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POEclipseLink/JPA2 ManyToOne bidirectional cascade persist issue
 

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    <p>This is similar to <a href="https://stackoverflow.com/questions/3197667/how-to-cascade-persist-using-jpa-eclipselink">How to cascade persist using JPA/EclipseLink</a></p> <p>I have to entities like so. One is RoomEntity that has a one to many bi-directional relationship with ComputerEntity. eg. each room has 0..n computers. </p> <pre><code>@Entity public class ComputerEntity implements Serializable { @Id @GeneratedValue(generator="computerSeq",strategy= GenerationType.SEQUENCE) @SequenceGenerator(name="computerSeq",sequenceName="SEQUENCECOMPUTERID",allocationSize=1) private long computerID; @Column(name = "COMPUTERID") public long getComputerID() { return computerID; } public void setComputerID(long computerID) { this.computerID = computerID; } private RoomEntity room; @ManyToOne() @JoinColumn(name = "ROOMID", referencedColumnName = "ROOMID") public RoomEntity getRoom() { return room; } public void setRoom(RoomEntity room) { this.room = room; } } //ComputerEntity @Entity public class RoomEntity { @Id @GeneratedValue(generator="roomSeq",strategy= GenerationType.SEQUENCE) @SequenceGenerator(name="roomSeq",sequenceName="SEQUENCEROOMID",allocationSize=1) private long roomID; @OneToMany(mappedBy = "room", cascade = {CascadeType.PERSIST, CascadeType.REMOVE}) private Set&lt;ComputerEntity&gt; computers; @javax.persistence.Column(name = "ROOMID") public long getRoomID() { return roomID; } public void setRoomID(long roomID) { this.roomID = roomID; } public Set&lt;ComputerEntity&gt; getComputers() { return computers; } public void setComputers(Set&lt;ComputerEntity&gt; computers) { for(ComputerEntity computer : computers) { computer.setRoom(this); } this.computers = computers; } }//RoomEntity </code></pre> <p>When I try to persist an new room with a computer like so:</p> <pre><code> RoomEntity room = new RoomEntity(); room.setAdministrator("Fox Moulder"); room.setLocation("Area 51"); ComputerEntity computer1 = new ComputerEntity(); computer1.setDescription("Alienware area51 laptop"); Set&lt;ComputerEntity&gt; computers = new HashSet&lt;ComputerEntity&gt;(); computers.add(computer1); room.setComputers(computers); roomBean.createRoom(room); </code></pre> <p>roomBean is a Stateless EJB and roomBean.createRoom simply calls entityManager.persist(room). Since I have a CascadeType.PERSIST on the computers field of RoomEntity the ComptuerEntity is created. However, if I look at the room field of that ComputerEntity I see that room field is null. I would have assumed that Eclipselink would have automatically filled in the room since I have a bi-directional relationship. In order to have the room set in this way I had to add</p> <pre><code> for(ComputerEntity computer : computers) { computer.setRoom(this); } </code></pre> <p>to room.setComputers(...). Is this the correct approach or is there a way to get Eclipselink to automatically set this? </p> <p>Thanks. -Noah</p>
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