/* * This file is part of "The Java Telnet Application". * * This 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. * * "The Java Telnet Application" 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 this software; see the file COPYING.  If not, write to the * Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 02111-1307, USA. */package de.mud.jta;import java.util.Properties;import java.util.Vector;import java.util.Enumeration;import java.lang.reflect.Constructor;/** * The plugin loader tries to load the plugin by name and returns a * corresponding plugin object. It takes care of connecting filter * plugins * <P> * <B>Maintainer:</B> Matthias L. Jugel * * @version $Id: PluginLoader.java,v 2.2 2000/02/09 09:33:54 leo Exp $ * @author Matthias L. Jugel, Marcus Mei遪er */public class PluginLoader implements PluginBus {  /** holds the current version id */  public final static String ID = "$Id: PluginLoader.java,v 2.2 2000/02/09 09:33:54 leo Exp $";  private final static int debug = 0;  /** the path to standard plugins */  private Vector PATH = null;  /** holds all the filters */  private Vector filter = new Vector();  /**   * Create new plugin loader and set up with default plugin path.   */  public PluginLoader() {    this(null);  }  /**   * Create new plugin loader and set up with specified plugin path.   * @param path the default search path for plugins   */  public PluginLoader(Vector path) {    if(path == null) {      PATH = new Vector();      PATH.addElement("de.mud.jta.plugin");     } else      PATH = path;  }  /**   * Add a new plugin to the system and register the plugin load as its   * communication bus. If the plugin is a filter plugin and if it is   * not the first filter the last added filter will be set as its filter   * source.   * @param name the string name of the plugin   * @return the newly created plugin or null in case of an error   */  public Plugin addPlugin(String name, String id) {    Plugin plugin = null;    // cycle through the PATH to load plugin    Enumeration path = PATH.elements();    while(plugin == null && path.hasMoreElements())      plugin = loadPlugin((String)path.nextElement(), name, id);    // if it was not found, try without a path as a last resort    if(plugin == null)      plugin = loadPlugin(null, name, id);    // nothing found, tell the user    if(plugin == null) {      System.err.println("plugin loader: plugin '"+name+"' was not found!");      return null;    }    // configure the filter plugins    if(plugin instanceof FilterPlugin) {      if(filter.size() > 0)        ((FilterPlugin)plugin)          .setFilterSource((FilterPlugin)filter.lastElement());      filter.addElement(plugin);    }    return plugin;  }  private Plugin loadPlugin(String path, String name, String id) {    Plugin plugin = null;    String fullClassName = (path == null) ? name : path + "." + name;    // load the plugin by name and instantiate it    try {      Class c = Class.forName(fullClassName);      Constructor cc = c.getConstructor(new Class[] { PluginBus.class,                                                       String.class });      plugin = (Plugin)cc.newInstance(new Object[] { this, id });      return plugin;    } catch(ClassNotFoundException ce) {      if(debug > 0)        System.err.println("plugin loader: plugin not found: "+fullClassName);    } catch(Exception e) {      System.err.println("plugin loader: can't load plugin: "+fullClassName);      e.printStackTrace();    }    return null;  }  /** holds the plugin listener we serve */  private Vector listener = new Vector();  /**   * Register a new plugin listener.   */  public void registerPluginListener(PluginListener l) {    listener.addElement(l);  }  /**   * Implementation of the plugin bus. Broadcast a message to all   * listeners we know of. The message takes care that the right   * methods are called in the  listeners.   * @param message the plugin message to be sent   * @return the answer to the sent message   */  public Object broadcast(PluginMessage message) {    if(debug>0) System.err.println("broadcast("+message+")");    if(message == null || listener == null)      return null;    Enumeration e = listener.elements();    Object res = null;    while(res == null && e.hasMoreElements())      res = message.firePluginMessage((PluginListener)e.nextElement());    return res;  }}