish run");
    }

Upvotes: 2

Views: 1491

Answers (1)

Brett Kail
Brett Kail

Reputation: 33936

EJB uses cooperative cancelling, so passing cancel(interrupt=true) does not actually interrupt. Instead, it sets a flag on the method invocation. In your EJB, use @Resource SessionContext context;, and then check context.wasCancelCalled() to check if cancel(interrupt=true) was called.

Upvotes: 4

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