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POJPA: Merge @OneToMany Duplicate entry error
 

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  1. POJPA: Merge @OneToMany Duplicate entry error
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    <p>I'm alwways getting the following error:</p> <pre><code>Internal Exception: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry '2-1' for key 'PRIMARY' Error Code: 1062 Call: INSERT INTO ENTITY_ENTITY (relationships_ID, Entity_ID) VALUES (?, ?) bind =&gt; [1, 2] Query: DataModifyQuery(sql="INSERT INTO ENTITY_ENTITY (relationships_ID, Entity_ID) VALUES (?, ?)") </code></pre> <p>My classes look like:</p> <pre><code>@javax.persistence.Entity public class Entity { @Id @GeneratedValue(strategy = GenerationType.TABLE) protected Long id; @Column(nullable=false, updatable=false) protected String name; @OneToMany(cascade=CascadeType.MERGE) protected Collection&lt;Entity&gt; relationships = new ArrayList&lt;Entity&gt;(); } </code></pre> <p>One instance of this class can reference other instances of the same type (self-referencing). Now, while creating one instance which references another, everything works fine. But the problem is, when such an (detached - I'm not quite sure, because the instance is edited via a Facelets form) instance is updated, i.e. the name, then by executing the EntityManager merge operation the exception - as mentioned above - is thrown.</p> <p><strong>EDIT:</strong><br> 1. Create one instance of Entity (i.e. E1).<br> 2. Persist E1 via em.persist(E1).<br> 3. Later, create another instance of Entity (E2) which refreneces E1 via the property <em>relationships</em>.<br> 4. And persist E2: em.persist(E2).</p> <p>--- Until now everything works fine. </p> <ol start="5"> <li>Load to browse all persisted Entity instances and choose E2 for editing (via a Web interface Facelet).</li> <li>Change i.e. the name of E2. </li> <li>To save the changes: Call em.merge(E2). </li> </ol> <p>---Now the Exception is thrown!</p> <p><strong>END EDIT</strong></p> <p>What's wrong with my code? Please, help me!!!</p>
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    1. USgerry
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    1. COCan you show some (pseudo) code for the whole flow and fix the mapping (or the title)?
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      1. POJPA: Merge @OneToMany Duplicate entry error
      1. USPascal Thivent
 

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