Is there any way to find out all the dirty objects of a given session?

I dont think that hibernate provide direct method to find dirty objects, however you may do this by extending EmptyInterceptor. something like this.

public class myAuditLogInterceptor extends EmptyInterceptor{
private Set dirtyAuditables = new HashSet();
public boolean onFlushDirty(Object entity,
Serializable id,
Object[] currentState,
Object[] previousState,
String[] propertyNames,
Type[] types) throws CallbackException {

dirtyAuditables .add(entity);
return false;
}

}

the size of the dirtyAuditable will tell you the no of dirty objects that are found in a particular session.