javax.persistence
Annotation Type MapKeyJoinColumn


@Target(value={METHOD,FIELD})
@Retention(value=RUNTIME)
public @interface MapKeyJoinColumn

Specifies a mapping to an entity that is a map key. The map key join column is in the collection table, join table, or table of the target entity that is used to represent the map. If no MapKeyJoinColumn annotation is specified, a single join column is assumed and the default values apply.


    Example 1:

    @Entity
    public class Company {
       @Id int id;
       ...
       @OneToMany   // unidirectional
       @JoinTable(name="COMPANY_ORGANIZATION",
                  joinColumns=@JoinColumn(name="COMPANY"),
                  inverseJoinColumns=@JoinColumn(name="VICEPRESIDENT"))
       @MapKeyJoinColumn(name="DIVISION")
       Map<Division, VicePresident> organization;
    }

    Example 2:

    @Entity
    public class VideoStore {
       @Id int id;
       String name;
       Address location;
       ...
       @ElementCollection
       @CollectionTable(name="INVENTORY",
                        joinColumns=@JoinColumn(name="STORE"))
       @Column(name="COPIES_IN_STOCK")
       @MapKeyJoinColumn(name="MOVIE", referencedColumnName="ID")
       Map<Movie, Integer> videoInventory;
       ...
     }

     @Entity
     public class Movie {
        @Id long id;
        String title;
        ...
     }

     Example 3:

     @Entity
     public class Student {
        @Id int studentId;
        ...
        @ManyToMany  // students and courses are also many-many
        @JoinTable(name="ENROLLMENTS",
                   joinColumns=@JoinColumn(name="STUDENT"),
                   inverseJoinColumns=@JoinColumn(name="SEMESTER"))
        @MapKeyJoinColumn(name="COURSE")
        Map<Course, Semester>  enrollment;
        ...
     }
 

Since:
Java Persistence 2.0

Optional Element Summary
 java.lang.String columnDefinition
          (Optional) The SQL fragment that is used when generating the DDL for the column.
 boolean insertable
          (Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.
 java.lang.String name
          (Optional) The name of the foreign key column for the map key.
 boolean nullable
          (Optional) Whether the foreign key column is nullable.
 java.lang.String referencedColumnName
          (Optional) The name of the column referenced by this foreign key column.
 java.lang.String table
          (Optional) The name of the table that contains the foreign key column.
 boolean unique
          (Optional) Whether the property is a unique key.
 boolean updatable
          (Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.
 

name

public abstract java.lang.String name
(Optional) The name of the foreign key column for the map key. The table in which it is found depends upon the context.

Default (only applies if a single join column is used.) The concatenation of the following: the name of the referencing relationship property or field of the referencing entity or embeddable class; "_"; "KEY".

Default:
""

referencedColumnName

public abstract java.lang.String referencedColumnName
(Optional) The name of the column referenced by this foreign key column. The referenced column is in the table of the target entity.

Default (only applies if single join column is being used.) The same name as the primary key column of the referenced table

Default:
""

unique

public abstract boolean unique
(Optional) Whether the property is a unique key. This is a shortcut for the UniqueConstraint annotation at the table level and is useful for when the unique key constraint is only a single field.

Default:
false

nullable

public abstract boolean nullable
(Optional) Whether the foreign key column is nullable.

Default:
false

insertable

public abstract boolean insertable
(Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.

Default:
true

updatable

public abstract boolean updatable
(Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.

Default:
true

columnDefinition

public abstract java.lang.String columnDefinition
(Optional) The SQL fragment that is used when generating the DDL for the column. Defaults to SQL generated by the provider for the column.

Default:
""

table

public abstract java.lang.String table
(Optional) The name of the table that contains the foreign key column.

Default:

Default:
""


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Generated on 10-February-2011 12:41


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