jakarta.persistence.EmbeddedId

Specifies that the annotated persistent field or property of an entity class or mapped superclass is the composite primary key of the entity. The type of the annotated field or property must be an embeddable type, and must be explicitly annotated Embeddable.

If a field or property of an entity class is annotated EmbeddedId, then no other field or property of the entity may be annotated Id or EmbeddedId, and the entity class must not declare an IdClass.

The embedded primary key type must implement Annotation.java.lang.annotation.Annotation/equals(Object) and Annotation.java.lang.annotation.Annotation/hashCode(), defining value equality consistently with equality of the mapped primary key of the database table.

The AttributeOverride annotation may be used to override the column mappings declared within the embeddable class.

The MapsId annotation may be used in conjunction with the EmbeddedId annotation to declare a derived primary key.

If the entity has a derived primary key, the AttributeOverride annotation may only be used to override those attributes of the embedded id that do not correspond to the relationship to the parent entity.

Relationship mappings defined within an embedded primary key type are not supported.

Example 1:

 @Entity
 public class Employee {
     @EmbeddedId
     protected EmployeePK empPK;
 ...
 }

 public record EmployeePK(String empName, Date birthDay) {}

Example 2:

 @Embeddable
 public class DependentId {
     String name;
     EmployeeId empPK;   // corresponds to primary key type of Employee
 }

 @Entity
 public class Dependent {
     // default column name for "name" attribute is overridden
     @AttributeOverride(name = "name", column = @Column(name = "dep_name"))
     @EmbeddedId
     DependentId id;
     ...
     @MapsId("empPK")
     @ManyToOne
     Employee emp;
 }

See Also:

Embeddable

MapsId

IdClass

Since:

Jakarta Persistence (JPA) 1.0