Problem loading classes with OSGi classloaders
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Key: OPENJPA-311
URL: https://issues.apache.org/jira/browse/OPENJPA-311
Project: OpenJPA
Issue Type: Bug
Affects Versions: 0.9.7, 0.9.6, 0.9.0, 1.0.0
Reporter: Michael Dick
Assignee: Michael Dick
Fix For: 1.0.0
The root of the problem appears to be in the
GeneratedClasses.getMostDerivedLoader method.
GetMostDerivedLoader takes two classes (class1 & class2) gets their respective
classloaders (classloader1, & classloader2 respectively) and looks for a match.
If the classloaders are not the same, and neither is null it calls getParent on
classloader1 until classloader2 is found, or until there are no more parent
loaders. If a match is found the mostDerivedLoader is considered to be
classloader1, if no match is found we use classloader2.
The problem comes in when you have an OSGI classloader involved. The specific
scenario I ran into has classloader1 calling getParent and encountering an OSGI
gateway classloader, but not classloader2 (which is behind the OSGI gateway).
Conceptually classloader2 is a parent of classloader1, but the OSGI gateway
classloader hides it and we aren't able to find it.
I'm probably mangling the OSGI terminology a bit but I think this captures the
essence of the problem.
It seems to me that the intent of the getMostDerivedLoader is to ensure that we
use a classloader that has the "right" version of class2, preferring
classloader1. If that's the case then would it be possible to just try to load
class2 from classloader1 and compare the result to the original class? I
believe this approach would work for OSGI classloaders, but I have a nagging
feeling that I'm missing something.
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