Problems with OneToOne mapping

[hal arres]

Hi all,

I want to do a one-to-one mapping with hibernate. In the beginning it seems to be very easy, but now I am not so sure. I tried and tried, but I always failed.

Maybe someone of you could help me to fix my problem. I become more and more desprate...

To do this mapping I changed two existing tables to the following structure:

    
DOCUMENT
    ID (PK)

EVENTPROFILE
    ID (PK & FK)

Now I want to map them into my Entities, which look like this:

    
@Entity
@Table(name = "DOCUMENT")
public class Document 
        implements Serializable {

    @Id
    @SequenceGenerator(name = "seq", sequenceName = "sq_key")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator="seq")
    @Column(name = "ID")
    private Long id;

    @OneToOne(cascade=CascadeType.ALL)
    @PrimaryKeyJoinColumn(name="ID", referencedColumnName="TEP_ID") 
    private Eventprofile eventprofile;


    public Long getId() {
        return id;
    }

    public Eventprofile getEventprofile() {
        if (eventprofile == null) {
            eventprofile = new Eventprofile();
        }
        return eventprofile;
    }
...

and

    
@Entity
@Table(name = "EVENTPROFILE")
public class Eventprofile {

    @Id
    @Column(name = "TEP_ID")
    @GenericGenerator(name = "foreign_pk", strategy = "foreign",
            parameters = @Parameter(name = "property", value = "document"))
    @GeneratedValue(generator = "foreign_pk")
    private Long id;

    @OneToOne(mappedBy="eventprofile", fetch = FetchType.LAZY)
    private Document document;

    public Document getDocument() {
        return document;
    }
...

When I trying to read this entities everything works fine, but as soon as I want to insert one I get the following exception:

    
...
Caused by: org.hibernate.id.IdentifierGenerationException: attempted to assign id from null one-to-one property: document
	at org.hibernate.id.ForeignGenerator.generate(ForeignGenerator.java:68)
	at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:122)
	at org.hibernate.ejb.event.EJB3MergeEventListener.saveWithGeneratedId(EJB3MergeEventListener.java:43)
	at org.hibernate.event.def.DefaultMergeEventListener.mergeTransientEntity(DefaultMergeEventListener.java:314)
	at org.hibernate.event.def.DefaultMergeEventListener.entityIsTransient(DefaultMergeEventListener.java:282)
	at org.hibernate.event.def.DefaultMergeEventListener.onMerge(DefaultMergeEventListener.java:237)
	at org.hibernate.impl.SessionImpl.fireMerge(SessionImpl.java:715)
...

This is the part where I am trying to insert the entity:

  
    @PersistenceContext(unitName="default")
    private EntityManager em;

    @Test
    public void testDocumentSaveing() {
        Document document = new Document();
        document.setRemarks("My Hibernate-Unittest");
        Eventprofile eventprofile = document.getEventprofile();
        eventprofile.setEventtypeText("My Eventtypetext.");

        em.merge(document);
    }  

In the row of sql statements I can see, that the sequence is executed, but this is all.

I searched very long for a solution and tried different suggestions, but none worked.
So I want to ask you, if someone could help.
It would be very nice...

All the best,
arres

[Oliver Tik]

Hi Hal,

i'm not sure, if I really understood your problem. Do you want to use the Document's ID/PK as the EventProfile's ID/PK?

Why then do you try to generate this ID instead of setting it programmatically? You could just drop all this generation annotations in Eventprofile

# public class Eventprofile {
#
# @Id
# @Column(name = "TEP_ID")
# private Long id;

and then

# Document document = new Document();
# document.setRemarks("My Hibernate-Unittest");
# em.persist(document);
# Eventprofile eventprofile = document.getEventprofile();
# eventprofile.setEventtypeText("My Eventtypetext.");
# eventprofile.setID(document.getID())
# document = em.merge(document);

Why wouldn't this work?

Cheers
Oliver

[hal arres]

Hi Oliver,

thank you for your answer.

Your right, I use the documents pk as the eventprofile PK.
The way to set it programatically does work, but if I do it this way, I have to save each entity on its own. But I want to safe both objects at once.
Or is it the standard-way to safe each object in a One-To-One relation on its own?

I found a way to do safe the relation at once by using the method "persist" instead of "merge".
But now I am a little bit confused, because Many-To-One or One-To-Many relations can be persist by using "merge".
Do you know why merge does not work for One-To-One?

Greetings,
Hal