Need an example of a primary-key @OneToOne mapping in Hibernate

Question

Can somebody please give me an example of a unidirectional @OneToOne primary-key mapping in Hibernate ? I've tried numerous combinations, and so far the best thing I've gotten is this :

@Entity
@Table(name = "paper_cheque_stop_metadata")
@org.hibernate.annotations.Entity(mutable = false)
public class PaperChequeStopMetadata implements Serializable, SecurityEventAware {

private static final long serialVersionUID = 1L;

@Id
@JoinColumn(name = "paper_cheque_id")
@OneToOne(cascade = {}, fetch = FetchType.EAGER, optional = false, targetEntity = PaperCheque.class)
private PaperCheque paperCheque;
}

Whenever Hibernate tries to automatically generate the schema for the above mapping, it tries to create the primary key as a blob, instead of as a long, which is the id type of PaperCheque. Can somebody please help me ? If I can't get an exact solution, something close would do, but I'd appreciate any response.

Answer 1

I saved this discussion when I implemented a couple of @OneToOne mappings, I hope it can be of use to you too, but we don't let Hibernate create the database for us.

Note the GenericGenerator annotation.

Anyway, I have this code working:

@Entity
@Table(name = "message")
public class Message implements java.io.Serializable
{
    // ...

@OneToOne(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
@PrimaryKeyJoinColumn(name = "id", referencedColumnName = "message_id")
public MessageContent getMessageContent()
{
 return messageContent;
}

    // ...
 }

@Entity
@Table(name = "message_content")
@GenericGenerator(name = "MessageContent", strategy = "foreign", parameters = { @org.hibernate.annotations.Parameter(name = "property", value = "message") })
public class MessageContent implements java.io.Serializable
{
    // ...

@Id
@Column(name = "message_id", unique = true, nullable = false)
// See http://forum.hibernate.org/viewtopic.php?p=2381079
@GeneratedValue(generator = "MessageContent")
public Integer getMessageId()
{
 return this.messageId;
}

    // ...
 }

Answer 2

Your intention is to have a 1-1 relationship between PaperChequeStopMetaData and PaperCheque? If that's so, you can't define the PaperCheque instance as the @Id of PaperChequeStopMetaData, you have to define a separate @Id column in PaperChequeStopMetaData.

Answer 3

Hey guys,

Thank you both for your answers. I kept experimenting, and here's what I got working :

@Entity
@Table(name = "paper_cheque_stop_metadata")
@org.hibernate.annotations.Entity(mutable = false)
public class PaperChequeStopMetadata implements Serializable, SecurityEventAware {

private static final long serialVersionUID = 1L;

@SuppressWarnings("unused")
@Id
@Column(name = "paper_cheque_id")
@AccessType("property")
private long id;

@OneToOne(cascade = {}, fetch = FetchType.EAGER, optional = false, targetEntity = PaperCheque.class)
@PrimaryKeyJoinColumn(name = "paper_cheque_id")
@JoinColumn(name = "paper_cheque_id", insertable = true)
@NotNull
private PaperCheque paperCheque;

@XmlAttribute(namespace = XMLNS, name = "paper-cheque-id", required = true)
public final long getId() {
 return this.paperCheque.getId();
}

public final void setId(long id) {
 //this.id = id;
 //NOOP, this is essentially a pseudo-property
}
}

This is, by all means, a disgusting hack, but it gets me everything I wanted. The paperCheque property accessors are as normal (not shown). I've run into this kind of unidirectional OneToOne mapping problem before and settled for much worse solutions, but this time I decided I was going to figure out out, so I kept hacking away at it. Once again, thank you both for your answers, it's much appreciated.

Answer 4

You should stay away from hibernate's OneToOne mapping, it is very dangerous. see http://opensource.atlassian.com/projects/hibernate/browse/HHH-2128

you are better off using ManyToOne mappings.

Answer 5

Plz provide its db script.