1 /** 2 * Copyright (C) 2014 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 com.google.inject.Binding; 20 import com.google.inject.Key; 21 import com.google.inject.spi.Element; 22 import com.google.inject.spi.Elements; 23 24 /** 25 * A binding for a OptionalBinder. 26 * 27 * <p>Although OptionalBinders may be injected through a variety of types 28 * {@code T}, {@code Optional<T>}, {@code Optional<Provider<T>>}, etc..), an 29 * OptionalBinderBinding exists only on the Binding associated with the 30 * {@code Optional<T>} key. Other bindings can be validated to be derived from this 31 * OptionalBinderBinding using {@link #containsElement}. 32 * 33 * @param <T> The fully qualified type of the optional binding, including Optional. 34 * For example: {@code Optional<String>}. 35 * 36 * @since 4.0 37 * @author sameb (at) google.com (Sam Berlin) 38 */ 39 public interface OptionalBinderBinding<T> { 40 41 /** Returns the {@link Key} for this binding. */ 42 Key<T> getKey(); 43 44 /** 45 * Returns the default binding (set by {@link OptionalBinder#setDefault}) if one exists or null 46 * if no default binding is set. This will throw {@link UnsupportedOperationException} if it is 47 * called on an element retrieved from {@link Elements#getElements}. 48 * <p> 49 * The Binding's type will always match the type Optional's generic type. For example, if getKey 50 * returns a key of <code>Optional<String></code>, then this will always return a 51 * <code>Binding<String></code>. 52 */ 53 Binding<?> getDefaultBinding(); 54 55 /** 56 * Returns the actual binding (set by {@link OptionalBinder#setBinding}) or null if not set. 57 * This will throw {@link UnsupportedOperationException} if it is called on an element retrieved 58 * from {@link Elements#getElements}. 59 * <p> 60 * The Binding's type will always match the type Optional's generic type. For example, if getKey 61 * returns a key of <code>Optional<String></code>, then this will always return a 62 * <code>Binding<String></code>. 63 */ 64 Binding<?> getActualBinding(); 65 66 /** 67 * Returns true if this OptionalBinder contains the given Element in order to build the optional 68 * binding or uses the given Element in order to support building and injecting its data. This 69 * will work for OptionalBinderBinding retrieved from an injector and 70 * {@link Elements#getElements}. Usually this is only necessary if you are working with elements 71 * retrieved from modules (without an Injector), otherwise {@link #getDefaultBinding} and 72 * {@link #getActualBinding} are better options. 73 */ 74 boolean containsElement(Element element); 75 } 76
