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POTwo almost identical OneToOne in Entity, custom join annotation
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  1. POTwo almost identical OneToOne in Entity, custom join annotation
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    copied!<p>I've got Parent - Child relationship OneToOne, but two of them. Annotations are not good but it produces good DB schema, yet code is not working. If I try to save Parent instance, Hibernate at first tries to save child1 and child2 - but it breaks FK defined in Child -> because owner doesn't exist yet in DB...So I need to save Parent and then child1, and child2.</p> <p>If I could do that it doesn't help, because when I try to load Parent, Hibernate will not know which record in Child table belongs to child1 or child2...So in this case I would need to specify one condition in join for child1 something like "where type = 1" and for child2 "where type = 2"...</p> <p>Just to clarify: in <code>Child</code> table there will be zero or one child for one <code>Parent</code> with <code>ChildType.A</code> (always child1) and zero or one child with <code>ChildType.B</code> (always child2).</p> <p>I need to save xml which looks like this:</p> <pre><code>&lt;parent id="" oid=""&gt; &lt;child1 (and other attributes)&gt; &lt;child2 (and other attributes)&gt; &lt;parent&gt; </code></pre> <p>Both <code>child1</code> and <code>child2</code> elements are the same type therefore are type of <code>Child</code> in java classes. Only difference is element name (in java I differentiate them with <code>ChildType</code>). Only identification for children are <code>id</code> and <code>oid</code> attributes from parent. They points to another <code>Parent</code> hence <code>target</code> in <code>Child</code>. </p> <p>I need to change annotations somehow to get this working...Do you guys have some ideas, because I'm really stuck???</p> <p>Parent.java</p> <pre><code>public class Parent { private String oid private Long id; private Child child1; private Child child2; @Id @GeneratedValue(generator = "IdGenerator") @GenericGenerator(name = "IdGenerator", strategy = "com.example.IdGenerator") @Column(name = "id") public Long getId() { return id; } @Id @GeneratedValue(generator = "OidGenerator") @GenericGenerator(name = "OidGenerator", strategy = "com.example.OidGenerator") @Column(name = "oid", nullable = false, updatable = false, length = 36) public String getOid() { return oid; } @OneToOne(optional = true, fetch = FetchType.EAGER) @Cascade({org.hibernate.annotations.CascadeType.ALL}) public Child getChild1() { return child1; } @OneToOne(optional = true, fetch = FetchType.EAGER) @Cascade({org.hibernate.annotations.CascadeType.ALL}) public Child getChild2() { return child2; } } </code></pre> <p>Child.java</p> <pre><code>public class Child { private Parent owner; private String ownerOid; private Long ownerId; private ChildType type; private Parent target; @MapsId("owner") @ManyToOne(fetch = FetchType.LAZY) @PrimaryKeyJoinColumns({ @PrimaryKeyJoinColumn(name = "owner_oid", referencedColumnName = "oid"), @PrimaryKeyJoinColumn(name = "owner_id", referencedColumnName = "id") }) public Parent getOwner() { return owner; } @MapsId("target") @ManyToOne(fetch = FetchType.LAZY) @PrimaryKeyJoinColumns({ @PrimaryKeyJoinColumn(name = "target_oid", referencedColumnName = "oid"), @PrimaryKeyJoinColumn(name = "target_id", referencedColumnName = "id") }) public Parent getTarget() { return target; } @Id @Column(name = "owner_id") public Long getOwnerId() { if (ownerId == null &amp;&amp; owner != null) { ownerId = owner.getId(); } return ownerId; } @Id @Column(name = "owner_oid", length = 36) public String getOwnerOid() { if (ownerOid == null &amp;&amp; owner != null) { ownerOid = owner.getOid(); } return ownerOid; } @Id @Column(name = "target_id") public Long getTargetId() { if (targetId == null &amp;&amp; target != null) { targetId = target.getId(); } return targetId; } @Id @Column(name = "target_oid", length = 36) public String getTargetOid() { if (targetOid == null &amp;&amp; target != null) { targetOid = target.getOid(); } if (targetOid == null) { targetOid = ""; } return targetOid; } @Id @Enumerated(EnumType.ORDINAL) public ChildType getType() { if (type == null) { return ChildType.A; } return type; } } </code></pre> <p>ChildType.java</p> <pre><code>public enum ChildType { A, B; } </code></pre> <p>I also tried to use <code>mappedBy</code> approach <a href="https://stackoverflow.com/questions/9676649/onetoone-custom-join-query">mappedBy approach</a> but there are still problems with loading - I can't tell hibernate which child record belogs to which child class member variable.</p>
 

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