Package org.hibernate.annotations

Annotation Type ValueGenerationType

@Target(ANNOTATION_TYPE)
@Retention(RUNTIME)
public @interface ValueGenerationType

Meta-annotation used to mark another annotation as providing configuration for a custom value generation strategy. This is the best way to work with customized value generation in Hibernate.

For example, if we have a custom value generator:

 public class SKUGeneration
         implements BeforeExecutionGenerator {
     public SKUGeneration(SKU sku, Member annotatedMember,
                          GeneratorCreationContext context) {
         ...
     }
     ...
 }
 

Then we may also define an annotation which associates this generator with a field or property of an entity and supplies configuration parameters:

 @ValueGenerationType(generatedBy = SKUGeneration.class)
 @Retention(RUNTIME) @Target({METHOD,FIELD})
 public @interface SKU {}
 

and we may use it as follows:

 @SKU String sku;
 

No more than one generator annotation may be placed on a given property.

Adding a generator annotation to an entity property causes the value of the property to be generated when any SQL statement to insert or update the entity is executed.

Every generator annotation type has an Generator implementation which is responsible for generating values. It must be either:

• a BeforeExecutionGenerator, for values that are generated in Java code, using a ValueGenerator, or
• an OnExecutionGenerator, for values which are generated by the database.

A generator annotation may have members, which are used to configure the value generator, if either:

• the value generator implements AnnotationBasedGenerator, or
• the value generator class has a constructor with the same signature as AnnotationBasedGenerator.initialize(A, java.lang.reflect.Member, org.hibernate.generator.GeneratorCreationContext).

There are several excellent examples of the use of this machinery right here in this package. TenantId and its corresponding generator TenantIdGeneration are a good place to start.

A @ValueGenerationType annotation must have retention policy RetentionPolicy.RUNTIME.

See Also:

Generator, BeforeExecutionGenerator, OnExecutionGenerator, AnnotationBasedGenerator

Required Element Summary

Required Elements

Modifier and Type	Required Element	Description
Class<? extends Generator>	generatedBy	A class which implements Generator.

Element Detail

generatedBy

Class<? extends Generator> generatedBy

A class which implements Generator.