http://www.hibernate.org/116.html#A14

A PropertyAccessException often occurs when the object being passed to the setter method is of the wrong type. Check your type mappings for the offending property. (To see exactly which property was the problem, you might need to disable the CGLIB reflection optimizer.) However, the most common cause of this problem is that Hibernate attempted to assign null to a property of primitive type.

If your object has a primitive-type property mapped to a nullable database column then you will need to use a Hibernate custom type to assign a sensible default (primitive) value for the case of a null column value. A better solution is usually to use a wrapper type for the Java property.

My question is how to make a Hibernate custom type? Is it just a Java Wrapper class, such as Integer, Boolean, or something related to hibernate Nullable class?

Thanks

There is a few userType samples under the
Interceptors, userTypes and other extensions in ...

http://hibernate.org/37.html

Hope it helps.