jakarta.decorator.Delegate Maven / Gradle / Ivy
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* JBoss, Home of Professional Open Source
* Copyright 2010, Red Hat, Inc., and individual contributors
* by the @authors tag. See the copyright.txt in the distribution for a
* full listing of individual contributors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package jakarta.decorator;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
*
* 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 {@link java.lang.IllegalStateException}.
*
*
*
* @Decorator
* class TimestampLogger implements Logger {
* @Inject @Delegate @Any Logger logger;
*
* void log(String message) {
* logger.log( timestamp() + ": " + message );
* }
* ...
* }
*
*
* @see Decorator @Decorator specifies that a class is a decorator.
*
* @author Gavin King
* @author Pete Muir
*/
@Target({ FIELD, PARAMETER })
@Retention(RUNTIME)
@Documented
public @interface Delegate {
}