Question

here is my code,

SiteMember class

@OneToMany(mappedBy = "member",cascade=CascadeType.ALL)
    private List<MemberThread> memberThread = new ArrayList<MemberThread>

and

MemberThread class

@ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(nullable=false)
    private SiteMember member;

MemberThreadJpaController class

public void destroy(Long id) throws IllegalOrphanException, NonexistentEntityException, NotSupportedException, RollbackException, HeuristicMixedException, HeuristicRollbackException, SecurityException, IllegalStateException, SystemException {
        EntityManager em = null;
        try {
            em = getEntityManager();
            ut.begin();
            MemberThread memberThread;
            try {
                memberThread = em.getReference(MemberThread.class, id);
                memberThread.getId();
            } catch (EntityNotFoundException enfe) {
                throw new NonexistentEntityException("The memberThread with id " + id + " no longer exists.", enfe);
            }
            List<String> illegalOrphanMessages = null;
            List<Reply> replysOrphanCheck = memberThread.getReplys();
            for (Reply replysOrphanCheckReply : replysOrphanCheck) {
                if (illegalOrphanMessages == null) {
                    illegalOrphanMessages = new ArrayList<String>();
                }
                illegalOrphanMessages.add("This MemberThread (" + memberThread + ") cannot be destroyed since the Reply " + replysOrphanCheckReply + " in its replys field has a non-nullable memberThread field.");
            }
            if (illegalOrphanMessages != null) {
                throw new IllegalOrphanException(illegalOrphanMessages);
            }
            SiteMember member = memberThread.getMember();
            if (member != null) {
                member.getMemberThread().remove(memberThread);
                member = em.merge(member);
            }
            em.remove(memberThread);
            ut.commit();
        } finally {
            if (em != null) {
                em.close();
            }
        }
    }

this will remove both SiteMember and MemberThread objects because MemberThread has a foreign key of SiteMember.how can i remove only MemberThread?

thanks..

Answer 1

Analysis

In your MemeberThread class you have a SiteMember with a CascadeType.ALL. CascadeType tells what kind of cascading operations to invoke when doing changes in persistent context.

From CascadeType API:

Defines the set of cascadable operations that are propagated to the
associated entity. The value cascade=ALL is equivalent to
cascade={PERSIST, MERGE, REMOVE, REFRESH, DETACH}.

Invoking em.remove(memberThread) will cascade all operations on SiteMember by removing it.

Solution

Change your cascade type for SiteMember in MemberThread class:

@ManyToOne(cascade={
    CascadeType.PERSIST, CascadeType.MERGE, 
    CascadeType.REFRESH, CascadeType.DETACH
})
@JoinColumn(nullable=false)
private SiteMember member;

Now REMOVE operation will not be cascaded.