001/*
002 * Copyright (C) 2012 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005 * in compliance with the License. You may obtain a copy of the License at
006 *
007 * http://www.apache.org/licenses/LICENSE-2.0
008 *
009 * Unless required by applicable law or agreed to in writing, software distributed under the License
010 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011 * or implied. See the License for the specific language governing permissions and limitations under
012 * the License.
013 */
014
015package com.google.common.reflect;
016
017import com.google.common.annotations.Beta;
018import com.google.common.collect.ForwardingMap;
019import com.google.common.collect.ImmutableMap;
020import com.google.errorprone.annotations.CanIgnoreReturnValue;
021import java.util.Map;
022
023/**
024 * A type-to-instance map backed by an {@link ImmutableMap}. See also
025 * {@link MutableTypeToInstanceMap}.
026 *
027 * @author Ben Yu
028 * @since 13.0
029 */
030@Beta
031public final class ImmutableTypeToInstanceMap<B> extends ForwardingMap<TypeToken<? extends B>, B>
032    implements TypeToInstanceMap<B> {
033
034  /** Returns an empty type to instance map. */
035  public static <B> ImmutableTypeToInstanceMap<B> of() {
036    return new ImmutableTypeToInstanceMap<B>(ImmutableMap.<TypeToken<? extends B>, B>of());
037  }
038
039  /** Returns a new builder. */
040  public static <B> Builder<B> builder() {
041    return new Builder<B>();
042  }
043
044  /**
045   * A builder for creating immutable type-to-instance maps. Example:
046   * <pre>   {@code
047   *
048   *   static final ImmutableTypeToInstanceMap<Handler<?>> HANDLERS =
049   *       ImmutableTypeToInstanceMap.<Handler<?>>builder()
050   *           .put(new TypeToken<Handler<Foo>>() {}, new FooHandler())
051   *           .put(new TypeToken<Handler<Bar>>() {}, new SubBarHandler())
052   *           .build();}</pre>
053   *
054   * <p>After invoking {@link #build()} it is still possible to add more entries and build again.
055   * Thus each map generated by this builder will be a superset of any map generated before it.
056   *
057   * @since 13.0
058   */
059  @Beta
060  public static final class Builder<B> {
061    private final ImmutableMap.Builder<TypeToken<? extends B>, B> mapBuilder =
062        ImmutableMap.builder();
063
064    private Builder() {}
065
066    /**
067     * Associates {@code key} with {@code value} in the built map. Duplicate keys are not allowed,
068     * and will cause {@link #build} to fail.
069     */
070    @CanIgnoreReturnValue
071    public <T extends B> Builder<B> put(Class<T> key, T value) {
072      mapBuilder.put(TypeToken.of(key), value);
073      return this;
074    }
075
076    /**
077     * Associates {@code key} with {@code value} in the built map. Duplicate keys are not allowed,
078     * and will cause {@link #build} to fail.
079     */
080    @CanIgnoreReturnValue
081    public <T extends B> Builder<B> put(TypeToken<T> key, T value) {
082      mapBuilder.put(key.rejectTypeVariables(), value);
083      return this;
084    }
085
086    /**
087     * Returns a new immutable type-to-instance map containing the entries provided to this builder.
088     *
089     * @throws IllegalArgumentException if duplicate keys were added
090     */
091    public ImmutableTypeToInstanceMap<B> build() {
092      return new ImmutableTypeToInstanceMap<B>(mapBuilder.build());
093    }
094  }
095
096  private final ImmutableMap<TypeToken<? extends B>, B> delegate;
097
098  private ImmutableTypeToInstanceMap(ImmutableMap<TypeToken<? extends B>, B> delegate) {
099    this.delegate = delegate;
100  }
101
102  @Override
103  public <T extends B> T getInstance(TypeToken<T> type) {
104    return trustedGet(type.rejectTypeVariables());
105  }
106
107  /**
108   * Guaranteed to throw an exception and leave the map unmodified.
109   *
110   * @deprecated unsupported operation
111   * @throws UnsupportedOperationException always
112   */
113  @CanIgnoreReturnValue
114  @Deprecated
115  @Override
116  public <T extends B> T putInstance(TypeToken<T> type, T value) {
117    throw new UnsupportedOperationException();
118  }
119
120  @Override
121  public <T extends B> T getInstance(Class<T> type) {
122    return trustedGet(TypeToken.of(type));
123  }
124
125  /**
126   * Guaranteed to throw an exception and leave the map unmodified.
127   *
128   * @deprecated unsupported operation
129   * @throws UnsupportedOperationException always
130   */
131  @CanIgnoreReturnValue
132  @Deprecated
133  @Override
134  public <T extends B> T putInstance(Class<T> type, T value) {
135    throw new UnsupportedOperationException();
136  }
137
138  /**
139   * Guaranteed to throw an exception and leave the map unmodified.
140   *
141   * @deprecated unsupported operation
142   * @throws UnsupportedOperationException always
143   */
144  @CanIgnoreReturnValue
145  @Deprecated
146  @Override
147  public B put(TypeToken<? extends B> key, B value) {
148    throw new UnsupportedOperationException();
149  }
150
151  /**
152   * Guaranteed to throw an exception and leave the map unmodified.
153   *
154   * @deprecated unsupported operation
155   * @throws UnsupportedOperationException always
156   */
157  @Deprecated
158  @Override
159  public void putAll(Map<? extends TypeToken<? extends B>, ? extends B> map) {
160    throw new UnsupportedOperationException();
161  }
162
163  @Override
164  protected Map<TypeToken<? extends B>, B> delegate() {
165    return delegate;
166  }
167
168  @SuppressWarnings("unchecked") // value could not get in if not a T
169  private <T extends B> T trustedGet(TypeToken<T> type) {
170    return (T) delegate.get(type);
171  }
172}