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PONullPointerException when accessing lazy loaded collection within DAO method
 

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    <p>I'm having a strange issue with Spring and Hibernate when running multiple threads in an application. I'm using spring 3.2.0.RELEASE and hibernate 4.1.12.Final. The issue is that for some objects, when they are retrieved from the db, the retrieval succeeds, but all mapped collections are not being set. Here's an example of my repo:</p> <pre><code>@Repository("fooRepository") public class FooRepository { private static final Logger log = Logger.getLogger(FooRepository.class); @Autowired private SessionFactory sessionFactory; @Override @Transactional public Foo retrieve(final Long id) { Foo instance = (Foo) sessionFactory.getCurrentSession().get(Foo.class, id); for (CollectionMember member : instance.getCollectionMembers()) { log.debug(member.getId()); } return instance; } </code></pre> <p>For some objects, this method always throws the following error when trying to access the CollectionMember list:</p> <pre><code>Caused by: java.lang.NullPointerException at org.hibernate.collection.internal.PersistentBag.toString(PersistentBag.java:501) </code></pre> <p>The problem is that the session.get() call creates PersistentBag objects for all lazy loaded collections but never sets the content. This only occurs when multithreading is enabled. Can anybody explain why this is happening?</p> <p>EDIT: Here's the relevant bit of the foo class:</p> <pre><code>@Entity @Table(name = "FOO") @XmlRootElement(name = "foo") public class Foo { @EmbeddedId private FooPK id; @OneToMany @NotFound(action = NotFoundAction.IGNORE) @JoinColumns({ @JoinColumn(name = "COLLECTION_ID", referencedColumnName = "COLLECTION_ID"), @JoinColumn(name = "FOO_ID", referencedColumnName = "FOO_ID")}) private List&lt;CollectionMember&gt; collectionMembers = new ArrayList&lt;CollectionMember&gt;(); </code></pre> <p>And the CollectionMember class:</p> <pre><code>@Entity @Table(name = "COLLECTION_MEMBER") @XmlRootElement(name = "collectionMember") public class CollectionMember { @EmbeddedId private CollectionMemberPK primaryKey; @ManyToOne @JoinColumn(name = "COLL_CODE") private CollectionCode collectionCode; </code></pre>
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    1. USRockenstein
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    1. COProviding full stack trace (even if its a bit verbose) might help troubleshoot the problem better.
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    2. COany chance you can post the Foo and CollectionMember classes, or at least the bits that show mapping annotations (or the hbm.xml if you are using xml config)
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      1. USGareth Davis
    3. COI can't post the full stacktrace unless I go through and manually change a bunch of package names so you can't tell where it came from. If you really think the full stacktrace would provide more info I'll do it, but I'm not convinced you'd need any more than you've already got in that sense, I'll add the mappings though.
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