Note: This ORM/SQL annotation is silently ignored by ObjectDB

288 words

javax.persistence.MapsId - JPA annotation

javax.persistence
Annotation MapsId

Target:
Fields (including property get methods)
Designates a ManyToOne or OneToOne relationship attribute that provides the mapping for an EmbeddedId primary key, an attribute within an EmbeddedId primary key, or a simple primary key of the parent entity. The value element specifies the attribute within a composite key to which the relationship attribute corresponds. If the entity's primary key is of the same Java type as the primary key of the entity referenced by the relationship, the value attribute is not specified.

Example:

    // parent entity has simple primary key
 
    @Entity
    public class Employee {
       @Id long empId;
       String name;
       ...
    } 
 
    // dependent entity uses EmbeddedId for composite key
 
    @Embeddable
    public class DependentId {
       String name;
       long empid;   // corresponds to primary key type of Employee
    }
 
    @Entity
    public class Dependent {
       @EmbeddedId DependentId id;
        ...
       @MapsId("empid")  //  maps the empid attribute of embedded id
       @ManyToOne Employee emp;
    }
Since:
JPA 2.0
String value
(Optional) The name of the attribute within the composite key to which the relationship attribute corresponds.
(Optional) The name of the attribute within the composite key to which the relationship attribute corresponds. If not supplied, the relationship maps the entity’s primary key.
Default value:
""
Since:
JPA 2.0

This documentation page is derived (with some adjustments) from the open source JPA 2 RI (EclipseLink)
and is available under the terms of the Eclipse Public License, v. 1.0 and Eclipse Distribution License, v. 1.0.
Object Relational Mapping (ORM) JPA 2 providers include Hibernate, EclipseLink, TopLink, OpenJPA and DataNucleus.
Object DB is not an ORM JPA implementation but an Object Database for Java with built in JPA 2 support.