src/com/google/inject/internal/Types.java

/**
 * Copyright (C) 2008 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.internal;

import java.io.Serializable;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Arrays;

/**
 * @author crazybob@google.com (Bob Lee)
 */
public class Types {
  private Types() {}

  /**
   * Returns an equal Type that implements {@code Serializable}. Unfortunately,
   * the Sun JDK 1.5 Type classes (among others) are not serializable, so we
   * replace them with our own serializable implementations here.
   */
  public static Type makeSerializable(Type type) {
    if (type instanceof ParameterizedTypeImpl
        || type instanceof GenericArrayTypeImpl) {
      return type;

    } else if (type instanceof ParameterizedType) {
      ParameterizedType p = (ParameterizedType) type;
      return newParameterizedType(p.getOwnerType(),
          p.getRawType(), p.getActualTypeArguments());

    } else if (type instanceof GenericArrayType) {
      GenericArrayType g = (GenericArrayType) type;
      return newGenericArrayType(g.getGenericComponentType());

    } else {
      // type is either serializable as-is or unsupported
      return type;
    }
  }

  public static ParameterizedType newTypeWithArgument(Type rawType, Type... typeArguments) {
    return newParameterizedType(null, rawType, typeArguments);
  }

  public static ParameterizedType newParameterizedType(
      Type ownerType, Type rawType, Type... typeArguments) {
    return new ParameterizedTypeImpl(ownerType, rawType, typeArguments);
  }

  public static GenericArrayType newGenericArrayType(Type componentType) {
    return new GenericArrayTypeImpl(componentType);
  }

  public static Class<?> getRawType(Type type) {
    if (type instanceof Class<?>) {
      // type is a normal class.
      return (Class<?>) type;

    } else if (type instanceof ParameterizedType) {
      ParameterizedType parameterizedType = (ParameterizedType) type;

      // I'm not exactly sure why getRawType() returns Type instead of Class.
      // Neal isn't either but suspects some pathological case related
      // to nested classes exists.
      Type rawType = parameterizedType.getRawType();
      if (!(rawType instanceof Class<?>)) {
        throw unexpectedType(rawType, Class.class);
      }
      return (Class<?>) rawType;

    } else if (type instanceof GenericArrayType) {
      // TODO: Is this sufficient?
      return Object[].class;

    } else {
      // type is a parameterized type.
      throw unexpectedType(type, ParameterizedType.class);
    }
  }

  private static AssertionError unexpectedType(Type type, Class<?> expected) {
    return new AssertionError(
        "Unexpected type. Expected: " + expected.getName()
        + ", got: " + type.getClass().getName()
        + ", for type literal: " + type.toString() + ".");
  }

  /**
   * Returns true if {@code a} and {@code b} are equal.
   */
  public static boolean equals(Type a, Type b) {
    if (a == b) {
      // also handles (a == null && b == null)
      return true;

    } else if (a instanceof Class) {
      // Class already specifies equals().
      return a.equals(b);

    } else if (a instanceof ParameterizedType) {
      if (!(b instanceof ParameterizedType)) {
        return false;
      }

      ParameterizedType pa = (ParameterizedType) a;
      ParameterizedType pb = (ParameterizedType) b;
      return Objects.equal(pa.getOwnerType(), pb.getOwnerType())
          && pa.getRawType().equals(pb.getRawType())
          && Arrays.equals(pa.getActualTypeArguments(), pb.getActualTypeArguments());

    } else if (a instanceof GenericArrayType) {
      if (!(b instanceof GenericArrayType)) {
        return false;
      }

      GenericArrayType ga = (GenericArrayType) a;
      GenericArrayType gb = (GenericArrayType) b;
      return equals(ga.getGenericComponentType(), gb.getGenericComponentType());

    } else {
      // This isn't a type we support. Could be a generic array type, wildcard
      // type, etc.
      return false;
    }
  }

  /**
   * Returns the hashCode of {@code type}.
   */
  public static int hashCode(Type type) {
    if (type instanceof Class) {
      // Class specifies hashCode().
      return type.hashCode();

    } else if (type instanceof ParameterizedType) {
      ParameterizedType p = (ParameterizedType) type;
      return Arrays.hashCode(p.getActualTypeArguments())
          ^ p.getRawType().hashCode()
          ^ Objects.hashCode(p.getOwnerType());

    } else if (type instanceof GenericArrayType) {
      return hashCode(((GenericArrayType) type).getGenericComponentType());

    } else {
      // This isn't a type we support. Could be a generic array type, wildcard
      // type, etc.
      return Objects.hashCode(type);
    }
  }

  public static String toString(Type type) {
    if (type instanceof Class<?>) {
      return ((Class) type).getName();

    } else if (type instanceof ParameterizedType) {
      ParameterizedType parameterizedType = (ParameterizedType) type;
      Type[] arguments = parameterizedType.getActualTypeArguments();
      Type ownerType = parameterizedType.getOwnerType();
      StringBuilder stringBuilder = new StringBuilder();
      if (ownerType != null) {
        stringBuilder.append(toString(ownerType)).append(".");
      }
      stringBuilder.append(toString(parameterizedType.getRawType()))
          .append("<")
          .append(toString(arguments[0]));
      for (int i = 1; i < arguments.length; i++) {
        stringBuilder.append(", ").append(toString(arguments[i]));
      }
      return stringBuilder.append(">").toString();

    } else if (type instanceof GenericArrayType) {
      return toString(((GenericArrayType) type).getGenericComponentType()) + "[]";

    } else {
      return type.toString();
    }
  }

  private static class ParameterizedTypeImpl implements ParameterizedType, Serializable {
    private final Type ownerType;
    private final Type rawType;
    private final Type[] typeArguments;

    private ParameterizedTypeImpl(Type ownerType, Type rawType, Type... typeArguments) {
      this.ownerType = ownerType == null ? null : makeSerializable(ownerType);
      this.rawType = makeSerializable(rawType);
      this.typeArguments = typeArguments.clone();
      for (int t = 0; t < this.typeArguments.length; t++) {
        this.typeArguments[t] = makeSerializable(this.typeArguments[t]);
      }
    }

    public Type[] getActualTypeArguments() {
      return typeArguments.clone();
    }

    public Type getRawType() {
      return rawType;
    }

    public Type getOwnerType() {
      return ownerType;
    }

    @Override public boolean equals(Object other) {
      return other instanceof ParameterizedType
          && Types.equals(this, (ParameterizedType) other);
    }

    @Override public int hashCode() {
      return Types.hashCode(this);
    }

    @Override public String toString() {
      return Types.toString(this);
    }

    private static final long serialVersionUID = 0;
  }

  private static class GenericArrayTypeImpl implements GenericArrayType, Serializable {
    private final Type componentType;

    private GenericArrayTypeImpl(Type componentType) {
      this.componentType = componentType;
    }

    public Type getGenericComponentType() {
      return componentType;
    }

    @Override public boolean equals(Object o) {
      return o instanceof GenericArrayType
          && Types.equals(this, (GenericArrayType) o);
    }

    @Override public int hashCode() {
      return Types.hashCode(this);
    }

    @Override public String toString() {
      return Types.toString(this);
    }

    private static final long serialVersionUID = 0;
  }
}