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IO related classes for streaming data over RMI
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/*
Copyright (c) 2007 Health Market Science, Inc.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
USA

You can contact Health Market Science at [email protected]
or at the following address:

Health Market Science
2700 Horizon Drive
Suite 200
King of Prussia, PA 19406
*/

package com.healthmarketscience.rmiio;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.Serializable;

import com.healthmarketscience.rmiio.exporter.RemoteStreamExporter;


/**
 * Implementation of RemoteIteratorClient which uses java serialization to
 * receive objects from the RemoteIteratorServer.  Objects are deserialized
 * from the underlying remote input stream as needed and returned to the
 * ultimate consumer of the objects.
 * 
 * Note, the objects are read from the ObjectInputStream using the
 * {@link java.io.ObjectInputStream#readUnshared} method.  This is because
 * memory can build up in the ObjectInputStream over time and a large data set
 * can run the client and/or server out of memory.  In general, the objects
 * being iterated over most likely do not have shared references, so nothing
 * will be lost by this choice.  However, if shared references are desired,
 * the {@link #deserializeObject} method can be overriden by a custom subclass
 * to change this behavior.
 *
 * @author James Ahlborn
 */
public class SerialRemoteIteratorClient
  extends RemoteIteratorClient
  implements Serializable
{
  private static final long serialVersionUID = 3979308768398733924L;
  
  /** the output stream which does the java serialization work */
  private transient ObjectInputStream _objIStream;

  public SerialRemoteIteratorClient(
    RemoteIteratorServer server)
    throws IOException
  {
    this(server, null);
  }
  
  public SerialRemoteIteratorClient(
    RemoteIteratorServer server,
    RemoteStreamExporter exporter)
    throws IOException
  {
    super(server, exporter);
  }

  @Override
  protected void initialize(InputStream istream)
    throws IOException
  {
    _objIStream = new ObjectInputStream(istream);
  }

  @Override
  @SuppressWarnings("unchecked")
  protected DataType readNextObject()
    throws IOException
  {
    // read next object.  the deserializeObject method will throw the
    // necessary EOFException when no more data
    try {
      return (DataType)deserializeObject(_objIStream);
    } catch(ClassNotFoundException e) {
      throw (IOException)
        (new IOException()).initCause(e);
    }
  }

  @Override
  protected void closeIterator()
    throws IOException
  {
    if(_objIStream != null) {
      // close input stream
      _objIStream.close();
    }

    // close parent
    super.closeIterator();
  }

  /**
   * Reads the next object from the given input stream.  The default
   * implementation uses {@link java.io.ObjectInputStream#readUnshared}.
   * Subclasses may choose to change this behavior by overriding this method.
   *
   * @param istream the input stream from which to read the next object
   * @return the next object read
   */
  protected Object deserializeObject(ObjectInputStream istream)
    throws IOException, ClassNotFoundException
  {
    return istream.readUnshared();
  }
  
}