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POHibernate JPA - ManyToOne relationship not populated
 

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  1. POHibernate JPA - ManyToOne relationship not populated
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    <p>I'm currently moving a (working) app from using EclipseLink to Hibernate JPA, mostly it's gone quite smoothly, but I'm finding one thing that I can't explain, and also can't think of any good search terms!</p> <p>Basically, I have four entities, with one-to-many relationships forming a chain:</p> <p>EntityA has a list of EntityB's, each of which has a list of EntityC's, each of which have a list of EntityD's</p> <p>each of those then has a many-to-one relationship going the other way, so:</p> <p>EntityD has an EntityC, which has an EntityB, which has an EntityA.</p> <p>That is (heavily reduced for clarity):</p> <pre><code>@Entity public class EntityA { @OneToMany (cascade = CascadeType.All, mappedBy = "entityA") private List&lt;EntityB&gt; entityBList; ... } @Entity public class EntityB { @OneToMany (cascade = CascadeType.All, mappedBy = "entityB") private List&lt;EntityC&gt; entityCList; @JoinColumn (name = "ENTITY_A", referencedColumnName = "ENTITY_A_ID") @ManyToOne (cascade = CascadeType.PERSIST, optional = false) private EntityA entityA; } @Entity public class EntityC { @OneToMany (cascade = CascadeType.ALL, mappedBy = "entityC") private List&lt;EntityD&gt; entityDList; @JoinColumn (name = "ENTITY_B", referencedColumnName = "ENTITY_B_ID") @ManyToOne (cascade = CascadeType.PERSIST, optional = false) private EntityB entityB; } @Entity public class EntityD { @JoinColumn (name = "ENTITY_C", referencedColumnName = "ENTITY_C_ID") @ManyToOne (cascade = CascadeType.PERSIST, optional = false) private EntityC entityC; } </code></pre> <p>I get an EntityA from the database (looking it up by its primary key), and thus get a nicely populated EntityA instance, with a PersistentBag for my <code>List&lt;EntityB&gt;</code>. I see a lazy load happening when I dereference that <code>List&lt;EntityB&gt;</code>, and the same repeated for getting EntityCs from EntityB.</p> <p>At this point, everything is as I expect, I have an EntityA, B and C all fully populated with the values from the database, but then I try to get my EntityD, from EntityC, and find that it's null.</p> <p>My entity manager is still open and active at this point, and even if I look at it in the debugger immediately after getting the EntityA, I can walk through the relationships, as far as EntityC, and again see the 'entityDList' as null.</p> <p>The only solution I've found so far is to use:</p> <pre><code>EntityManager.refresh(entityC); </code></pre> <p>which populates all its elements including a lazily-loaded PersistentBag for the entityDList.</p> <p>So, my guess is that Hibernate is only populating the references 2 levels deep (or 3, depending on how you count), and giving up after that, although I don't really understand why that would be. Does that make sense to anyone?</p> <p>Is there any solution other than the .refresh? Some kind of config or annotation value that will make Hibernate populate the references all the way down?</p>
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