| /** |
| * Copyright (C) 2006 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; |
| |
| import com.google.inject.internal.MoreTypes; |
| import static com.google.inject.internal.MoreTypes.canonicalize; |
| import com.google.inject.util.Types; |
| import static com.google.common.base.Preconditions.checkNotNull; |
| |
| import java.io.Serializable; |
| import java.lang.reflect.ParameterizedType; |
| import java.lang.reflect.Type; |
| |
| /** |
| * Represents a generic type {@code T}. Java doesn't yet provide a way to |
| * represent generic types, so this class does. Forces clients to create a |
| * subclass of this class which enables retrieval the type information even at |
| * runtime. |
| * |
| * <p>For example, to create a type literal for {@code List<String>}, you can |
| * create an empty anonymous inner class: |
| * |
| * <p> |
| * {@code TypeLiteral<List<String>> list = new TypeLiteral<List<String>>() {};} |
| * |
| * <p>Assumes that type {@code T} implements {@link Object#equals} and |
| * {@link Object#hashCode()} as value (as opposed to identity) comparison. |
| * |
| * @author crazybob@google.com (Bob Lee) |
| */ |
| public class TypeLiteral<T> implements Serializable { |
| |
| final Class<? super T> rawType; |
| final Type type; |
| final int hashCode; |
| |
| /** |
| * Constructs a new type literal. Derives represented class from type |
| * parameter. |
| * |
| * <p>Clients create an empty anonymous subclass. Doing so embeds the type |
| * parameter in the anonymous class's type hierarchy so we can reconstitute it |
| * at runtime despite erasure. |
| */ |
| @SuppressWarnings("unchecked") |
| protected TypeLiteral() { |
| this.type = getSuperclassTypeParameter(getClass()); |
| this.rawType = (Class<? super T>) MoreTypes.getRawType(type); |
| this.hashCode = MoreTypes.hashCode(type); |
| } |
| |
| /** |
| * Unsafe. Constructs a type literal manually. |
| */ |
| @SuppressWarnings("unchecked") |
| TypeLiteral(Type type) { |
| this.type = canonicalize(checkNotNull(type, "type")); |
| this.rawType = (Class<? super T>) MoreTypes.getRawType(this.type); |
| this.hashCode = MoreTypes.hashCode(this.type); |
| } |
| |
| /** |
| * Returns the type from super class's type parameter in {@link |
| * com.google.inject.internal.MoreTypes#canonicalize(Type) canonical form}. |
| */ |
| static Type getSuperclassTypeParameter(Class<?> subclass) { |
| Type superclass = subclass.getGenericSuperclass(); |
| if (superclass instanceof Class) { |
| throw new RuntimeException("Missing type parameter."); |
| } |
| ParameterizedType parameterized = (ParameterizedType) superclass; |
| return canonicalize(parameterized.getActualTypeArguments()[0]); |
| } |
| |
| /** |
| * Gets type literal from super class's type parameter. |
| */ |
| static TypeLiteral<?> fromSuperclassTypeParameter(Class<?> subclass) { |
| return new TypeLiteral<Object>(getSuperclassTypeParameter(subclass)); |
| } |
| |
| /** |
| * Gets the raw type. |
| */ |
| final Class<? super T> getRawType() { |
| return rawType; |
| } |
| |
| /** |
| * Gets underlying {@code Type} instance. |
| */ |
| public final Type getType() { |
| return type; |
| } |
| |
| /** |
| * Gets the type of this type's provider. |
| */ |
| @SuppressWarnings("unchecked") |
| final TypeLiteral<Provider<T>> providerType() { |
| // This cast is safe and wouldn't generate a warning if Type had a type |
| // parameter. |
| return (TypeLiteral<Provider<T>>) get(Types.providerOf(getType())); |
| } |
| |
| @Override public final int hashCode() { |
| return this.hashCode; |
| } |
| |
| @Override public final boolean equals(Object o) { |
| return o instanceof TypeLiteral<?> |
| && MoreTypes.equals(type, ((TypeLiteral) o).type); |
| } |
| |
| @Override public final String toString() { |
| return MoreTypes.toString(type); |
| } |
| |
| /** |
| * Gets type literal for the given {@code Type} instance. |
| */ |
| public static TypeLiteral<?> get(Type type) { |
| return new TypeLiteral<Object>(type); |
| } |
| |
| /** |
| * Gets type literal for the given {@code Class} instance. |
| */ |
| public static <T> TypeLiteral<T> get(Class<T> type) { |
| return new TypeLiteral<T>(type); |
| } |
| |
| /** |
| * Returns the canonical form of this type literal for serialization. The |
| * returned instance is always a {@code TypeLiteral}, never a subclass. This |
| * prevents problems caused by serializing anonymous types. |
| */ |
| protected final Object writeReplace() { |
| return getClass() == TypeLiteral.class |
| ? this |
| : get(type); |
| } |
| |
| private static final long serialVersionUID = 0; |
| } |