com.google.inject.multibindings.MapKey Maven / Gradle / Ivy
/*
* Copyright (C) 2015 Google Inc.
*
* 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 com.google.inject.multibindings;
import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
* Allows users define customized key type annotations for map bindings by annotating an annotation
* of a {@code Map}'s key type. The custom key annotation can be applied to methods also annotated
* with {@literal @}{@link ProvidesIntoMap}.
*
* A {@link StringMapKey} and {@link ClassMapKey} are provided for convenience with maps whose
* keys are strings or classes. For maps with enums or primitive types as keys, you must provide
* your own MapKey annotation, such as this one for an enum:
*
*
* {@literal @}MapKey(unwrapValue = true)
* {@literal @}Retention(RUNTIME)
* public {@literal @}interface MyCustomEnumKey {
* MyCustomEnum value();
* }
*
*
* You can also use the whole annotation as the key, if {@code unwrapValue=false}. When unwrapValue
* is false, the annotation type will be the key type for the injected map and the annotation
* instances will be the key values. If {@code unwrapValue=true}, the value() type will be the key
* type for injected map and the value() instances will be the keys values.
*
* @since 4.0
*/
@Documented
@Target(ANNOTATION_TYPE)
@Retention(RUNTIME)
public @interface MapKey {
/**
* if {@code unwrapValue} is false, then the whole annotation will be the type and annotation
* instances will be the keys. If {@code unwrapValue} is true, the value() type of key type
* annotation will be the key type for injected map and the value instances will be the keys.
*/
boolean unwrapValue() default true;
}