Here is the syntax of java.util.concurrent.ThreadPoolExecutor. Please see the <a href="http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ThreadPoolExecutor.html#ThreadPoolExecutor(int, int, long, java.util.concurrent.TimeUnit, java.util.concurrent.BlockingQueue)" target="_blank" class="news_link" title="ThreadPoolExecutor JavaDoc">Javadoc for more</a>.



<pre class="brush: bash">
public ThreadPoolExecutor(int corePoolSize,
 int maximumPoolSize,
 long keepAliveTime,
 TimeUnit unit,
 BlockingQueue&lt;Runnable> workQueue)
</pre>



<h3>
Our example
</h3>


<pre class="brush: java; highlight: [15,21]">
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Future;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;

public class UpdateListener implements ServletContextListener {

 private static ExecutorService executor;

 @Override
 public void contextInitialized(ServletContextEvent cs) {
 createExecutor();
 cs.getServletContext().log("Executor service started !");
 }

 @Override
 public void contextDestroyed(ServletContextEvent cs) {

 executor.shutdown();

 cs.getServletContext().log("Executor service shutdown !");
 }

 public static synchronized void submitTask(Runnable runnable) {
 if (executor == null) {
 createExecutor();
 }
 executor.submit(runnable);
 }

 public static synchronized Future&lt;String> submitTask(Callable callable) {
 if (executor == null) {
 createExecutor();
 }
 return executor.submit(callable);
 }

 static void createExecutor() {
 executor = new ThreadPoolExecutor(
 1,
 3,
 100L,
 TimeUnit.MILLISECONDS,
 new LinkedBlockingQueue&lt;Runnable>());

 }
}
</pre>


 
For our ServletContextListener to listen to init and destroy (line 15 and line 21), our class must be registered in the deployment descriptor 

(web.xml) of the application. 



<pre class="brush: xml">
&lt;listener>
 &lt;listener-class>info.kahimyang.TaskExecutorListener&lt;/listener-class>
&lt;/listener>
</pre> 



If you are using EE6, it can also be annotated with WebListener instead of updating your web.xml. 



<pre class="brush: java">
@WebListener
public class TaskExecutorListener implements ServletContextListener {
	// our ServletListener class above
}
</pre>


<h3>
Client code
</h3>


Using our class takes implementing Runnable or Callable interface. The inlined code fragment that follows should accomplish 

submiting a task for execution by our Executor from any of your class or beans. Note that our thread pool is independent of any JSF session.



<pre class="brush: java">
TaskExecutorListener.submitTask (new Runnable () {
 @Override
 public void run() {
	// the actual job
 }

});
</pre>



The example above, does not return any value or status of the task. Using Callable enables client code to return a 

value from the task. See below.



<pre class="brush: java">
Future future = TaskExecutorListener.submitTask (new Callable() {
 @Override
 public String call () {
 String result;
	// the actual task
	return result;
 }

});

try {
	String status = future.get (); // blocks
}
catch (Exception e) {}
</pre>



For more other options about using the Java Executor framework please see <a 

href="http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/package-summary.html" target="_blank" class="news_link" 

title="java.util.Concurrent package">java.util.Concurrent</a> package. 




That's it. Good luck.

Asynchronous tasks in JSF applications