I have ManyToMany relation between Student and Course.

class Student {

@ManyToMany(....)
public List<Course> getCourses() { ...}
public void setCourses(List<Course> courses) {...}

}

After modifying the course collection of a student, and then update the student, I got the following exception:

javax.ejb.EJBTransactionRolledbackException: java.lang.IllegalStateException: org.hibernate.
TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: pacakge.Course

The student and courses have already been persisted in database before updating the student. What is the possible reasons for the error?

Thanks! Dave

Can you post some more code like what your doing before the error occurs, do you have a JUnit test to replicate it? Also the full stack trace would be nice...

Hi ,

What i can think of without the code is that maybe you missed the cascade option in the student class.


Try this with your collection
@Cascade({org.hibernate.annotations.CascadeType.SAVE_UPDATE,
org.hibernate.annotations.CascadeType.DELETE_ORPHAN})

Thanks!
I am using JBoss 4.0.5GA, The CascadeType does not have SAVE_UPDATE or DELETE_ORPHAN.

If I retrieve a list of courses from database and assign them to a student , and then save(merge) the student, all in one transaction, it works fine, no errors.

The issue occurs when I work on detached entities, because of the nature of web application.

Transaction 1: get the student from database
Transaction 2: get all available courses from database
Transaction 3: let user select a number of courses (no db operation)
student.setCourses(selectedCourses);
Transaction 4: merge the student. --- error occurs.
em.merge(student)


Thanks for ideas.

It is @ManyToMany relation. Changing students should not change courses. MERGE/SAVE_UPDATE cascade will change courses. correct? Thanks.