object references an unsaved transient instance -

Question

I receive following error when I save the object using Hibernate

object references an unsaved transient instance - save the transient instance before flushing

Answer 1

I believe this might be just repeat answer, but just to clarify, I got this on a @OneToOne mapping as well as a @OneToMany. In both cases, it was the fact that the Child object I was adding to the Parent wasn't saved in the database yet. So when I added the Child to the Parent, then saved the Parent, Hibernate would toss the "object references an unsaved transient instance - save the transient instance before flushing" message when saving the Parent.

Adding in the cascade = {CascadeType.ALL} on the Parent's reference to the Child solved the problem in both cases. This saved the Child and the Parent.

Sorry for any repeat answers, just wanted to further clarify for folks.

@OneToOne(cascade = {CascadeType.ALL})
@JoinColumn(name = "performancelog_id")
public PerformanceLog getPerformanceLog() {
    return performanceLog;
}

Answer 2

This isn't the only reason for the error. I encountered it just now for a typo error in my coding, which I believe, set a value of an entity which was already saved.

X x2 = new X();
x.setXid(memberid); // Error happened here - x was a previous global entity I created earlier
Y.setX(x2);

I spotted the error by finding exactly which variable caused the error (in this case String xid). I used a catch around the whole block of code that saved the entity and printed the traces.

{
   code block that performed the operation
} catch (Exception e) {
   e.printStackTrace(); // put a break-point here and inspect the 'e'
   return ERROR;
}

Answer 3

Don't use Cascade.All until you really have to. Role and Permission have bidirectional manyToMany relation. Then the following code would work fine

    Permission p = new Permission();
    p.setName("help");
    Permission p2 = new Permission();
    p2.setName("self_info");
    p = (Permission)crudRepository.save(p); // returned p has id filled in.
    p2 = (Permission)crudRepository.save(p2); // so does p2.
    Role role = new Role();
    role.setAvailable(true);
    role.setDescription("a test role");
    role.setRole("admin");
    List<Permission> pList = new ArrayList<Permission>();
    pList.add(p);
    pList.add(p2);
    role.setPermissions(pList);
    crudRepository.save(role);

while if the object is just a "new" one, then it would throw the same error.

Answer 4

There is another possibility that can cause this error in hibernate. You may set an unsaved reference of your object A to an attached entity B and want to persist object C. Even in this case, you will get the aforementioned error.

Answer 5

Case 1: I was getting this exception when I was trying to create a parent and saving that parent reference to its child and then some other DELETE/UPDATE query(JPQL). So I just flush() the newly created entity after creating parent and after creating child using same parent reference. It Worked for me.

Case 2:

Parent class

public class Reference implements Serializable {

    @Id
    @Column(precision=20, scale=0)
    private BigInteger id;

    @Temporal(TemporalType.TIMESTAMP)
    private Date modifiedOn;

    @OneToOne(mappedBy="reference")
    private ReferenceAdditionalDetails refAddDetails;
    . 
    .
    .
}

Child Class:

public class ReferenceAdditionalDetails implements Serializable{

    private static final long serialVersionUID = 1L;

    @Id
    @OneToOne
    @JoinColumn(name="reference",referencedColumnName="id")
    private Reference reference;

    private String preferedSector1;
    private String preferedSector2;
    .
    .

}

In the above case where parent(Reference) and child(ReferenceAdditionalDetails) having OneToOne relationship and when you try to create Reference entity and then its child(ReferenceAdditionalDetails), it will give you the same exception. So to avoid the exception you have to set null for child class and then create the parent.(Sample Code)

.
.
reference.setRefAddDetails(null);
reference = referenceDao.create(reference);
entityManager.flush();
.
.

Answer 6

One possible cause of the error is the inexistence of the setting of the value of the parent entity ; for example for a department-employees relationship you have to write this in order to fix the error :

Department dept = (Department)session.load(Department.class, dept_code); // dept_code is from the jsp form which you get in the controller with @RequestParam String department
employee.setDepartment(dept);