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The implementation module of Ehcache 3
There is a newer version: 3.3.1
/*
 * Copyright Terracotta, 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 org.ehcache.impl.serialization;

import java.io.Closeable;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamClass;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.Map;
import org.ehcache.spi.serialization.SerializerException;
import org.ehcache.spi.serialization.Serializer;
import org.ehcache.core.spi.service.FileBasedPersistenceContext;

/**
 * A trivially compressed Java serialization based serializer with persistent mappings.
 * 
 * Class descriptors in the resultant bytes are encoded as integers.  Mappings
 * between the integer representation and the {@link ObjectStreamClass}, and the
 * {@code Class} and the integer representation are stored in a single on-heap
 * map.
 */
public class CompactPersistentJavaSerializer implements Serializer, Closeable {

  private final File stateFile;
  private final CompactJavaSerializer serializer;

  /**
   * Constructor to enable this serializer as a persistent one.
   *
   * @param classLoader the classloader to use
   * @param persistence the persistence context to use
   *
   * @see Serializer
   */
  public CompactPersistentJavaSerializer(ClassLoader classLoader, FileBasedPersistenceContext persistence) throws IOException, ClassNotFoundException {
    this.stateFile = new File(persistence.getDirectory(), "CompactPersistentJavaSerializer.state");
    if (stateFile.exists()) {
      serializer = new CompactJavaSerializer(classLoader, readSerializationMappings(stateFile));
    } else {
      serializer = new CompactJavaSerializer(classLoader);
    }
  }

  /**
   * Closes this serializer instance, causing mappings to be persisted.
   *
   * @throws IOException in case mappings cannot be persisted.
   */
  @Override
  public final void close() throws IOException {
    try {
      writeSerializationMappings(stateFile, serializer.getSerializationMappings());
    } finally {
      serializer.close();
    }
  }

  private static Map readSerializationMappings(File stateFile) throws IOException, ClassNotFoundException {
    FileInputStream fin = new FileInputStream(stateFile);
    try {
      ObjectInputStream oin = new ObjectInputStream(fin);
      try {
        return (Map) oin.readObject();
      } finally {
        oin.close();
      }
    } finally {
      fin.close();
    }
  }

  private static void writeSerializationMappings(File stateFile, Map mappings) throws IOException {
    OutputStream fout = new FileOutputStream(stateFile);
    try {
      ObjectOutputStream oout = new ObjectOutputStream(fout);
      try {
        oout.writeObject(mappings);
      } finally {
        oout.close();
      }
    } finally {
      fout.close();
    }
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public ByteBuffer serialize(T object) throws SerializerException {
    return serializer.serialize(object);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public T read(ByteBuffer binary) throws ClassNotFoundException, SerializerException {
    return serializer.read(binary);
  }

  /**
   * {@inheritDoc}
   */
  @Override
  public boolean equals(T object, ByteBuffer binary) throws ClassNotFoundException, SerializerException {
    return serializer.equals(object, binary);
  }

}