Chapter 69. ListenerService

69.1. Asynchronous Event Broadcast

69.1. Asynchronous Event Broadcast

Basicaly, ListenerService used to store Listeners and broadcast events to them.

ListenerService event broadcasting works in next way - it takes a destination listeners and executes event on those listeners.

But, some events may take a lot of time, so idea to make event processing asynchronous is usefull.

What do I need to make my listener asynchronous?

- It's very simple, just mark your Listener implementation as @Asynchronous.

@Asynchronous
class AsynchListenerWithException<S,D> extends Listener<S,D>
{
   @Override
   public void onEvent(Event<S,D> event) throws Exception
   {
      // some expensive operation
   }
}

Now, our AsynchListener will be executed in separate thread by ExecutorService.

By default, ExecutoreService configured with thread pool size 1, you can change it in configuration:

   <component>
      <key>org.exoplatform.services.listener.ListenerService</key>
      <type>org.exoplatform.services.listener.ListenerService</type>
      
      <init-params>
         <value-param>
            <name>asynchPoolSize</name>
            <value>5</value>
         </value-param>
      </init-params>

   </component>