项目中用到的JPA Annotation 之一：DiscriminatorColumn

Target:

Classes

Specifies the discriminator column for the SINGLE_TABLE and JOINED Inheritance mapping strategies.

The strategy and the discriminator column are only specified in 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:

JPA 1.0

See Also:

DiscriminatorValue

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 value:

""

Since:

JPA 1.0

DiscriminatorType discriminatorType

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

Default value:

javax.persistence.DiscriminatorType.STRING

Since:

JPA 1.0

int length

(Optional) The column length for String-based discriminator types. Ignored for other discriminator types.

Default value:

31

Since:

JPA 1.0

String name

(Optional) The name of column to be used for the discriminator.

Default value:

"DTYPE"

Since:

JPA 1.0