LinkageError caused by duplicate class definition during implicit boot
delegation
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Key: FELIX-2653
URL: https://issues.apache.org/jira/browse/FELIX-2653
Project: Felix
Issue Type: Bug
Components: Framework
Affects Versions: framework-3.0.4
Environment: java version "1.6.0_21"
Java(TM) SE Runtime Environment (build 1.6.0_21-b06)
Java HotSpot(TM) Server VM (build 17.0-b16, mixed mode)
Reporter: Sahoo
Priority: Critical
I am seeing linkage errors caused by attempt to load duplicate classes and I
think it is caused by implicit boot delegation. In our server log, we see the
following exception stack:
java.lang.LinkageError: loader (instance of java/net/URLClassLoader):
attempted duplicate class definition for name: "com/acme/Foo"
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClassCond(ClassLoader.java:632)
at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
at
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
at java.net.URLClassLoader.access$000(URLClassLoader.java:58)
at java.net.URLClassLoader$1.run(URLClassLoader.java:197)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
at com.acme.Foo$Factory.createRequest(Foo.java:93)
I tried to trace the execution to find out what causes the class to be defined
for the first time and with the help of btrace
(http://projectkenai.com/projects/btrace/), I could obtain the stack and
relevant information. First time the class is defined, the stack looks like
this:
java.security.SecureClassLoader.defineClass(SecureClassLoader.java:141)
java.net.URLClassLoader.defineClass(URLClassLoader.java:283)
java.net.URLClassLoader.access$000(URLClassLoader.java:58)
java.net.URLClassLoader$1.run(URLClassLoader.java:197)
java.security.AccessController.doPrivileged(Native Method)
java.net.URLClassLoader.findClass(URLClassLoader.java:190)
java.lang.ClassLoader.loadClass(ClassLoader.java:307)
java.lang.ClassLoader.loadClass(ClassLoader.java:248)
org.apache.felix.framework.ModuleImpl.getEnclosingClass(ModuleImpl.java:1570)
org.apache.felix.framework.ModuleImpl.isClassNotLoadedFromBundle(ModuleImpl.java:1545)
org.apache.felix.framework.ModuleImpl.doImplicitBootDelegation(ModuleImpl.java:1498)
org.apache.felix.framework.ModuleImpl.searchDynamicImports(ModuleImpl.java:1452)
org.apache.felix.framework.ModuleImpl.findClassOrResourceByDelegation(ModuleImpl.java:727)
org.apache.felix.framework.ModuleImpl.access$300(ModuleImpl.java:73)
org.apache.felix.framework.ModuleImpl$ModuleClassLoader.loadClass(ModuleImpl.java:1733)
java.lang.ClassLoader.loadClass(ClassLoader.java:248)
org.apache.felix.framework.ModuleImpl.getClassByDelegation(ModuleImpl.java:638)
org.apache.felix.framework.Felix.loadBundleClass(Felix.java:1599)
org.apache.felix.framework.BundleImpl.loadClass(BundleImpl.java:904)
org.jvnet.hk2.osgiadapter.OSGiModuleImpl$3$1.run(OSGiModuleImpl.java:399)
java.security.AccessController.doPrivileged(Native Method)
org.jvnet.hk2.osgiadapter.OSGiModuleImpl$3.loadClass(OSGiModuleImpl.java:395)
java.lang.ClassLoader.loadClass(ClassLoader.java:248)
com.sun.enterprise.v3.server.APIClassLoaderServiceImpl$APIClassLoader.loadClass(APIClassLoaderServiceImpl.java:169)
java.lang.ClassLoader.loadClass(ClassLoader.java:296)
java.lang.ClassLoader.loadClass(ClassLoader.java:248)
com.acme.Foo$Factory.bar(Foo.java:93)
As you can see, when bar method is called, VM tries to load
com.acme.Foo$Factory.class and the call reaches
org.apache.felix.framework.ModuleImpl.getEnclosingClass. getEnclosingClass
actually causes the enclosing class, com.acme.Foo, to be defined. So, VM
actually records this new class in loaded classes cache of the appropriate
loader, but Felix does not consult the loaded classes cache again before trying
to define the class.
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