On Sep 15, 2010, at 10:51 PM, David Jencks wrote:
>
> On Sep 15, 2010, at 9:58 PM, David Jencks wrote:
>
>> I think this is how AsyncContextImpl creates async listeners (lines 228ff)
>>
>> @Override
>> public <T extends AsyncListener> T createListener(Class<T> clazz)
>> throws ServletException {
>> T listener = null;
>> try {
>> listener = clazz.newInstance();
>> } catch (InstantiationException e) {
>> ServletException se = new ServletException(e);
>> throw se;
>> } catch (IllegalAccessException e) {
>> ServletException se = new ServletException(e);
>> throw se;
>> }
>> return listener;
>> }
>>
>>
>>
>> but the 3.0 spec section 15.5 page 179 says
>>
>> Annotations must be supported on the following container managed classes
>> that implement the following interfaces and are declared in the web
>> application deployment descriptor or using the annotations defined in
>> Section 8.1, “Annotations and pluggability” on page 8-61 or added
>> programmatically.
>>
>> and includes AsyncListener in the table following.
>>
>> So shouldn't this be using the instance manager to create the instance so
>> the resource injection machinery can do its stuff?
>>
>>
>> Secondly, if you do try to register an AsyncListener with the
>> ServletContext so it can be scanned for annotations, aside from not actually
>> scanning it, it quickly gets to this code (ApplicationContext lines 1262 ff)
>>
>> @Override
>> public <T extends EventListener> void addListener(T t) {
>> if (!context.getState().equals(LifecycleState.STARTING_PREP)) {
>> throw new IllegalStateException(
>> sm.getString("applicationContext.addListener.ise",
>> getContextPath()));
>> }
>>
>> // TODO SERVLET3
>> // throw UnsupportedOperationException - if this context was passed to
>> the
>> // {...@link
>> ServletContextListener#contextInitialized(javax.servlet.ServletContextEvent)}
>> // method of a {...@link ServletContextListener} that was not declared
>> // in web.xml, a web-fragment or annotated with {...@link WebListener}.
>>
>> boolean match = false;
>> if (t instanceof ServletContextAttributeListener ||
>> t instanceof ServletRequestListener ||
>> t instanceof ServletRequestAttributeListener ||
>> t instanceof HttpSessionAttributeListener) {
>> context.addApplicationEventListener(t);
>> match = true;
>> }
>>
>> if (t instanceof HttpSessionListener
>> || (t instanceof ServletContextListener &&
>> newServletContextListenerAllowed)) {
>> context.addApplicationLifecycleListener(t);
>> match = true;
>> }
>>
>> if (match) return;
>>
>> throw new IllegalArgumentException(sm.getString(
>> "applicationContext.addListener.iae.wrongType",
>> t.getClass().getName()));
>>
>> }
>>
>>
>> which doesn't accept AsyncListeners. (of course it shouldn't do anything
>> with then).
>>
>> Thoughts?
>>
>> thanks
>> david jencks
>>
>
> BTW I opened bug 49937 with fixes that work for me for these problems.
>
> david jencks
>
The situation seems to be more complicated than I thought at first.
As noted above, section 15.5 clearly indicates annotation based resource
injection is supported for all servlet related listeners including
AsyncListener, and that these can be specified in the xml deployment
descriptor, via annotation, or by adding programatically.
However....
4.4.3 indicates that an AsyncListener cannot be added programatically
4.4.3.5 indicates that resource injection is not supported for listeners added
programatically unless the listener is a managed bean. I think this directly
contradicts 15.5.
8.1.4 indicates that an AsyncListener cannot be annotated with @WebListener
11.3.2 says
Listener classes are declared in the Web application deployment descriptor
using the listener element. They are listed by class name in the order in which
they are to be invoked. Unlike other listeners, listeners of type AsyncListener
may only be registered (with a ServletRequest) programmatically.
I can't figure out what this is supposed to mean. It might mean that you
aren't allowed to list an AsyncListener in your web.xml, or it might mean that
you can, but to use it you have to explicitly add it to an AsyncContext.
Despite the contradictions in the spec, it seems pretty clear that an
asyncListener can be a managed bean and thus be subject to resource injection.
It might also be possible for it to be listed in web.xml, have a @WebListener
annotation, and be "added" programatically so it can be scanned for normal ee
resource injection annotations (depending on how much weight you put on 15.5
compared with the other sections). So, I think that the
AsyncContext.createListener method should use the instance manager in any case.
I think it makes sense to relax the restrictions on @WebListener and
programatically adding AsyncListeners as well (i.e. giving priority to 15.5
rather than all the other sections) since it doesn't break anything and is more
powerful.
thanks
david jencks
>
>>
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