class org.apache.openjpa.util.java$util$Collections$SingletonSet$0$proxy cannot access its superclass java.util.Collections$SingletonSet

[Christian Defoy]

Hello!

I am getting a strange message when merging an entity.  My entity
contains a set of objects of class A.  Each of these objects, in turn,
have an attribute that is a set.  My entity gets detached, then a
bunch of As get added and every A contains a set.  Most of the As will
contain a singleton but still some may contain a regular set.

The error message is quite clear.  OpenJPA can't access the superclass
because the superclass is private static inside java.util.Collections.

java.lang.IllegalAccessError: class
org.apache.openjpa.util.java$util$Collections$SingletonSet$0$proxy
cannot access its superclass java.util.Collections$SingletonSet
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:465)
        at serp.bytecode.BCClassLoader.findClass(BCClassLoader.java:73)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
        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.util.ProxyManagerImpl.loadProxy(ProxyManagerImpl.java:479)
        at 
org.apache.openjpa.util.ProxyManagerImpl.getFactoryProxyCollection(ProxyManagerImpl.java:365)
        at 
org.apache.openjpa.util.ProxyManagerImpl.copyCollection(ProxyManagerImpl.java:185)
        at 
org.apache.openjpa.kernel.AttachStrategy.copyCollection(AttachStrategy.java:341)
        at 
org.apache.openjpa.kernel.AttachStrategy.attachCollection(AttachStrategy.java:318)
        at 
org.apache.openjpa.kernel.AttachStrategy.attachField(AttachStrategy.java:217)
        at 
org.apache.openjpa.kernel.VersionAttachStrategy.attach(VersionAttachStrategy.java:134)
        at 
org.apache.openjpa.kernel.AttachManager.attach(AttachManager.java:239)
        at 
org.apache.openjpa.kernel.AttachStrategy.attachCollection(AttachStrategy.java:330)
        at 
org.apache.openjpa.kernel.DetachedStateManager.attach(DetachedStateManager.java:249)
        at 
org.apache.openjpa.kernel.AttachManager.attach(AttachManager.java:239)
        at 
org.apache.openjpa.kernel.AttachManager.attach(AttachManager.java:100)
        at org.apache.openjpa.kernel.BrokerImpl.attach(BrokerImpl.java:3139)
        at 
org.apache.openjpa.kernel.DelegatingBroker.attach(DelegatingBroker.java:1147)
        at 
org.apache.openjpa.persistence.EntityManagerImpl.merge(EntityManagerImpl.java:665)


My question is: should I avoid using singleton set?  I guess it is the
same kind of issue as with the EnumSet...

Thanks in advance!

Christian