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 primary key of the entity is of the same Java type as
the primary key of the entity referenced by the relationship,
the value attribute is not specified.
In this example, the parent entity has simple primary key:
@Entity
public class Employee {
@Id
long empId;
String name;
...
}
And then the dependent entity uses EmbeddedId to
declare its composite primary 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;
}
If a ManyToOne or OneToOne relationship declared by a
dependent entity is annotated MapsId, an instance of the entity
cannot be made persistent until the relationship has been assigned a
reference to an instance of the parent entity, since the identity of
the dependent entity declaring the relationship is derived from the
referenced parent entity.
- Since:
- 2.0
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Optional Element Summary
Optional Elements
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Element Details
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value
String value(Optional) The name of the attribute within the composite key to which the relationship attribute corresponds. If not explicitly specified, the relationship maps the primary key of the entity.- Default:
""
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