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SnappyData store based off Pivotal GemFireXD
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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire;

import java.io.*;

/**
 * CanonicalInstantiator is much like its parent
 * Instantiator except that instead of
 * needing to implement newInstance()
 * you now must implement newInstance(DataInput).
 * The addition of the DataInput parameter allows the instance
 * creator to optionally read data from the data input stream and use it to
 * decide the instance to create. This allows a value that represents a
 * canonical instance to be written by a class's {@link DataSerializer#toData}
 * and then be read by newInstance(DataInput)
 * and map it back to a canonical instance.
 * 
 * Note that {@link DataSerializer#fromData} is always called on the instance
 * returned from newInstance(DataInput).
 *
 * @author darrel
 * @since 5.1
 */
public abstract class CanonicalInstantiator extends Instantiator {
  /**
   * Creates a new CanonicalInstantiator that instantiates a given
   * class.
   *
   * @param c
   *        The DataSerializable class to register.  This
   *        class must have a static initializer that registers this
   *        Instantiator. 
   * @param classId
   *        A unique id for class c.  The
   *        classId must not be zero.
   *        This has been an int since dsPhase1.
   *
   * @throws IllegalArgumentException
   *         If c does not implement
   *         DataSerializable, classId is
   *         less than or equal to zero.
   * @throws NullPointerException
   *         If c is null
   */
  public CanonicalInstantiator(Class c, int classId) {
    super(c, classId);
  }
  
  /**
   * This method is not supported and if called will
   * throw UnsupportedOperationException.
   * Use {@link #newInstance(DataInput)} instead.
   * 
   * @throws UnsupportedOperationException in all cases
   */
  @Override
  public final DataSerializable newInstance() {
    throw new UnsupportedOperationException();
  }
  /**
   * Creates a new "empty" instance of a DataSerializable
   * class whose state will be filled in by invoking its 
   * {@link DataSerializable#fromData fromData} method.
   * @param in the data input that can be read to decide what instance to create.
   * @return the new "empty" instance.
   * @throws IOException if a read from in fails.
   * @since 5.1
   */
  public abstract DataSerializable newInstance(DataInput in)
    throws IOException;
}