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@Target(value={FIELD,PARAMETER}) @Retention(value=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 ); } ... }
@Decorator specifies that a class is a decorator.
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