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.
We have a lot of examples around us that demonstrate this one-to-one mapping. One person has one passport, a passport is associated with a single person.
Identifiers in Hibernate represent the primary key of an entity. This implies the values are unique so that they can identify a specific entity, that they aren't null and that they won't be modified. Hibernate provides a few different ways to define identifiers.
One To Many Mapping in Hibernate. In simple terms, one to many mapping means that one row in a table can be mapped to multiple rows in another table. For example, think of a Cart system where we have another table for Items. A cart can have multiple items, so here we have one to many mapping.
@OneToOne. @OneToOne annotation marks the relationship between two entities with one-to-one multiplicity. It is not normally necessary to specify the associated target entity explicitly since it can usually be inferred from the type of the object being referenced.
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;
}
}
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.
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