geode-core/src/main/java/org/apache/geode/pdx/PdxSerializer.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more contributor license
 * agreements. See the NOTICE file distributed with this work for additional information regarding
 * copyright ownership. The ASF licenses this file to You 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.apache.geode.pdx;

/**
 * The PdxSerializer interface allows domain classes to be serialized and deserialized as PDXs
 * without modification of the domain class. It only requires that the domain class have a public
 * zero-arg constructor and that it provides read and write access to the PDX serialized fields.
 * <p>
 * GemFire allows a single PdxSerializer to be configured on a cache using
 * {@link org.apache.geode.cache.CacheFactory#setPdxSerializer(PdxSerializer) setPdxSerializer} or
 * {@link org.apache.geode.cache.client.ClientCacheFactory#setPdxSerializer(PdxSerializer) client
 * setPdxSerializer}. It can also be configured in <code>cache.xml</code> using the
 * <code>pdx-serializer</code> element. The same PdxSerializer should be configured on each member
 * of a distributed system that can serialize or deserialize PDX data.
 * <p>
 * The {@link #toData toData} method is used for serialization; {@link #fromData fromData} is used
 * for deserialization. The order in which fields are serialized and deserialized in these methods
 * for the same class must match. For the same class toData and fromData must write the same fields
 * each time they are called.
 * <p>
 * If you can modify your domain class then use {@link PdxSerializable} instead.
 *
 * <p>
 * Simple example:
 *
 * <PRE>
 * public class User {
 *   public final String name;
 *   public final int userId;
 *
 *   public User(String name, int userId) {
 *     this.name = name;
 *     this.userId = userId;
 *   }
 * }
 *
 *
 * public class MyPdxSerializer implements PdxSerializer {
 *   public boolean toData(Object o, PdxWriter out) {
 *     if (o instanceof User) {
 *       User u = (User) o;
 *       out.writeString("name", u.name);
 *       out.writeInt("userId", u.userId);
 *       return true;
 *     } else {
 *       return false;
 *     }
 *   }
 *
 *   public Object fromData(Class<?> clazz, PdxReader in) {
 *     if (User.class.isAssignableFrom(clazz)) {
 *       return new User(in.readString("name"), in.readInt("userId"));
 *     } else {
 *       return null;
 *     }
 *   }
 * }
 * </PRE>
 *
 * @since GemFire 6.6
 */
public interface PdxSerializer {
  /**
   * This method is given an object to serialize as a PDX using the given writer. If it chooses to
   * do the serialization then it must return <code>true</code>; otherwise it must return
   * <code>false</code> in which case it will be serialized using standard serialization.
   *
   * @param o the object to consider serializing as a PDX
   * @param out the {@link PdxWriter} to use to serialize the object
   * @return <code>true</code> if the method serialized the object; otherwise <code>false</code>
   */
  boolean toData(Object o, PdxWriter out);

  /**
   * This method is given an class that should be instantiated and deserialized using the given
   * reader.
   *
   * @param clazz the Class of the object that should be deserialized
   * @param in the reader to use to obtain the field data
   * @return the deserialized object. <code>null</code> indicates that this PdxSerializer does not
   *         know how to deserialize the given class.
   */
  Object fromData(Class<?> clazz, PdxReader in);
}