Issue with Asynchronous Servlet: onStartAsync(AsyncEvent event) never called

[Namitha karupaiya]

Consider the following code fragment which may appear in an Asynchronous Servlet:

final AsyncContext ac = request.startAsync(); //AsyncContext is created
  
   ac.addListener(new AsyncListener() { //AsyncListener is added to AsyncContext 
   
 public void onComplete(AsyncEvent event) throws IOException {
         }
   
public void onTimeout(AsyncEvent event) throws IOException {
        }

    public void onError(AsyncEvent event) throws IOException {
          }
   
 public void onStartAsync(AsyncEvent event) throws IOException { //This method will never be called because this event has already occurred before adding this listener
       }

});

According to the specification onStartAsync(AsyncEvent event) method should be called when startAsync() is called on the request object.
According to my understanding onStartAsync(AsyncEvent event) will never be called because the AsyncListener() is added to the AsyncContext AFTER calling startAsync(). (& there is no way to add the the AsyncListener() before calling startAsync())

Am I missing anything?

[Namitha karupaiya]

Any small help from anyone will be greatly appreciated.

Thanks.

[Bear Bibeault]

I think you may be a bit ahead of the curve. Not many people are using a Servlet 3.0 container yet...

[Ryan Slack]

startAsync() can be called multiple times, and always returns the same instance of AsyncContext.

startAsync():

...
This method clears the list of AsyncListener instances (if any) that were registered with the AsyncContext returned by the previous call to one of the startAsync methods, after calling each AsyncListener at its onStartAsync method.

Subsequent invocations of this method, or its overloaded variant, will return the same AsyncContext instance, reinitialized as appropriate.

Returns:
the (re)initialized AsyncContext

If you want your listener to stay registered, even if some other code calls startAsync(), it needs to be re-registered in it's onStartAsync(AsyncEvent) method.

[Namitha karupaiya]

Great explanation! Thank you!