Package javax.persistence

Annotation Interface MapKeyColumn

@Target({METHOD,FIELD}) @Retention(RUNTIME) public @interface MapKeyColumn
Specifies the mapping for the key column of a map whose map key is a basic type. If the name element is not specified, it defaults to the concatenation of the following: the name of the referencing relationship field or property; "_"; "KEY". 
    Example:

    @Entity
    public class Item {
       @Id int id;
       ...
       @ElementCollection
       @MapKeyColumn(name="IMAGE_NAME")
       @Column(name="IMAGE_FILENAME")
       @CollectionTable(name="IMAGE_MAPPING")
       Map<String, String> images;  // map from image name to filename
       ...
    }
Since:
Java Persistence 2.0

  • Optional Element Summary

    Optional Elements
    Modifier and Type
    Optional Element
    Description
    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.
    int
    length
    (Optional) The column length.
    String
    name
    (Optional) The name of the map key column.
    boolean
    nullable
    (Optional) Whether the database column is nullable.
    int
    precision
    (Optional) The precision for a decimal (exact numeric) column.
    int
    scale
    (Optional) The scale for a decimal (exact numeric) column.
    String
    table
    (Optional) The name of the table that contains the column.
    boolean
    unique
    (Optional) Whether the column is a unique key.
    boolean
    updatable
    (Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.

  • Element Details

    • name

      String name
      (Optional) The name of the map key column. The table in which it is found depends upon the context. If the map key is for an element collection, the map key column is in the collection table for the map value. If the map key is for a ManyToMany entity relationship or for a OneToMany entity relationship using a join table, the map key column is in a join table. If the map key is for a OneToMany entity relationship using a foreign key mapping strategy, the map key column is in the table of the entity that is the value of the map.

      Defaults to the concatenation of the following: the name of the referencing relationship field or property; "_"; "KEY".

      Default:
      ""

    • unique

      boolean unique
      (Optional) Whether the column 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 corresponds to only a single column. This constraint applies in addition to any constraint entailed by primary key mapping and to constraints specified at the table level.
      Default:
      false

    • nullable

      boolean nullable
      (Optional) Whether the database column is nullable.
      Default:
      false

    • insertable

      boolean insertable
      (Optional) Whether the column is included in SQL INSERT statements generated by the persistence provider.
      Default:
      true

    • updatable

      boolean updatable
      (Optional) Whether the column is included in SQL UPDATE statements generated by the persistence provider.
      Default:
      true

    • columnDefinition

      String columnDefinition
      (Optional) The SQL fragment that is used when generating the DDL for the column.

      Defaults to the generated SQL to create a column of the inferred type.

      Default:
      ""

    • table

      String table
      (Optional) The name of the table that contains the column.

      Defaults: If the map key is for an element collection, the name of the collection table for the map value. If the map key is for a OneToMany or ManyToMany entity relationship using a join table, the name of the join table for the map. If the map key is for a OneToMany entity relationship using a foreign key mapping strategy, the name of the primary table of the entity that is the value of the map.

      Default:
      ""

    • length

      int length
      (Optional) The column length. (Applies only if a string-valued column is used.)
      Default:
      255

    • precision

      int precision
      (Optional) The precision for a decimal (exact numeric) column. (Applies only if a decimal column is used.)

      Default: 0. (The value must be set by the developer.)

      Default:
      0

    • scale

      int scale
      (Optional) The scale for a decimal (exact numeric) column. (Applies only if a decimal column is used.)
      Default:
      0