SerializableTester.java

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * 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.common.testing;

import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import junit.framework.Assert;
import junit.framework.AssertionFailedError;

/**
 * Tests serialization and deserialization of an object, optionally asserting that the resulting
 * object is equal to the original.
 *
 * <p><b>GWT warning:</b> Under GWT, both methods simply returns their input, as proper GWT
 * serialization tests require more setup. This no-op behavior allows test authors to intersperse
 * {@code SerializableTester} calls with other, GWT-compatible tests.
 *
 * @author Mike Bostock
 * @since 10.0
 */
@GwtCompatible // but no-op!
@ElementTypesAreNonnullByDefault
public final class SerializableTester {
  private SerializableTester() {}

  /**
   * Serializes and deserializes the specified object.
   *
   * <p><b>GWT warning:</b> Under GWT, this method simply returns its input, as proper GWT
   * serialization tests require more setup. This no-op behavior allows test authors to intersperse
   * {@code SerializableTester} calls with other, GWT-compatible tests.
   *
   * <p>Note that the specified object may not be known by the compiler to be a {@link
   * java.io.Serializable} instance, and is thus declared an {@code Object}. For example, it might
   * be declared as a {@code List}.
   *
   * @return the re-serialized object
   * @throws RuntimeException if the specified object was not successfully serialized or
   *     deserialized
   */
  @CanIgnoreReturnValue
  public static <T> T reserialize(T object) {
    return Platform.reserialize(object);
  }

  /**
   * Serializes and deserializes the specified object and verifies that the re-serialized object is
   * equal to the provided object, that the hashcodes are identical, and that the class of the
   * re-serialized object is identical to that of the original.
   *
   * <p><b>GWT warning:</b> Under GWT, this method simply returns its input, as proper GWT
   * serialization tests require more setup. This no-op behavior allows test authors to intersperse
   * {@code SerializableTester} calls with other, GWT-compatible tests.
   *
   * <p>Note that the specified object may not be known by the compiler to be a {@link
   * java.io.Serializable} instance, and is thus declared an {@code Object}. For example, it might
   * be declared as a {@code List}.
   *
   * <p>Note also that serialization is not in general required to return an object that is
   * {@linkplain Object#equals equal} to the original, nor is it required to return even an object
   * of the same class. For example, if sublists of {@code MyList} instances were serializable,
   * those sublists might implement a private {@code MySubList} type but serialize as a plain {@code
   * MyList} to save space. So long as {@code MyList} has all the public supertypes of {@code
   * MySubList}, this is safe. For these cases, for which {@code reserializeAndAssert} is too
   * strict, use {@link #reserialize}.
   *
   * @return the re-serialized object
   * @throws RuntimeException if the specified object was not successfully serialized or
   *     deserialized
   * @throws AssertionFailedError if the re-serialized object is not equal to the original object,
   *     or if the hashcodes are different.
   */
  @CanIgnoreReturnValue
  public static <T> T reserializeAndAssert(T object) {
    T copy = reserialize(object);
    new EqualsTester().addEqualityGroup(object, copy).testEquals();
    Assert.assertEquals(object.getClass(), copy.getClass());
    return copy;
  }
}