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From "Sahoo (JIRA)" <j...@apache.org>
Subject [jira] Updated: (FELIX-2653) LinkageError caused by duplicate class definition during implicit boot delegation
Date Tue, 12 Oct 2010 17:45:33 GMT

     [ https://issues.apache.org/jira/browse/FELIX-2653?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sahoo updated FELIX-2653:
-------------------------

    Description: 
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.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. 

  was:
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. 


Fixed the description. I had incorrectly mentioned that VM was trying to load com.acme.Foo$Factory.
Instead, VM tried to load com.acme.Foo.

> LinkageError caused by duplicate class definition during implicit boot delegation
> ---------------------------------------------------------------------------------
>
>                 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
>             Fix For: framework-3.2.0
>
>
> 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.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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