Why am I getting this NullPointer exception?

Question

Two tables, primary key of one is foreign key of another (Legacy DB)
I used bi-directional one to one mapping:

@Entity
public class First {
    @Id protected int a;

    @OneToOne(mappedBy ="first", cascade = CascadeType.PERSIST)
    @JoinColumn(name = "a")
    protected Second second;
}


@Entity
public class Second {

    @Id protected int a;

    @OneToOne
    @JoinColumn(name = "a", insertable = false)
    First first;
}

The problem is when running:

public class Persister {

    public static void main(String[] args) {

        EntityManagerFactory aEntityManagerFactory;
        EntityManager aEntityManager;       
        aEntityManagerFactory =
                       Persistence.createEntityManagerFactory("bibit_notification_jpa");
        aEntityManager = aEntityManagerFactory.createEntityManager();

        Second aSecond = new Second();
        aSecond.a = 1;          

        First aFirst = new First();
        aFirst.a = 1;
        aFirst.second = aSecond;

        aEntityManager.getTransaction().begin();
        aEntityManager.persist(aFirst);
        aEntityManager.getTransaction().commit();

      }}

, it throws this exception:

Exception in thread "main" javax.persistence.PersistenceException: java.lang.NullPointerException
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:252)
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:120)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:51)
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
    at Persister.main(Persister.java:14)
Caused by: java.lang.NullPointerException
    at org.hibernate.cfg.OneToOneSecondPass.doSecondPass(OneToOneSecondPass.java:135)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1130)
    at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:296)
    at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1115)
    at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1233)
    at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:154)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:869)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:183)
    at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:240)
    ... 4 more

When running what? Can you provide the code you're running? And the stack trace? — Pablo Santa Cruz, Mar 25 '09 at 15:06
Can you post the code for Persistence.createEntityManagerFactory? Also, are you sure you want the class name to be Presister? Make sure that's how you spelled it everywhere. — mandaleeka, Mar 25 '09 at 15:49
Persistence.createEntityManagerFactory is in javax.persistence.Persistence. And Presister is not called any where it just contains "main" — Moro, Mar 25 '09 at 16:02
Maybe if it was a sister, and not a presister, it would work... ;) — Don Branson, Mar 25 '09 at 16:04
But seriously, where's line 14 in Presister? That would be good to know. — Don Branson, Mar 25 '09 at 16:05
I had a similar problem. After upgrading Hibernate Annotations the problem persisted, but the error message became useful. That helped me solve my mapping problem which I was unaware of. — André Chalella, Sep 11 '09 at 18:48

score 2 · Answer 1 · answered Mar 25 '09 at 16:10

2

This post: http://forum.hibernate.org/viewtopic.php?t=970823)

Seems to indicate that there's some kind of problem with annotations 3.2.x. What version are you using? If it's 3.2.x, try 3.3 or 3.4.

answered Mar 25 '09 at 16:10

Don Branson

13,631
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score 1 · Answer 2 · answered Mar 29 '09 at 20:43

1

You may want to have a look at the second example in the JavaDoc. If I read this correctly the code should be

@Entity
public class First {
    @Id protected int a;

    @OneToOne @PrimaryKeyJoinColumn
    protected Second second;
}

@Entity
public class Second {

    @Id protected int a;

    @OneToOne @PrimaryKeyJoinColumn
    First first;
}

answered Mar 29 '09 at 20:43

David Rabinowitz

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93
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Although it's worked, but as I understand I think that JPA will assume id column in First is Foreign key for PK in Second and vice versa ... Such that u didn't use "mappedBy" attribute to identify the owner of relationship. thanx – Moro Apr 02 '09 at 17:03

Why am I getting this NullPointer exception?

2 Answers2

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