message.java

JXTA源文件

/*
 *
 * $Id: Message.java,v 1.46 2005/11/04 04:59:28 bondolo Exp $
 *
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA"
 *    must not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS  OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 */

package net.jxta.endpoint;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.PrintWriter;
import java.io.Serializable;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.Vector;

import java.io.IOException;
import java.util.ConcurrentModificationException;
import java.util.NoSuchElementException;

import org.apache.log4j.Level;
import org.apache.log4j.Logger;

import net.jxta.document.MimeMediaType;
import net.jxta.util.AbstractSimpleSelectable;
import net.jxta.util.SimpleSelectable;

import net.jxta.impl.id.UUID.UUID;
import net.jxta.impl.id.UUID.UUIDFactory;

/**
 * Messages are abstract containers for protocol messages within JXTA. Services 
 * and applications are expected to use Messages as the basis for any protocols
 * implemented within JXTA. Messages are exchanged through the
 * {@link net.jxta.endpoint.EndpointService} or
 * {@link net.jxta.pipe.PipeService}.
 *
 * <p/>A Message is composed of an ordered list of zero or more
 * {@link net.jxta.endpoint.MessageElement MessageElements}. Each
 * {@link net.jxta.endpoint.MessageElement} is associated with a namespace at
 * the time it is added to the message. Duplicate
 * {@link net.jxta.endpoint.MessageElement MessageElements} are permitted.
 *
 * <p/><b>Messages are not synchronized. All of the iterators returned by this implementation are
 * "fail-fast". Concurrent modification from multiple threads will produce unexpected results.</b>
 *
 * @see  net.jxta.endpoint.MessageElement
 * @see  net.jxta.endpoint.EndpointAddress
 * @see  net.jxta.endpoint.EndpointService
 * @see  net.jxta.pipe.InputPipe
 * @see  net.jxta.pipe.OutputPipe
 * @see  net.jxta.pipe.PipeService
 **/
public class Message extends AbstractSimpleSelectable implements Serializable {
    
    /**
     *  Log4J Logger
     **/
    private static final transient Logger LOG = Logger.getLogger( Message.class.getName() );
    
    /**
     *  Magic value for this format of serialization version.
     **/
    private static final long serialVersionUID = 3418026921074097757L;
    
    /**
     *  If <tt>true</tt>, then modification logging be activated. This is a very 
     *  expensive option as it causes a stack crawl to be captured for every 
     *  message modification.
     *
     *  <p/>To enable modification tracking, set to <tt>true</tt> and recompile.
     **/
    protected static final boolean LOG_MODIFICATIONS = false;
    
    /**
     *  If <tt>true</tt>, then a special tracking element is added to the 
     *  message. This provides the ability to follow messages throughout the 
     *  network. If a message has a tracking element then it will be used in 
     *  the <tt>toString()</tt>  representation.
     *
     *  <p/>The element is currently named "Tracking UUID" and is stored in the
     *  "jxta" namespace. The element contains an IETF version 1 UUID in string
     *  form.
     *
     *  <p/>To enable addition of a tracking element, set to <tt>true</tt>
     *  and recompile.
     **/
    protected static final boolean GLOBAL_TRACKING_ELEMENT = false;
    
    /**
     *  Incremented for each standalone message instance. {@see #lineage} for
     *  information about how message numbers can be used.
     **/
    private static transient volatile int messagenumber = 1;
    
    /**
     *  This string identifies the namespace which is assumed when calls are
     *  made that don't include a namespace specification.
     **/
    protected final String defaultNamespace;
    
    /**
     *  the namespaces in this message and the elements in each.
     *
     *  <ul>
     *      <li>keys are {@link java.lang.String}</li>
     *      <li>values are {@link java.util.List}
     *          <ul>
     *              <li>values are {@link net.jxta.endpoint.MessageElement}</li>
     *          </ul>
     *      </li>
     *  </ul>
     **/
    protected transient Map namespaces = new HashMap();
    
    /**
     *  List of the elements.
     *
     *  <ul>
     *      <li>values are {@link net.jxta.endpoint.Message.element}</li>
     *  </ul>
     **/
    protected transient List elements = new ArrayList();
    
    /**
     *  Message properties HashMap
     *
     *  <ul>
     *      <li>keys are {@link java.lang.Object}</li>
     *      <li>values are {@link java.lang.Object}</li>
     *  </ul>
     **/
    protected transient Map properties = Collections.synchronizedMap(new HashMap());

    /**
     *  A list of {@link java.lang.Integer} which details the lineage (history
     *  of cloning) that produced this message. This message's number is index
     *  0, all of the ancestors are in order at higher indexes.
     *
     *  <p/>Message numbers are not part of the message content and are only 
     *  stored locally. The are useful for following messages throughout their
     *  lifetime and is normally shown as part of the <tt>toString()</tt>
     *  display for Messages.
     **/
    protected transient List lineage = new ArrayList();
    
    /**
     *  Modification count of this message. Can be used to detect message being
     *  concurrently modified when message is shared.
     *
     *  <p/>The modification count is part of the <tt>toString()</tt>
     *  display for Messages.
     **/
    protected transient volatile int modCount = 0;
    
    /**
     *  cached aggregate size of all the memeber elements. Used by
     *  {@link #getByteLength()}
     **/
    protected transient long cachedByteLength = 0;
    
    /**
     *  modcount at the time the message length was last calculated. Used by
     *  {@link #getByteLength()}
     **/
    protected transient int cachedByteLengthModCount = -1;
    
    
    /**
     *  If <tt>true</tt> then the message is modifiable. This is primarily 
     *  intended as a diagnostic tool for detecting concurrent modification.
     *
     *  @deprecated You really should not depend on this feature.
     **/
    public boolean modifiable = true;
    
    
    /**
     *  If <tt>LOG_MODIFICATIONS</tt> is <tt>true</tt> then this will contain 
     *  the history of modifications this message.
     *
     *  <p/><ul>
     *      <li>
     *      Values are {@link java.lang.Throwable} with the description field
     *      formatted as <code>timeInAbsoluteMillis : threadName</code>.
     *      </li>
     *  </ul>
     **/
    protected transient List modHistory;
    
    /**
     *  A ListIterator for MessageElements which also provides the ability to
     *  determine the namespace of the current message element. Message Elements
     *  are iterated in the order in which they were added to the Message.
     *
     *  <p/>This ListIterator returned is not synchronized with the message. If
     *  you modify the state of the Message, the iterator will throw
     *  ConcurrentModificationException when <code>next()</code> or
     *  <code>previous()</code> is called.
     **/
    public class ElementIterator implements ListIterator {
        
        /**
         * The elements being iterated.
         */
        ListIterator list;
        
        /**
         * The current element
         */
        element current = null;
        
        /**
         *  The modCount at the time when the iterator was created.
         **/
        transient int origModCount;
        
        /**
         * Intialize the iterator from a list iterator. The list iterator must
         * be an iterator of {@link element}.
         *
         * @param list The ListIterator we are managing.
         */
        ElementIterator( ListIterator list ) {
            origModCount = Message.this.getMessageModCount();
            this.list = list;
        }
        
        /**
         *  {@inheritDoc}
         **/
        public boolean hasNext() {
            if( origModCount != Message.this.getMessageModCount() ) {
                RuntimeException failure = new ConcurrentModificationException( Message.this + " concurrently modified. Iterator was made at mod " + origModCount );
                
                if (LOG.isEnabledFor(Level.ERROR)) {
                    LOG.error( Message.this + " concurrently modified. iterator mod=" + origModCount + " current mod=" + Message.this.getMessageModCount() + "\n" + getMessageModHistory(), failure );
                }
                
                throw failure;
            }
            
            return list.hasNext();
        }
        
        /**
         *  {@inheritDoc}
         **/
        public Object next() {
            if( origModCount != Message.this.getMessageModCount() ) {
                RuntimeException failure = new ConcurrentModificationException( Message.this + " concurrently modified. Iterator was made at mod " + origModCount );
                
                if (LOG.isEnabledFor(Level.ERROR)) {
                    LOG.error( Message.this + " concurrently modified. iterator mod=" + origModCount + " current mod=" + Message.this.getMessageModCount() + "\n" + getMessageModHistory(), failure );
                }
                
                throw failure;
            }
            
            current = (element) list.next();
            return current.element;
        }
        
        /**
         *  {@inheritDoc}
         **/
        public int nextIndex() {
            return list.nextIndex();
        }
        
        /**
         *  {@inheritDoc}
         **/
        public boolean hasPrevious() {
            if( origModCount != Message.this.getMessageModCount() ) {
                RuntimeException failure = new ConcurrentModificationException( Message.this + " concurrently modified. Iterator was made at mod " + origModCount );
                
                if (LOG.isEnabledFor(Level.ERROR)) {
                    LOG.error( Message.this + " concurrently modified. iterator mod=" + origModCount + " current mod=" + Message.this.getMessageModCount() + "\n" + getMessageModHistory(), failure );
                }
                
                throw failure;
            }
            
            return list.hasPrevious();
        }
        
        /**
         *  {@inheritDoc}
         **/
        public Object previous() {
            if( origModCount != Message.this.getMessageModCount() ) {
                RuntimeException failure = new ConcurrentModificationException( Message.this + " concurrently modified. Iterator was made at mod " + origModCount );
                
                if (LOG.isEnabledFor(Level.ERROR)) {
                    LOG.error( Message.this + " concurrently modified. iterator mod=" + origModCount + " current mod=" + Message.this.getMessageModCount() + "\n" + getMessageModHistory(), failure );
                }