@Target({FIELD,PARAMETER}) @Retention(RUNTIME) @Documented public @interface Delegate

Identifies the delegate injection point of a decorator. May be applied to a field, bean constructor parameter or initializer method parameter of a decorator bean class.

 @Decorator
 class TimestampLogger implements Logger {
    @Inject @Delegate @Any Logger logger;
    ...
 }

 @Decorator
 class TimestampLogger implements Logger {
    private Logger logger;

    @Inject
    public TimestampLogger(@Delegate @Debug Logger logger) {
       this.logger=logger;
    }
    ...
 }

A decorator must have exactly one delegate injection point. The delegate injection point must be an injected field, initializer method parameter or bean constructor method parameter.

The container injects a delegate object to the delegate injection point. The delegate object implements the delegate type and delegates method invocations along the decorator stack. When the container calls a decorator during business method interception, the decorator may invoke any method of the delegate object. If a decorator invokes the delegate object at any other time, the invoked method throws an IllegalStateException.

 @Decorator
 class TimestampLogger implements Logger {
    @Inject @Delegate @Any Logger logger;

    void log(String message) {
       logger.log( timestamp() + ": " + message );
    }
    ...
 }

CDI Lite implementations are not required to provide support for decorators.

Author:

Gavin King, Pete Muir

See Also:

Annotation Interface Delegate