Eric Bloch wrote:
Hey there,
I'm a developer on another Java open source project and I've noticed that cocoon shares some similar problems with our project.
In particular, delployments of our webapp see a variety of different and sometimes _very_ difficult to understand class-loading conflicts in different servlet containers.
And we'd like to come to some real solution to avoid these in the future. I'm wondering if cocoon developers have any good advice here.
FYI, we are actually considering re-building the java classes in *every* external jar we'd put in our web app's WEB-INF directory and name-spacing *every* external class with our namepsace, but this is costly in terms of maintenance and is non-trivial with code that does reflection, etc...
We've also considered writing our own class-loader but we think this won't solve the problem (and could make it worse, in fact).
Actually, it writing your own classloader *does* solve the problem. Cocoon provided a so-called "paranoid" block providing a "ParanoidCocoonServlet". This servlet loads the Cocoon servlet (or any other servlet through a config in web.xml) in a ParanoidClassLoader that shields the webapp's classes from the upper-level classloaders.
Shielding means that classes and resources are always looked up _first_ in the webapp before delegating to the parent classloader. Up to now, this has always saved my life in crazy classloading environments ;-)
More info at http://wiki.apache.org/cocoon/EndorsedLibsProblem
You can also browse the source at http://svn.apache.org/viewcvs.cgi/cocoon/trunk/src/blocks/paranoid/
ps... our project is described at http://openlaszlo.org
We know it, and are happy to see you here :-)
There was a discussion here when you went opensource and we'd love to have a "LaszloSerializer" in Cocoon. Actually, it's already partly done (see http://blog.reverycodes.com/archives/000032.html)
Sylvain
-- Sylvain Wallez Anyware Technologies http://www.apache.org/~sylvain http://www.anyware-tech.com { XML, Java, Cocoon, OpenSource }*{ Training, Consulting, Projects }
