jxtamessagemessageelement.java

jxta_src_2.41b jxta 2.41b 最新版源码 from www.jxta.org

/************************************************************************
 *
 * $Id: JxtaMessageMessageElement.java,v 1.4 2006/01/06 20:46:20 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.impl.endpoint;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

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

import net.jxta.document.MimeMediaType;
import net.jxta.endpoint.Message;
import net.jxta.endpoint.MessageElement;
import net.jxta.endpoint.WireFormatMessageFactory;

/**
 * A Message Element using a JXTA Message as the element data
 *
 *  @see net.jxta.endpoint.Message
 *  @see net.jxta.endpoint.MessageElement
 **/
public class JxtaMessageMessageElement extends MessageElement {
    
    /**
     *  Log4J Logger
     **/
    private final static transient Logger LOG = Logger.getLogger( JxtaMessageMessageElement.class.getName() );
    
    /**
     *  The Message which is the data for this message element.
     **/
    protected final Message msg;
    
    /**
     *  A serialized form of the message.
     **/
    protected transient net.jxta.endpoint.WireFormatMessage serial;
    
    /**
     * Create a new Message Element. The contents of the provided message are 
     * <b>not</b> copied during construction.
     *
     * @param name Name of the MessageElement. May be the empty string ("") if
     * the MessageElement is not named.
     * @param type Type of the MessageElement. null is the same as specifying
     * the type "Application/Octet-stream".
     * @param msg A message which will be used as the element content for this
     * message.
     * @param sig optional message digest/digital signature elemnent or null if
     * no signature is desired.
     **/
    public JxtaMessageMessageElement( String name, MimeMediaType type, Message msg, MessageElement sig ) {
        super( name, type, sig );
        
        this.msg = msg;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public boolean equals( Object target ) {
        if( this == target ) {
            return true;
        }
        
        if( target instanceof MessageElement ) {
            if( !super.equals(target) ) {
                return false;
            }
            
            if( target instanceof JxtaMessageMessageElement ) {
                JxtaMessageMessageElement likeMe = (JxtaMessageMessageElement) target;
                
                return super.equals( likeMe ) & msg.equals( likeMe.msg );
            } else {
                // have to do a slow stream comparison.
                // XXX 20020615 [e-mail] the performance of this could be much improved.
                try {
                    MessageElement likeMe = (MessageElement) target;
                    
                    InputStream myStream = getStream();
                    InputStream itsStream = likeMe.getStream();
                    
                    int mine;
                    int its;
                    do {
                        mine = myStream.read();
                        its = itsStream.read();
                        
                        if( mine != its )
                            return false;       // content didn't match (includes EOF check).
                        
                    } while( -1 != mine );
                    
                    return true;
                } catch( IOException fatal ) {
                    if (LOG.isEnabledFor(Level.ERROR)) {
                        LOG.error( "MessageElements could not be compared.", fatal );
                    }
                    
                    IllegalStateException failure = new IllegalStateException( "MessageElements could not be compared." );
                    failure.initCause( fatal );
                    
                    throw failure;
                }
            }
        }
        
        return false; // not a message element
    }
    
    /**
     *  {@inheritDoc}
     **/
    public int hashCode() {
        int result = super.hashCode() *  6037 +   // a prime
        msg.hashCode();
        
        return (0 != result) ? result : 1;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public String toString( ) {
        throw new UnsupportedOperationException( "Cannot Generate String for this message element type." );
    }
    
    /**
     *  {@inheritDoc}
     **/
    public long getByteLength() {
        initSerial();
       
        return serial.getByteLength();
    }
    
    /**
     *  {@inheritDoc}
     **/
    public byte[] getBytes( boolean copy ) {
        initSerial();
       
        ByteArrayOutputStream baos = new ByteArrayOutputStream( (int) serial.getByteLength() );
        
        try {
            sendToStream( baos );
            
            baos.close();
        } catch ( IOException failed ) {
            throw new IllegalStateException( "failed to generate byte stream" );
        }
        
        return baos.toByteArray();
    }
    
    /**
     *  {@inheritDoc}
     **/
    public InputStream getStream() throws IOException {
        initSerial();
        
        return serial.getStream();
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void sendToStream( OutputStream sendTo ) throws IOException {
        initSerial();
        
        serial.sendToStream( sendTo );
    }
    
    /**
     *  Returns a copy of the message which backs this element.
     *
     *  @return Returns a copy of the message which backs this element.
     **/
    public Message getMessage() {
        return (Message) msg.clone();
    }
    
    /**
     *  Generates the serialized representation of the message.
     **/
    private synchronized void initSerial() {
        if( null == serial ) {
            serial = WireFormatMessageFactory.toWire( msg, type, null );
        }
    }
}