OSGi service injection and service publishing by means of CDI
annotations is now possible with Pax CDI 0.2.0-SNAPSHOT for non-web
applications.
The next major step I'd like to take is to make this work for WABs, in
combination with Pax Web.
I'm not sure if this can be achieved without creating some new extension
points in Pax Web, so in short, my questions are:
1) Does Pax Web offer hooks for other extenders to customize the web app
being published?
2) If not, would this be a feasible extension?
Some background and ideas:
Both Pax Web and Pax CDI use the extender pattern, listening to bundle
start events and checking if the bundle contains a web.xml or a
beans.xml, respectively.
Pax CDI extends a bundle with a CDI container, Pax Web extends a bundle
with a servlet context and publishes it as a web application.
For a CDI-enabled WAB, the two extenders have to be coordinated - it is
not enough to let them process the same bundle in arbitrary order, or
else the web context might be running and servicing requests before the
CDI container has been initialized, or the CDI container might not be
aware of web object injection targets like servlets and filters.
To make this work, it might be sufficient for Pax Web to allow a
customizer to
- add a ServletContextListener (or a ServletContextInitializer)
- replace the classloader to be used as web app classloader
Motivation for the context listener:
Both OpenWebBeans and Weld require a context listener in web-only
environments (Tomcat, Jetty), whereas full Java EE 6 containers add them
automatically behind the scenes to bootstrap the CDI container.
Motivation for the classloader:
The classloader for the CDI container must be able to see the extended
bundle, the CDI provider bundle and any bundles with CDI portable
extensions (including Pax CDI). Pax CDI builds a multi-bundle delegating
classloader and sets this as TCCL to make Weld and OpenWebBeans happy -
not very nice, but Weld and OpenWebBeans do not provide any more
OSGi-friendly SPIs at the moment.
Achim and other Pax Web champions, I'd love to hear your opinions on
this, as I'm not too intimate with Pax Web internals...
Best regards,
Harald
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