I tried to reproduce the case. Once I added the jax-b runtime maven dependency, I've got this exception:

Caused by: java.lang.NullPointerException
at javassist.util.proxy.SecurityActions.setAccessible (SecurityActions.java:103)
at javassist.util.proxy.DefineClassHelper.toClass3 (DefineClassHelper.java:151)
at javassist.util.proxy.DefineClassHelper.toClass2 (DefineClassHelper.java:134)
at javassist.util.proxy.DefineClassHelper.toClass (DefineClassHelper.java:95)
at javassist.util.proxy.FactoryHelper.toClass (FactoryHelper.java:131)
at javassist.util.proxy.ProxyFactory.createClass3 (ProxyFactory.java:530)
at javassist.util.proxy.ProxyFactory.createClass2 (ProxyFactory.java:515)
at javassist.util.proxy.ProxyFactory.createClass1 (ProxyFactory.java:451)
at javassist.util.proxy.ProxyFactory.createClass (ProxyFactory.java:422)
at org.hibernate.proxy.pojo.javassist.JavassistProxyFactory.postInstantiate (JavassistProxyFactory.java:75)
at org.hibernate.tuple.entity.PojoEntityTuplizer.buildProxyFactory (PojoEntityTuplizer.java:162)
at org.hibernate.tuple.entity.AbstractEntityTuplizer.<init> (AbstractEntityTuplizer.java:156)
at org.hibernate.tuple.entity.PojoEntityTuplizer.<init> (PojoEntityTuplizer.java:58)

Halil, could you confirm that is the one you have too? Thanks