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Consider the pattern used for {{org.hibernate.annotations.ValueGenerationType}}.
In some ways this is an extension to {{GenericGenerator}}. One option is to define this annotation with the intention that it be attached to the custom {{org.hibernate.id.IdentifierGenerator}} implementation class for discovery and some basic configuration. E.g.
{code}
@ThisNewAnnotation
public class MyCustomGenerator implements IdentifierGenerator {
...
}
{code}
Like we did with {{ValueGenerationType}}, I would love for this to express how the implementation should be configured from annotation values. Not sure exactly how this would look, but something like:
{code}
/**
* Annotation to identify IdentifierGenerator implementations
*/
public @interface GeneratorImplementation {
// this allows non-indexed (Jandex) resolutions. Do we want/need it?
// The Jndex-y option is to simply find instances of this annotation
// and look it their targets
Class[] generatorImpls();
}
/**
* Extended IdentifierGenerator contract to account for annotation consumption
*/
public interface AnnotationBasedIdentifierGenerator<A extends Annotation,T extends Serializable>
extends IdentifierGenerator {
/**
* Consume the annotation (configuration)
*/
void initialize(A ann);
@Override
T generate(SessionImplementor session, Object object);
}
{code}
// Sample usage ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
{code}
/**
* My custom generator annotation
*/
public interface @UuidGenerator {
enum Strategy( RANDOM, RFC_4122 )
String name();
Strategy strategy() default RFC_4122;
}
@GeneratorImplementation
public class UuidIdentifierGenerator
implements AnnotationBasedIdentifierGenerator<UuidGenerator,UUID> {
private String generatorName;
private UUIDGenerationStrategy uuidGenStrategy;
@Override
public void initialize(UuidGenerator ann) {
this.generatorName = ann.name();
this.uuidGenStrategy = decodeStrategy( ann.strategy() );
}
private UUIDGenerationStrategy decodeStrategy(Strategy strategy) {
switch( strategy ) {
...
}
}
@Override
UUID generate(SessionImplementor session, Object object) {
return uuidGenStrategy.generateUUID( session );
}
}
public class MyEntity {
@GeneratedValue
@UuidGenerator(strategy=RANDOM)
private UUID id;
...
}
{code}
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