Question

We are using Hibernate Envers and have the following situation:

A class BusinessObjectType and a class Identity with a reference to BusinessObjectType:

@Entity
@Table( name = "ID_IDENTITY" )
@Audited
public class Identity {

    @ManyToOne
    @JoinColumn( name = "BO_TYPE_ID" )
    @IndexColumn( name = "INDEX_BO_BO_TYPE" )
    private BusinessObjectType businessObjectType;

    […]

}

We then query for all the version of Identity with:

AuditQuery auditQuery = auditReader.createQuery().forRevisionsOfEntity(
    Identity.class,
    false,
    true );
auditQuery.add( AuditEntity.id().eq( dbid ) );

@SuppressWarnings( "unchecked" )
List< Object[]> history = (List< Object[]>) auditQuery.getResultList();

If the stored identity does not have a BusinessObjectType (i.e., businessObjectType is and was null) everything works like a charm.

If the identity had a businessObjectType != null we get a “Javassist Enhancement failed” Exception:

Javassist Enhancement failed: ch.ethz.id.wai.baseclasses.BusinessObjectType

The error seems to be related to Envers trying to instantiate a BusinessObjectType but I don’t really see what the problem could be (Hibernate has no problems with both objects if we don’t use an AuditQuery).

The cause of the exception is

java.lang.InstantiationException: ch.ethz.id.wai.baseclasses.BusinessObjectType_$$_javassist_49

with no stack trace.

Any hint on what the problem could be?

Answer 1

This happens inside the following class JavassistLazyInitializer A Javassist-based lazy initializer proxy.

Without having a look at full source it is difficult to comment but you can try following options.

• Turn off Lazy loading for @ManyToOne relationship [This is a design decision so watch out if it doesn’t fit in overall solution]
• Provide a default public constructor for your entity which is causing problem[This is easier]
• turn off reflection optimisation if not really required by setting up hibernate.bytecode.use_reflection_optimizer property to false

Let us know if this helps