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https://issues.apache.org/jira/browse/OPENJPA-1410?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12846563#action_12846563
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Jeremy Bauer commented on OPENJPA-1410:
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I committed a change under rev 924395 that disables the dynamic enhancer if the
OpenJPA instrumentation factory is not loaded by the system classloader. In a
multi-tier classloader environment (Tomcat, JEE app server, etc.) the OpenJPA
jar was being loaded by the container classloader and then loaded a second time
into the system classloader (as an agent). This lead to linkage issues since
OpenJPA classes were loaded from multiple loaders and there ended up being a
mix of classes in the execution path.
After correcting this issue, the subclassing enhancer is working again (but
that has its own set of deficiencies and is not recommended) - but agent-based
enhancement (-javaagent:...) is not. This is not a result of my change, there
is some other issue. I plan on looking into that next.
As of rev 924395 the openjpa.DynamicEnhancementAgent=false property should no
longer be required, but build time enhancement of entities may still be
necessary.
> Class linkage exception when creating an EMF with OpenJPA M3
> ------------------------------------------------------------
>
> Key: OPENJPA-1410
> URL: https://issues.apache.org/jira/browse/OPENJPA-1410
> Project: OpenJPA
> Issue Type: Bug
> Components: validation
> Affects Versions: 2.0.0-M3, 2.0.0-beta, 2.0.0-beta2
> Environment: Tomcat and Glassfish, OpenJPA M3
> Reporter: Jeremy Bauer
> Assignee: Jeremy Bauer
> Priority: Critical
> Fix For: 2.0.0
>
>
> Posted by Seth Jackson on the user forum[1].
> It appears something was modified in OpenJPA 2.0 M3 from M2 that causes a
> LinkageError.
> In my current environment, I've tested both Glassfish and Tomcat using M2
> and M3. M2 runs without problems, but M3 throws a linkage error as follows:
> Caused by: java.lang.LinkageError: loader constraint violation: loader
> (instance of sun/misc/Launcher$AppClassLoader) previously initiated loading
> for a different type with name
> "org/apache/openjpa/conf/OpenJPAConfiguration"
> at java.lang.ClassLoader.defineClass1(Native Method)
> at java.lang.ClassLoader.defineClass(ClassLoader.java:621)
> at
> java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
> at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
> at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
> at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
> at java.security.AccessController.doPrivileged(Native Method)
> at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
> at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
> at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
> at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
> at
> org.apache.openjpa.persistence.validation.ValidationUtils.setupValidation(ValidationUtils.java:53)
> at
> org.apache.openjpa.persistence.PersistenceProviderImpl.loadValidator(PersistenceProviderImpl.java:290)
> at
> org.apache.openjpa.persistence.PersistenceProviderImpl.createEntityManagerFactory(PersistenceProviderImpl.java:97)
> at
> org.apache.openjpa.persistence.OpenJPAPersistence.createEntityManagerFactory(OpenJPAPersistence.java:128)
> at
> org.apache.openjpa.persistence.OpenJPAPersistence.createEntityManagerFactory(OpenJPAPersistence.java:111)
> at test_test.user.UserAction.execute(UserAction.java:39)
> I've already confirmed that the OpenJPA classes in question do NOT exist in
> any other JARs in the path.
> ValidationUtils.setupValidation(ValidationUtils.java:53) calls the
> OpenJPAConfiguration.getConfigurationLog(). The object being referenced is
> JDBCConfigurationImpl, which in other classes retrieves the log reference
> perfectly fine, before it gets to the offending line.
> Seth's follow up[2]:
> After further review, using Glassfish 2.1.1 I received this error message in
> the server log:
> Caused by: java.lang.LinkageError: loader constraint violation: when
> resolving method
> "org.apache.openjpa.persistence.validation.ValidationUtils.setupValidation(Lorg/apache/openjpa/conf/OpenJPAConfiguration;)Z"
> the class loader (instance of org/apache/catalina/loader/WebappClassLoader)
> of the current class,
> org/apache/openjpa/persistence/PersistenceProviderImpl, and the class loader
> (instance of sun/misc/Launcher$AppClassLoader) for resolved class,
> org/apache/openjpa/persistence/validation/ValidationUtils, have different
> Class objects for the type org/apache/openjpa/conf/OpenJPAConfiguration used
> in the signature
> So it appears to be the WebappClassLoader and the AppClassLoader are both
> loading the OpenJPAConfiguration from the same JAR file, causing the error
> when the class is trying to be resolved in this particular method.
> [1]
> http://n2.nabble.com/Struts-2x-OpenJPA-2-0-M3-Tomcat-or-Glassfish-tp4087312p4087312.html
> [2]
> http://n2.nabble.com/Struts-2x-OpenJPA-2-0-M3-Tomcat-or-Glassfish-tp4087312p4093228.html
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