marshalledobject.java

来自「linux下建立JAVA虚拟机的源码KAFFE」· Java 代码 · 共 155 行

/* MarshalledObject.java --
   Copyright (c) 1996, 1997, 1998, 1999, 2004, 2006 
   Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
 
GNU Classpath 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
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package java.rmi;

import gnu.java.rmi.RMIMarshalledObjectInputStream;
import gnu.java.rmi.RMIMarshalledObjectOutputStream;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.Serializable;

/**
 * A <code>MarshalledObject</code> consists of a serialized object which is
 * marshalled according to the RMI specification.
 * <p>
 * An object passed to the constructor is serialized and tagged with the needed
 * URL to retrieve its class definition for remote usage. If the object is a 
 * remote reference its stub is serialized instead. The instance of this 
 * marshalled object can be later retrieved by its <code>get()</code> method.
 * </p>
 *
 * @author unknown
 */
public final class MarshalledObject
  implements Serializable
{
  // The following fields are from Java API Documentation "Serialized form"
  private static final long serialVersionUID = 8988374069173025854L;

  byte[] objBytes;
  byte[] locBytes;
  int hash;

  /**
   * Constructs a <code>MarshalledObject</code> from the given object.
   * 
   * @param obj the object to marshal
   * @throws IOException if an I/O error during serialization occurs.
   */
  public MarshalledObject(Object obj) throws IOException
  {
    ByteArrayOutputStream objStream = new ByteArrayOutputStream();
    RMIMarshalledObjectOutputStream stream = 
      new RMIMarshalledObjectOutputStream(objStream);
    stream.writeObject(obj);
    stream.flush();
    objBytes = objStream.toByteArray();
    locBytes = stream.getLocBytes();

    // The following algorithm of calculating hashCode is similar to String
    hash = 0;
    for (int i = 0; i < objBytes.length; i++)
      hash = hash * 31 + objBytes[i];
    
    if (locBytes != null)
      for (int i = 0; i < locBytes.length; i++)
        hash = hash * 31 + locBytes[i];
  }

  /**
   * Checks if the given object is equal to this marshalled object.
   * 
   * <p>Marshalled objects are considered equal if they contain the
   * same serialized object. Codebase annotations where the class 
   * definition can be downloaded are ignored in the equals test.</p>
   *
   * @param obj the object to compare.   
   * @return <code>true</code> if equal, <code>false</code> otherwise.
   */
  public boolean equals(Object obj)
  {
    if (! (obj instanceof MarshalledObject))
      return false;

    // hashCode even differs, don't do the time-consuming comparisons
    if (obj.hashCode() != hash)
      return false;

    MarshalledObject aobj = (MarshalledObject) obj;
    if (objBytes == null || aobj.objBytes == null)
      return objBytes == aobj.objBytes;
    if (objBytes.length != aobj.objBytes.length)
      return false;
    for (int i = 0; i < objBytes.length; i++)
      {
        if (objBytes[i] != aobj.objBytes[i])
          return false;
      }
    // Ignore comparison of locBytes(annotation)
    return true;
  }

  /**
   * Constructs and returns a copy of the internal serialized object.
   * 
   * @return The deserialized object.
   * 
   * @throws IOException if an I/O exception occurs during deserialization.
   * @throws ClassNotFoundException if the class of the deserialized object 
   * cannot be found.
   */
  public Object get() throws IOException, ClassNotFoundException
  {
    if (objBytes == null)
      return null;
    
    RMIMarshalledObjectInputStream stream = 
      new RMIMarshalledObjectInputStream(objBytes, locBytes);
    return stream.readObject();
  }

  public int hashCode()
  {
    return hash;
  }

}