Smack/source/org/jivesoftware/smack/SmackConfiguration.java

/**
* $RCSfile$
* $Revision$
* $Date$
*
* Copyright (C) 2002-2003 Jive Software. All rights reserved.
* ====================================================================
* The Jive Software License (based on Apache Software License, Version 1.1)
*
* 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
*        Jive Software (http://www.jivesoftware.com)."
*    Alternately, this acknowledgment may appear in the software itself,
*    if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Smack" and "Jive Software" must not be used to
*    endorse or promote products derived from this software without
*    prior written permission. For written permission, please
*    contact webmaster@jivesoftware.com.
*
* 5. Products derived from this software may not be called "Smack",
*    nor may "Smack" appear in their name, without prior written
*    permission of Jive Software.
*
* 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 JIVE SOFTWARE 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.
* ====================================================================
*/

package org.jivesoftware.smack;

import java.io.*;
import java.net.*;
import java.util.*;

import org.xmlpull.v1.*;

/**
 * Represents the configuration of Smack. The configuration is used for:
 * <ul>
 *      <li> Initializing classes by loading them at start-up.
 *      <li> Getting the current Smack version.
 * </ul>
 * 
 * @author Gaston Dombiak
 */
public final class SmackConfiguration {

    private static String versionNumber;

    private SmackConfiguration() {
    }

    /**
     * Loads the configuration from the smack.configuration file.<p>
     * 
     * So far this means that:
     * 1) a set of classes will be loaded in order to execute their static init block
     * 2) retrieve and set the current Smack release
     *
     */
    static void init() {
        try {
            // Get an array of class loaders to try loading the providers files from.
            ClassLoader[] classLoaders = getClassLoaders();
            for (int i = 0; i < classLoaders.length; i++) {
                Enumeration enum = classLoaders[i].getResources("META-INF/smack.configuration");
                while (enum.hasMoreElements()) {
                    URL url = (URL) enum.nextElement();
                    InputStream systemStream = null;
                    try {
                        systemStream = url.openStream();
                        XmlPullParserFactory factory =
                            XmlPullParserFactory.newInstance(
                                "org.xmlpull.mxp1.MXParserFactory",
                                null);
                        factory.setNamespaceAware(true);
                        XmlPullParser parser = factory.newPullParser();
                        parser.setInput(systemStream, "UTF-8");
                        int eventType = parser.getEventType();
                        do {
                            if (eventType == XmlPullParser.START_TAG) {
                                if (parser.getName().equals("className")) {
                                    String className = parser.nextText();
                                    // Attempt to load the class so that the class can get initialized
                                    try {
                                        Class provider = Class.forName(className);
                                    }
                                    catch (ClassNotFoundException cnfe) {
                                        cnfe.printStackTrace();
                                    }
                                }
                                else if (parser.getName().equals("versionNumber")) {
                                    versionNumber = parser.nextText();
                                }
                            }
                            eventType = parser.next();
                        }
                        while (eventType != XmlPullParser.END_DOCUMENT);
                    }
                    finally {
                        try {
                            systemStream.close();
                        }
                        catch (Exception e) {
                        }
                    }
                }
            }
        }
        catch (Exception e) {
        }
    }
    
    /**
     * Returns the current Smack release version. The version number value
     * gets loaded from the smack.configuration file at system startup.
     * 
     * @return the current Smack release version number
     */
    public static String getVersionNumber() {
        return versionNumber;
    }

    /**
     * Returns an array of class loaders to load resources from.
     *
     * @return an array of ClassLoader instances.
     */
    private static ClassLoader[] getClassLoaders() {
        ClassLoader[] classLoaders = new ClassLoader[3];
        classLoaders[0] = new SmackConfiguration().getClass().getClassLoader();
        classLoaders[1] = Thread.currentThread().getContextClassLoader();
        classLoaders[2] = ClassLoader.getSystemClassLoader();
        return classLoaders;
    }
}