JPA Hibernate One-to-One relationship

JPA doesn't allow the @Id annotation on a OneToOne or ManyToOne mapping. What you are trying to do is one-to-one entity association with shared primary key. The simplest case is unidirectional one-to-one with shared key:

@Entity
public class Person {
    @Id
    private int id;

    @OneToOne
    @PrimaryKeyJoinColumn
    private OtherInfo otherInfo;

    rest of attributes ...
}

The main problem with this is that JPA provides no support for shared primary key generation in OtherInfo entity. The classic book Java Persistence with Hibernate by Bauer and King gives the following solution to the problem using Hibernate extension:

@Entity
public class OtherInfo {
    @Id @GeneratedValue(generator = "customForeignGenerator")
    @org.hibernate.annotations.GenericGenerator(
        name = "customForeignGenerator",
        strategy = "foreign",
        parameters = @Parameter(name = "property", value = "person")
    )
    private Long id;

    @OneToOne(mappedBy="otherInfo")
    @PrimaryKeyJoinColumn
    public Person person;

    rest of attributes ...
}

Also, see here.

This should be working too using JPA 2.0 @MapsId annotation instead of Hibernate's GenericGenerator:

@Entity
public class Person {

    @Id
    @GeneratedValue
    public int id;

    @OneToOne
    @PrimaryKeyJoinColumn
    public OtherInfo otherInfo;

    rest of attributes ...
}

@Entity
public class OtherInfo {

    @Id
    public int id;

    @MapsId
    @OneToOne
    @JoinColumn(name="id")
    public Person person;

    rest of attributes ...
}

More details on this in Hibernate 4.1 documentation under section 5.1.2.2.7.

You just need to add @JoinColumn(name="column_name") to Host Entity relation . column_name is the database column name in person table.

@Entity
public class Person {
    @Id
    public int id;

    @OneToOne
    @JoinColumn(name="other_info")
    public OtherInfo otherInfo;

    rest of attributes ...
}

Person has a one-to-one relationship with OtherInfo: mappedBy="var_name" var_name is variable name for otherInfo in Person class.

@Entity
public class OtherInfo {
    @Id
    @OneToOne(mappedBy="otherInfo")
    public Person person;

    rest of attributes ...
}

I think you still need the primary key property in the OtherInfo class.

@Entity
public class OtherInfo {
    @Id
    public int id;

    @OneToOne(mappedBy="otherInfo")
    public Person person;

    rest of attributes ...
}

Also, you may need to add the @PrimaryKeyJoinColumn annotation to the other side of the mapping. I know that Hibernate uses this by default. But then I haven't used JPA annotations, which seem to require you to specify how the association wokrs.

I have a better way of doing this:

@Entity
public class Person {

    @OneToOne(cascade={javax.persistence.CascadeType.ALL})
    @JoinColumn(name = "`Id_OtherInfo`")
    public OtherInfo getOtherInfo() {
      return otherInfo;
    }

}

That's all

JPA Hibernate One-to-One relationship

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