[weld-dev] Ordering of servlet listeners

[Dan Allen]

I've quoted some passages from the Servlet 3.0 spec to clarify.

As you know:

>
>       Prior to this release of the specification, listeners were invoked in
> a random order.

      As of servlet 3.0, the order in which listeners are invoked is defined
> in “Assembling

      the descriptor from web.xml, web-fragment.xml and annotations”


The spec acknowledges that:

                 Since the specification allows the application
> configuration resources to be

                 composed of multiple configuration files (web.xml and
> web-fragment.xml),

                 discovered and loaded from several different places in the
> application, the question

                 of ordering must be addressed.


The web.xml (or web-fragment.xml) must have a <name> element to participate
in ordering.

Since you are dealing with web.xml, you will need to use the absolute
ordering:

1. Absolute ordering: an <absolute-ordering> element in the web.xml.
   a. In this case, ordering preferences that would have been handled by
case 2
      below must be ignored.
   b. The web.xml MUST be processed before any of the web-fragments listed
in the
      absolute-ordering element.
   c. Any <name> element direct children of the <absolute-ordering> MUST be
      interpreted as indicating the absolute ordering in which those named
web-
      fragments, which may or may not be present, must be processed.
   d. The <absolute-ordering> element may contain zero or one <others />
      element. The required action for this element is described below. If
the
      <absolute-ordering> element does not contain an <others/> element,
      any web-fragment not specifically mentioned within <name /> elements
      MUST be ignored. Excluded jars are not scanned for annotated servlets,
filters
      or listeners. However, if a servlet, filter or listener from an
excluded jar is listed
      in web.xml or a non-excluded web-fragment.xml, then it's annotations
will
      apply unless otherwise excluded by metadata-complete.
      ServletContextListeners discovered in TLD files of excluded jars are
not
      able to configure filters and servlets using the programmatic APIs.
Any
      attempt to do so will result in an IllegalStateException. If a
discovered
      ServletContainerInitializer is loaded from an excluded jar, it will be
      ignored. Excluded jars are not scanned for classes to be handled by
any
      ServletContainerInitializer.
   e. Duplicate name exception: if, when traversing the children of
<absolute-
      ordering>, multiple children with the same <name> element are
encountered,
      only the first such occurrence must be considered.

Hopefully you can parse all that and get further along. I recommend you
checkout the spec for more details, and let us know your results!

-Dan

On Wed, Mar 24, 2010 at 3:20 AM, Nicklas Karlsson <nickarls at gmail.com>wrote:

> Hi,
>
>   I'm tinkering with the servlet listener -> CDI event bridge in the
> seam-servlet module and noticed that currently the WeldListener is placed
> last in the PostWebMetadataDeployer in weld-int.
> I changed this (and verified it with the debugger) but still my own servlet
> listener fires first (expecting the contexts to be up), causing problems.
> Any theories as to why this is? How could we guarantee that
> the WeldListener is the first one to fire?
>
> ---
> Nik
>
> _______________________________________________
> weld-dev mailing list
> weld-dev at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/weld-dev
>



-- 
Dan Allen
Senior Software Engineer, Red Hat | Author of Seam in Action
Registered Linux User #231597

http://mojavelinux.com
http://mojavelinux.com/seaminaction
http://www.google.com/profiles/dan.j.allen
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