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From Jarek Gawor <jga...@gmail.com>
Subject rfc66 fun
Date Wed, 20 Jan 2010 19:38:14 GMT
Hey,

For last few days I've been looking into getting the rfc66 extender
going in Geronimo but I ran into a problem. As previously mentioned on
this list, the idea for the extender was to call the Tomcat/Jetty
ModuleBuilders with a bundle as an input and once the deployment
process was done start the generated configuration. All without
creating any additional temporary or permanent bundles.

Because we don't have a single classloader that can load all the
gbeans within the configuration, David Jencks added a special
"classSource" attribute to GBeanData which can be used to figure out
the right Bundle to load the gbean class. Now, since we use Java
serialization to save and load gbeans, we actually need to set the
right classloader when we deserialize the gbean. That is, during
deserialization as soon as we read the "classSource" we need to lookup
and set the right classloader and then read the rest of the gbean
data. This should (and seems to) work when all the attributes of the
gbean are accessible from the same classloader. But what about if the
gbean has some attribute with some values from different classloaders?
For example, the Map object we build for jndi context can contain
objects from different classloaders. I'm not exactly sure what to do
about it. Although maybe having a custom ObjectOutputStream with
annotateClass() method that saves "classSource" type of info for each
unique class might work. Ideas?

Also, I'm dealing with lots of classloader issues since there is no
single classloader that load all the gbean classes and module classes.
A lot of Geronimo and other code assumes a single classloader and
resolving these problems is time consuming and not very fun (although
probably good in long term). So I'm wondering if we can still somehow
assemble a single classloader in the extender. For example, the
http://www.osgi.org/blog/2008/08/classy-solutions-to-tricky-proxies.html
post shows a classloader that delegates a number of different bundles.
Maybe we could use that in Geronimo especially since we can figure out
the bundles needed from the configuration environment information.

Thoughts?

Jarek

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