001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, 013 * software distributed under the License is distributed on an 014 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 015 * KIND, either express or implied. See the License for the 016 * specific language governing permissions and limitations 017 * under the License. 018 */ 019package org.apache.reef.tang.annotations; 020 021import java.lang.annotation.*; 022 023/** 024 * Allows interfaces to specify a default implementation. 025 * <p> 026 * Note that the default can be overridden after the fact 027 * by explicitly binding a different implementation to the 028 * interface. 029 * <p> 030 * For "normal" injections of a given library, this reduces 031 * the amount of boilerplate configuration code needed, 032 * and also shrinks the Tang configuration objects that 033 * need to be passed around. 034 */ 035@Target(ElementType.TYPE) 036@Documented 037@Retention(RetentionPolicy.RUNTIME) 038public @interface DefaultImplementation { 039 Class<?> value() default Void.class; 040 041 String name() default ""; 042}