Tom Rutchik created FELIX-5943:
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Summary: Felix Framework / Resolver Dependency
Key: FELIX-5943
URL: https://issues.apache.org/jira/browse/FELIX-5943
Project: Felix
Issue Type: Improvement
Components: Framework
Reporter: Tom Rutchik
The packaging of Felix framework and resolver seems not to be done in an OSGI
manner. "Org.apache.felix.framework" and "org.apache.felix.resolver" sources
are separate components, but are combined together in the resultant
"org.apache.felix.framework" jar file. It's not specified as a dependency but
seems to be assembled in a copy and paste manner.
The reason its done this way is probably due to the dependency of
"org.apache.felix.resolver" on an earlier version of the Felix framework.
"Org.apache.felix.framework" has as a dependency on "org.apache.felix.resolver"
and vice-a-versa. This cyclic specification is what makes it problematic and
why the assemble was done in this copy and paste manner. Obviously, the
packaging of the two sources as one jar makes for a simple and convienient one
jar dependence for embedding Felix into an application.
I discovered this issue, when I added the framework source to my application
and then discovered that the framework required the Resolver class which was
missing, so I added a dependency for the Resolver in my application. This
appeared to work, until some magic threshold was hit that cause the class
resolution order to change. What I discovered was that I had two different
copies of "org.osgi.framework.Version" in my application. For a while, I was
getting the newer version of "Version" that contained the "valueOf" method in
it. When that magical threshold was hit, it caused me to get the older version
of "Version" which didn't have the "valueOf" method in it, which cause the code
to crash. A tough problem to track down. The root cause, IMHO, however comes
back to an improper specification of the dependency. I think it fair to say
the Felix framework and resolver components aren't constructed in a manner
congruent with OSGI principals.
Embedding the source into a application rather then adding a jar dependency can
be useful to developers who kind-a wants to look-behind-the-curtain if they are
running into some non-obvious issues with their OSGI embedded environment.
It's often a lot little easier to debug in this configuration.
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