I just ran into an interesting exception within a Java project. I implemented a couple of Java classes along with hibernate mapping files. Until today, everything worked just fine. I then added some attributes/properties to a class and completed the mapping file. After deploying and testing the application I ran into the following hibernate exception: org.hibernate.HibernateException: Unable to instantiate default tuplizer [org.hibernate.tuple.entity.PojoEntityTuplizer] I really couldn’t figure out what was wrong and tried almost everything.