org.hibernate.HibernateException: Javassist Enhancement failed

Exception in thread "main" org.hibernate.HibernateException: Javassist Enhancement failed: model.User
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.getProxy(JavassistLazyInitializer.java:142)
at org.hibernate.proxy.pojo.javassist.JavassistProxyFactory.getProxy(JavassistProxyFactory.java:71)
at org.hibernate.tuple.entity.AbstractEntityTuplizer.createProxy(AbstractEntityTuplizer.java:631)
at org.hibernate.persister.entity.AbstractEntityPersister.createProxy(AbstractEntityPersister.java:3736)
at org.hibernate.event.def.DefaultLoadEventListener.createProxyIfNecessary(DefaultLoadEventListener.java:360)
at org.hibernate.event.def.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:281)
at org.hibernate.event.def.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:152)
at org.hibernate.impl.SessionImpl.fireLoad(SessionImpl.java:1090)
at org.hibernate.impl.SessionImpl.internalLoad(SessionImpl.java:1038)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:630)
at org.hibernate.type.EntityType.resolve(EntityType.java:438)
at org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:139)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:982)
at org.hibernate.loader.Loader.doQuery(Loader.java:857)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:274)
at org.hibernate.loader.Loader.loadCollection(Loader.java:2166)
at org.hibernate.loader.collection.CollectionLoader.initialize(CollectionLoader.java:62)
at org.hibernate.persister.collection.AbstractCollectionPersister.initialize(AbstractCollectionPersister.java:627)
at org.hibernate.event.def.DefaultInitializeCollectionEventListener.onInitializeCollection(DefaultInitializeCollectionEventListener.java:83)
at org.hibernate.impl.SessionImpl.initializeCollection(SessionImpl.java:1863)
at org.hibernate.collection.AbstractPersistentCollection.initialize(AbstractPersistentCollection.java:369)
at org.hibernate.collection.AbstractPersistentCollection.read(AbstractPersistentCollection.java:111)
at org.hibernate.collection.PersistentSet.iterator(PersistentSet.java:186)
at main.TestAd.displayData(TestAd.java:49)
at main.TestAd.main(TestAd.java:35)
Caused by: java.lang.InstantiationException: model.User_$$_javassist_2
at java.lang.Class.newInstance0(Unknown Source)
at java.lang.Class.newInstance(Unknown Source)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.getProxy(JavassistLazyInitializer.java:139)
... 24 more

Issue:

Hibernate is not able to instantiate the model User using java assist.


Solution:

Create a default no-arg constructor to the class User