Caused by: java.lang.OutOfMemoryError: PermGen space

  at sun.misc.Unsafe.defineClass(Native Method) [rt.jar:1.7.0_45]

  at sun.reflect.ClassDefiner.defineClass(ClassDefiner.java:63) [rt.jar:1.7.0_45]

  at sun.reflect.MethodAccessorGenerator$1.run(MethodAccessorGenerator.java:399) [rt.jar:1.7.0_45]

  at sun.reflect.MethodAccessorGenerator$1.run(MethodAccessorGenerator.java:396) [rt.jar:1.7.0_45]

  at java.security.AccessController.doPrivileged(Native Method) [rt.jar:1.7.0_45]

  at sun.reflect.MethodAccessorGenerator.generate(MethodAccessorGenerator.java:395) [rt.jar:1.7.0_45]

  at sun.reflect.MethodAccessorGenerator.generateSerializationConstructor(MethodAccessorGenerator.java:113) [rt.jar:1.7.0_45]

  at sun.reflect.ReflectionFactory.newConstructorForSerialization(ReflectionFactory.java:331) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass.getSerializableConstructor(ObjectStreamClass.java:1376) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass.access$1500(ObjectStreamClass.java:72) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:493) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass$2.run(ObjectStreamClass.java:468) [rt.jar:1.7.0_45]

  at java.security.AccessController.doPrivileged(Native Method) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass.<init>(ObjectStreamClass.java:468) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass.lookup(ObjectStreamClass.java:365) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:602) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1622) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1517) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1990) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1915) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1798) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370) [rt.jar:1.7.0_45]

  at java.util.HashMap.readObject(HashMap.java:1184) [rt.jar:1.7.0_45]

  at sun.reflect.GeneratedMethodAccessor2590.invoke(Unknown Source) [:1.7.0_45]

  at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_45]

  at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_45]

  at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1017) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1893) [rt.jar:1.7.0_45]

  at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1798) [rt.jar:1.7.0_45]

What may be the reason for this error and right method to fix this? I found this in WildFly-8.2 after some tuning and enabling caching. It's runtime is Java 7. Is it better to upgrade to Java 8?