Issue with self reference on ManyToOne relationship

Question

Hi,
I have a scenario where one of the columns on a table refers to the ID of the same table for a @ManyToOne relationship. Here is an example class below to better explain the situation:
@Entity
@Table(name = "DEPARTMENT")
public class Department implements java.io.Serializable
@Id
private int ID;
@ManyToOne(targetEntity = Department.class, fetch = FetchType.EAGER)
@JoinColumn(name = "PARENT_ID")
private Department parent;
@OneToMany(mappedBy = "parent", targetEntity = Department.class, fetch = FetchType.LAZY)
private Set<Category> children = new HashSet<Category>(0);
Here if you notice the parent is the ID of another Department. When I use this during a create it seems to be trying to update the ID of an existing Department record, which is causing an exception as follows:
SEVERE: Error processing request from 127.0.0.1 for <anon>: javax.persistence.RollbackException: Exception [TOPLINK-7251] (Oracle TopLink Essentials - 2.0 (Build b41d-beta2 (04/24/2007))): oracle.toplink.essentials.exceptions.ValidationException
Exception Description: The attribute [ID] of class [Department] is mapped to a primary key column in the database. Updates are not allowed.
Any thoughts on what I might be doing wrong. Appreciate your help.
Thanks,
Sharanya

Answer 1

Thanks for the help.
It turns out the problem was related to executing a SELECT query on the entities prior to committing the transaction. Essentially, there were entities which were being created and persisted (but not committed), and these records were being retrieved via a SELECT query. At the point the query was executed, an attempt was made to flush, and since the record hadn’t been updated in the persistence context, TopLink saw the SELECT query execution as an update and thus threw the exception.
/* simplified for brevity */
@Entity
class Record {
    @Id
    @GeneratedValue(…)
    private Integer id;
    @ManyToOne(…)
    private Record parent;
    @OneToMany(…)
    private Collection<Record> children;
class RecordService {
    void addRecords(Record records…) {
        for (Record record : records) {
            addRecord(record);
    void addRecord(Record record) {
        // Execute a SELECT to get related record(s).
        // Update the record(s).
        em.persist(record);
To resolve this, I simply persist the records before executing the SELECT query, and then after the records are updated, execute a merge:
    void addRecord(Record record) {
        em.persist(record);
        // Execute a SELECT query to get related record(s).
        // Update the record(s).
        em.merge(record);
I'm not completely clear as to what point TopLink thought that the ID had been updated (it could be related to the previous post?), but this resolution seems to be working.