messagetutorial.java

jxta的例子

/*
 * Copyright (c) 2006-2007 Sun Microsystems, Inc.  All rights reserved.
 *  
 *  The Sun Project JXTA(TM) Software License
 *  
 *  Redistribution and use in source and binary forms, with or without 
 *  modification, are permitted provided that the following conditions are met:
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 *  1. Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
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 *     developed by Sun Microsystems, Inc. for JXTA(TM) technology." 
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 *  http://www.jxta.org.
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package tutorial.message;

import net.jxta.document.AdvertisementFactory;
import net.jxta.document.MimeMediaType;
import net.jxta.document.StructuredDocumentFactory;
import net.jxta.document.XMLDocument;
import net.jxta.endpoint.ByteArrayMessageElement;
import net.jxta.endpoint.Message;
import net.jxta.endpoint.Message.ElementIterator;
import net.jxta.endpoint.MessageElement;
import net.jxta.endpoint.StringMessageElement;
import net.jxta.endpoint.TextDocumentMessageElement;
import net.jxta.endpoint.WireFormatMessage;
import net.jxta.endpoint.WireFormatMessageFactory;
import net.jxta.id.IDFactory;
import net.jxta.peergroup.PeerGroupID;
import net.jxta.pipe.PipeService;
import net.jxta.protocol.PipeAdvertisement;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.RandomAccessFile;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

/**
 * A simple and re-usable example of manipulating JXATA Messages. Included in
 * this tutorial are:
 * <p/>
 * <ul>
 * <li>Adding and reading {@code String}, {@code int} and {@code long} with Message elements.</li>
 * <li>Adding and reading Java {@code Object} with Message Elements.
 * <li>Adding and reading byte arrays with Message Elements.</li>
 * <li>Adding and reading JXTA Advertisements with Message Elements.</li>
 * <li>Compressing message element content with gzip.</li>
 * </ul>
 */
public class MessageTutorial {
    private final static MimeMediaType GZIP_MEDIA_TYPE = new MimeMediaType("application/gzip").intern();

    /**
     * Adds a String to a Message as a StringMessageElement
     *
     * @param message   The message to add to
     * @param nameSpace The namespace of the element to add. a null value assumes default namespace.
     * @param elemName  Name of the Element.
     * @param string    The string to add
     */
    public static void addStringToMessage(Message message, String nameSpace, String elemName, String string) {
        message.addMessageElement(nameSpace, new StringMessageElement(elemName, string, null));
    }

    /**
     * Adds a long to a message
     *
     * @param message   The message to add to
     * @param nameSpace The namespace of the element to add. a null value assumes default namespace.
     * @param elemName  Name of the Element.
     * @param data      The feature to be added to the LongToMessage attribute
     */
    public static void addLongToMessage(Message message, String nameSpace, String elemName, long data) {
        message.addMessageElement(nameSpace, new StringMessageElement(elemName, Long.toString(data), null));
    }

    /**
     * Adds a int to a message
     *
     * @param message   The message to add to
     * @param nameSpace The namespace of the element to add. a null value assumes default namespace.
     * @param elemName  Name of the Element.
     * @param data      The feature to be added to the IntegerToMessage attribute
     */
    public static void addIntegerToMessage(Message message, String nameSpace, String elemName, int data) {
        message.addMessageElement(nameSpace, new StringMessageElement(elemName, Integer.toString(data), null));
    }

    /**
     * Adds an byte array to a message
     *
     * @param message   The message to add to
     * @param nameSpace The namespace of the element to add. a null value assumes default namespace.
     * @param elemName  Name of the Element.
     * @param data      the byte array
     * @param compress  indicates whether to use GZIP compression
     * @throws IOException if an io error occurs
     */
    public static void addByteArrayToMessage(Message message, String nameSpace, String elemName, byte[] data, boolean compress) throws IOException {
        byte[] buffer = data;
        MimeMediaType mimeType = MimeMediaType.AOS;

        if (compress) {
            ByteArrayOutputStream outStream = new ByteArrayOutputStream();
            GZIPOutputStream gos = new GZIPOutputStream(outStream);

            gos.write(data, 0, data.length);
            gos.finish();
            gos.close();
            buffer = outStream.toByteArray();
            mimeType = GZIP_MEDIA_TYPE;
        }
        message.addMessageElement(nameSpace, new ByteArrayMessageElement(elemName, mimeType, buffer, null));
    }

    /**
     * Adds an Object to message within the specified name space and with the specified element name
     * @param message   the message to add the object to
     * @param nameSpace the name space to add the object under
     * @param elemName  the given element name
     * @param object    the object
     * @throws IOException if an io error occurs
     */
    public static void addObjectToMessage(Message message, String nameSpace, String elemName, Object object) throws IOException {
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(bos);

        oos.writeObject(object);
        oos.close();
        bos.close();
        addByteArrayToMessage(message, nameSpace, elemName, bos.toByteArray(), false);
    }

    /**
     * Returns a String from a message
     *
     * @param message   The message to retrieve from
     * @param nameSpace The namespace of the element to get.
     * @param elemName  Name of the Element.
     * @return The string value or {@code null} if there was no element matching the specified name.
     */
    public static String getStringFromMessage(Message message, String nameSpace, String elemName) {
        MessageElement me = message.getMessageElement(nameSpace, elemName);

        if (null != me) {
            return me.toString();
        } else {
            return null;
        }
    }

    /**
     * Returns an long from a message
     *
     * @param message   The message to retrieve from
     * @param nameSpace The namespace of the element to get.
     * @param elemName  Name of the Element.