Annotations, Enums, and our TemporaryClassLoader
------------------------------------------------
Key: OPENJPA-672
URL: https://issues.apache.org/jira/browse/OPENJPA-672
Project: OpenJPA
Issue Type: Bug
Components: lib
Affects Versions: 1.1.0, 1.0.3, 1.0.2, 1.0.1, 1.0.0
Reporter: Kevin Sutter
Assignee: Kevin Sutter
I thought I had opened a JIRA for this dev forum discussion
(http://n2.nabble.com/Sun-JDK-problem-with-duplicate-annotations-tt218302.html#a218302),
but I guess not.
I have been tracking this problem via a problem report with the IBM JDK team
(since I was able to eventually reproduce the same problem with both the Sun
JDK and IBM JDK). So far, we have not determined a definite problem with the
JDK processing of annotations and enums.
Here's a summary of the basic problem (from the dev forum post):
The scenario is that I have annotations doubly defined (ie.
javax.persistence.OneToMany and alt.persistence.OneToMany). A single entity
might utilize both of them, like this:
@javax.persistence.OneToMany(cascade=javax.persistence.CascadeType.REMOVE)
@alt.persistence.OneToMany(cascade=alt.persistence.CascadeType.REMOVE)
Collection<Fill> buySideFills;
This results in the following callstack snippet when running with the
-javaagent version of enhancement and the Sun JDK (fixpack 15):
java.lang.ArrayStoreException:
sun.reflect.annotation.AnnotationTypeMismatchExceptionProxy
at
sun.reflect.annotation.AnnotationParser.parseEnumArray(AnnotationParser.java:673)
at
sun.reflect.annotation.AnnotationParser.parseArray(AnnotationParser.java:462)
at
sun.reflect.annotation.AnnotationParser.parseMemberValue(AnnotationParser.java:286)
at
sun.reflect.annotation.AnnotationParser.parseAnnotation(AnnotationParser.java:222)
at
sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:69)
at
sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:52)
at java.lang.reflect.Field.declaredAnnotations(Field.java:1002)
at java.lang.reflect.Field.getDeclaredAnnotations(Field.java:995)
at
java.lang.reflect.AccessibleObject.getAnnotations(AccessibleObject.java:179)
at
org.apache.openjpa.lib.util.J2DoPriv5Helper$1.run(J2DoPriv5Helper.java:51)
at java.security.AccessController.doPrivileged(Native Method)
at
org.apache.openjpa.persistence.PersistenceMetaDataDefaults.annotated(PersistenceMetaDataDefaults.java:293)
at
org.apache.openjpa.persistence.PersistenceMetaDataDefaults.getAccessType(PersistenceMetaDataDefaults.java:262)
at
org.apache.openjpa.persistence.PersistenceMetaDataDefaults.getAccessType(PersistenceMetaDataDefaults.java:250)
at
org.apache.openjpa.meta.AbstractMetaDataDefaults.populate(AbstractMetaDataDefaults.java:155)
at
org.apache.openjpa.persistence.PersistenceMetaDataDefaults.populate(PersistenceMetaDataDefaults.java:227)
at
org.apache.openjpa.meta.MetaDataRepository.addMetaData(MetaDataRepository.java:794)
at
org.apache.openjpa.meta.MetaDataRepository.addMetaData(MetaDataRepository.java:780)
at
org.apache.openjpa.persistence.AnnotationPersistenceMetaDataParser.getMetaData(AnnotationPersistenceMetaDataParser.java:657)
at
org.apache.openjpa.persistence.AnnotationPersistenceMetaDataParser.parseClassAnnotations(AnnotationPersistenceMetaDataParser.java:480)
at
org.apache.openjpa.persistence.AnnotationPersistenceMetaDataParser.parse(AnnotationPersistenceMetaDataParser.java:352)
at
org.apache.openjpa.persistence.PersistenceMetaDataFactory.load(PersistenceMetaDataFactory.java:229)
at
org.apache.openjpa.meta.MetaDataRepository.getMetaDataInternal(MetaDataRepository.java:474)
at
org.apache.openjpa.meta.MetaDataRepository.getMetaData(MetaDataRepository.java:294)
at org.apache.openjpa.enhance.PCEnhancer.<init>(PCEnhancer.java:248)
at org.apache.openjpa.enhance.PCEnhancer.<init>(PCEnhancer.java:219)
at
org.apache.openjpa.enhance.PCClassFileTransformer.transform0(PCClassFileTransformer.java:139)
at
org.apache.openjpa.enhance.PCClassFileTransformer.transform(PCClassFileTransformer.java:120)
at sun.instrument.TransformerManager.transform(TransformerManager.java:122)
at
sun.instrument.InstrumentationImpl.transform(InstrumentationImpl.java:155)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
at java.net.URLClassLoader.access$100(URLClassLoader.java:56)
at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:242)
at
org.apache.openjpa.meta.MetaDataRepository.classForName(MetaDataRepository.java:1298)
at
org.apache.openjpa.meta.MetaDataRepository.loadPersistentTypes(MetaDataRepository.java:1280)
at
org.apache.openjpa.jdbc.kernel.JDBCBrokerFactory.synchronizeMappings(JDBCBrokerFactory.java:138)
at
org.apache.openjpa.jdbc.kernel.JDBCBrokerFactory.newBrokerImpl(JDBCBrokerFactory.java:119)
at
org.apache.openjpa.kernel.AbstractBrokerFactory.newBroker(AbstractBrokerFactory.java:189)
at
org.apache.openjpa.kernel.DelegatingBrokerFactory.newBroker(DelegatingBrokerFactory.java:142)
at
org.apache.openjpa.persistence.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:192)
at
org.apache.openjpa.persistence.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:145)
at
org.apache.openjpa.persistence.EntityManagerFactoryImpl.createEntityManager(EntityManagerFactoryImpl.java:1)
>From working with the JDK team, the problem is surfacing because the
>ClassLoader (AppClassLoader) that is used to load the Enum type when the
>alt.persistence.OneToMany is loaded is not the same ClassLoader
>(TemporaryClassLoader) when the Enum type is loaded by our enhancement
>processing. Thus, the AnnotationTypeMismatchExceptionProxy from the JDK.
One way to workaround the problem is to add a test for Enum types in the
TemporaryClassLoader and use the AppClassLoader in this case (much like we do
for Annotation types):
if (isAnnotation(classBytes) || isEnum(classBytes))
return Class.forName(name, resolve,
getClass().getClassLoader());
The JDK team suggested removing the check for isAnnotation (and isEnum)
altogether since that resolved the simple testcase that I had put together for
their benefit. Unfortunately, that doesn't work for our enhancement processing
for a couple of reasons. The _strats structure in PersistentMetaDataDefaults
depended on the org.apache.openjpa.persistence.PersistentCollection class. By
removing the conditional above, then we had a mismatch in classloaders for this
data structure, much like the jdk problem.
I tried changing the key for this _strats structure to use the class name
string instead of the actual class instance. This got us around our immediate
concern, but eventually I hit another JDK issue with mismatched classloaders
when processing the annotations in AnnotationPersistentMetaDataParser:
parsePersistentCollection(fmd, (PersistentCollection)
el.getAnnotation(PersistentCollection.class));
The loading of this PersistentCollection.class used the AppClassLoader, so the
lookup via getAnnotation didn't find anything since the original annotation was
loaded by the TemporaryClassLoader. Trying to get around this situation was
creating some pretty ugly code.
So, I am leaning towards the original workaround as a "solution" with proper
commenting. By allowing the AppClassLoader to load enum types (vs the
TemporaryClassLoader), we would "pollute" the AppClassLoader with left over
enum classes. This would seem to be a minor drawback. Of course, if we ever
need to allow for the enhancement of enum classes, then we're up a creek...
Enough detail for now. Comments and suggestions are welcome.
Kevin
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