1 /* 2 * Copyright (C) 2015 Google Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.inject.multibindings; 18 19 import static java.lang.annotation.ElementType.ANNOTATION_TYPE; 20 import static java.lang.annotation.RetentionPolicy.RUNTIME; 21 22 import java.lang.annotation.Documented; 23 import java.lang.annotation.Retention; 24 import java.lang.annotation.Target; 25 26 /** 27 * Allows users define customized key type annotations for map bindings by annotating an annotation 28 * of a {@code Map}'s key type. The custom key annotation can be applied to methods also annotated 29 * with {@literal @}{@link ProvidesIntoMap}. 30 * 31 * <p>A {@link StringMapKey} and {@link ClassMapKey} are provided for convenience with maps whose 32 * keys are strings or classes. For maps with enums or primitive types as keys, you must provide 33 * your own MapKey annotation, such as this one for an enum: 34 * 35 * <pre> 36 * {@literal @}MapKey(unwrapValue = true) 37 * {@literal @}Retention(RUNTIME) 38 * public {@literal @}interface MyCustomEnumKey { 39 * MyCustomEnum value(); 40 * } 41 * </pre> 42 * 43 * You can also use the whole annotation as the key, if {@code unwrapValue=false}. When unwrapValue 44 * is false, the annotation type will be the key type for the injected map and the annotation 45 * instances will be the key values. If {@code unwrapValue=true}, the value() type will be the key 46 * type for injected map and the value() instances will be the keys values. 47 * 48 * @since 4.0 49 */ 50 @Documented 51 @Target(ANNOTATION_TYPE) 52 @Retention(RUNTIME) 53 public @interface MapKey { 54 /** 55 * if {@code unwrapValue} is false, then the whole annotation will be the type and annotation 56 * instances will be the keys. If {@code unwrapValue} is true, the value() type of key type 57 * annotation will be the key type for injected map and the value instances will be the keys. 58 */ unwrapValue()59 boolean unwrapValue() default true; 60 } 61