Module jakarta.persistence
Package jakarta.persistence

Annotation Interface DiscriminatorColumn

@Target(TYPE) @Retention(RUNTIME) public @interface DiscriminatorColumn
Specifies the discriminator column for the SINGLE_TABLE and JOINED inheritance mapping strategies.

The mapping strategy and discriminator column are only specified for the root of an entity class hierarchy or subhierarchy in which a different inheritance strategy is applied.

If the DiscriminatorColumn annotation is missing, and a discriminator column is required, the name of the discriminator column defaults to "DTYPE" and the discriminator type to DiscriminatorType.STRING.

Example: 

@Entity
@Table(name = "CUST")
@Inheritance(strategy = SINGLE_TABLE)
@DiscriminatorColumn(name = "DISC", discriminatorType = STRING, length = 20)
public class Customer { ... }

@Entity
public class ValuedCustomer extends Customer { ... }
Since:
1.0
See Also:

  • 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 discriminator column.
    String
    comment
    (Optional) A comment to be applied to the column.
    DiscriminatorType
    discriminatorType
    (Optional) The type of object/column to use as a class discriminator.
    int
    length
    (Optional) The column length for String-based discriminator types.
    String
    name
    (Optional) The name of column to be used for the discriminator.
    String
    options
    (Optional) A SQL fragment appended to the generated DDL which declares this column.

  • Element Details

    • name

      String name
      (Optional) The name of column to be used for the discriminator.
      Default:
      "DTYPE"

    • discriminatorType

      DiscriminatorType discriminatorType
      (Optional) The type of object/column to use as a class discriminator. Defaults to DiscriminatorType.STRING.
      Default:
      STRING

    • columnDefinition

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

      Defaults to the provider-generated SQL to create a column of the specified discriminator type.

      Default:
      ""

    • options

      String options
      (Optional) A SQL fragment appended to the generated DDL which declares this column. May not be used in conjunction with columnDefinition().
      Since:
      3.2
      Default:
      ""

    • length

      int length
      (Optional) The column length for String-based discriminator types. Ignored for other discriminator types.
      Default:
      31

    • comment

      String comment
      (Optional) A comment to be applied to the column. This is only used if table generation is in effect.
      Since:
      4.0
      Default:
      ""