1/* 2 * Copyright (C) 2012 The Guava Authors 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 17package com.google.common.reflect; 18 19import com.google.common.annotations.Beta; 20import com.google.common.collect.ForwardingMap; 21import com.google.common.collect.ImmutableMap; 22 23import java.util.Map; 24 25/** 26 * A type-to-instance map backed by an {@link ImmutableMap}. See also {@link 27 * MutableTypeToInstanceMap}. 28 * 29 * @author Ben Yu 30 * @since 13.0 31 */ 32@Beta 33public final class ImmutableTypeToInstanceMap<B> extends ForwardingMap<TypeToken<? extends B>, B> 34 implements TypeToInstanceMap<B> { 35 36 /** Returns an empty type to instance map. */ 37 public static <B> ImmutableTypeToInstanceMap<B> of() { 38 return new ImmutableTypeToInstanceMap<B>(ImmutableMap.<TypeToken<? extends B>, B>of()); 39 } 40 41 /** Returns a new builder. */ 42 public static <B> Builder<B> builder() { 43 return new Builder<B>(); 44 } 45 46 /** 47 * A builder for creating immutable type-to-instance maps. Example: 48 * <pre> {@code 49 * 50 * static final ImmutableTypeToInstanceMap<Handler<?>> HANDLERS = 51 * ImmutableTypeToInstanceMap.<Handler<?>>builder() 52 * .put(new TypeToken<Handler<Foo>>() {}, new FooHandler()) 53 * .put(new TypeToken<Handler<Bar>>() {}, new SubBarHandler()) 54 * .build();}</pre> 55 * 56 * <p>After invoking {@link #build()} it is still possible to add more entries 57 * and build again. Thus each map generated by this builder will be a superset 58 * of any map generated before it. 59 * 60 * @since 13.0 61 */ 62 @Beta 63 public static final class Builder<B> { 64 private final ImmutableMap.Builder<TypeToken<? extends B>, B> mapBuilder 65 = ImmutableMap.builder(); 66 67 private Builder() {} 68 69 /** 70 * Associates {@code key} with {@code value} in the built map. Duplicate 71 * keys are not allowed, and will cause {@link #build} to fail. 72 */ 73 public <T extends B> Builder<B> put(Class<T> key, T value) { 74 mapBuilder.put(TypeToken.of(key), value); 75 return this; 76 } 77 78 /** 79 * Associates {@code key} with {@code value} in the built map. Duplicate 80 * keys are not allowed, and will cause {@link #build} to fail. 81 */ 82 public <T extends B> Builder<B> put(TypeToken<T> key, T value) { 83 mapBuilder.put(key.rejectTypeVariables(), value); 84 return this; 85 } 86 87 /** 88 * Returns a new immutable type-to-instance map containing the entries 89 * provided to this builder. 90 * 91 * @throws IllegalArgumentException if duplicate keys were added 92 */ 93 public ImmutableTypeToInstanceMap<B> build() { 94 return new ImmutableTypeToInstanceMap<B>(mapBuilder.build()); 95 } 96 } 97 98 private final ImmutableMap<TypeToken<? extends B>, B> delegate; 99 100 private ImmutableTypeToInstanceMap(ImmutableMap<TypeToken<? extends B>, B> delegate) { 101 this.delegate = delegate; 102 } 103 104 @Override public <T extends B> T getInstance(TypeToken<T> type) { 105 return trustedGet(type.rejectTypeVariables()); 106 } 107 108 /** 109 * Guaranteed to throw an exception and leave the map unmodified. 110 * 111 * @throws UnsupportedOperationException always 112 */ 113 @Override public <T extends B> T putInstance(TypeToken<T> type, T value) { 114 throw new UnsupportedOperationException(); 115 } 116 117 @Override public <T extends B> T getInstance(Class<T> type) { 118 return trustedGet(TypeToken.of(type)); 119 } 120 121 /** 122 * Guaranteed to throw an exception and leave the map unmodified. 123 * 124 * @throws UnsupportedOperationException always 125 */ 126 @Override public <T extends B> T putInstance(Class<T> type, T value) { 127 throw new UnsupportedOperationException(); 128 } 129 130 @Override protected Map<TypeToken<? extends B>, B> delegate() { 131 return delegate; 132 } 133 134 @SuppressWarnings("unchecked") // value could not get in if not a T 135 private <T extends B> T trustedGet(TypeToken<T> type) { 136 return (T) delegate.get(type); 137 } 138} 139