org/sonews/daemon/CommandSelector.java
author cli
Mon, 24 Aug 2009 14:40:37 +0200
changeset 21 4b2c8bedb094
parent 15 f2293e8566f5
child 26 407c428adb5b
permissions -rw-r--r--
Refactoring in CommandSelector to allow manually loading of plugins.
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/*
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 *   SONEWS News Server
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 *   see AUTHORS for the list of contributors
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 *
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 *   This program is free software: you can redistribute it and/or modify
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 *   it under the terms of the GNU General Public License as published by
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 *   the Free Software Foundation, either version 3 of the License, or
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 *   (at your option) any later version.
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 *
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 *   This program is distributed in the hope that it will be useful,
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 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
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 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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 *   GNU General Public License for more details.
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 *
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 *   You should have received a copy of the GNU General Public License
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 *   along with this program.  If not, see <http://www.gnu.org/licenses/>.
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 */
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package org.sonews.daemon;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.concurrent.ConcurrentHashMap;
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import org.sonews.daemon.command.Command;
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import org.sonews.daemon.command.UnsupportedCommand;
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import org.sonews.util.Log;
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import org.sonews.util.io.Resource;
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/**
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 * Selects the correct command processing class.
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 * @author Christian Lins
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 * @since sonews/1.0
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 */
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public class CommandSelector
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{
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  private static Map<Thread, CommandSelector> instances
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    = new ConcurrentHashMap<Thread, CommandSelector>();
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  private static Map<String, Class<?>> commandClassesMapping
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    = new ConcurrentHashMap<String, Class<?>>();
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  static
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  {
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    String[] classes = Resource.getAsString("helpers/commands.list", true).split("\n");
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    for(String className : classes)
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    {
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      if(className.charAt(0) == '#')
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      {
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        // Skip comments
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        continue;
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      }
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      try
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      {
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        addCommandHandler(className);
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      }
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      catch(ClassNotFoundException ex)
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      {
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        Log.get().warning("Could not load command class: " + ex);
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      }
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      catch(InstantiationException ex)
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      {
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        Log.get().severe("Could not instantiate command class: " + ex);
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      }
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      catch(IllegalAccessException ex)
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      {
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        Log.get().severe("Could not access command class: " + ex);
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      }
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    }
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  }
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  public static void addCommandHandler(String className)
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    throws ClassNotFoundException, InstantiationException, IllegalAccessException
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  {
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    Class<?> clazz = Class.forName(className);
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    Command cmd = (Command)clazz.newInstance();
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    String[] cmdStrs = cmd.getSupportedCommandStrings();
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    for (String cmdStr : cmdStrs)
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    {
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      commandClassesMapping.put(cmdStr, clazz);
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    }
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  }
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  public static CommandSelector getInstance()
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  {
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    CommandSelector csel = instances.get(Thread.currentThread());
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    if(csel == null)
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    {
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      csel = new CommandSelector();
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      instances.put(Thread.currentThread(), csel);
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    }
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    return csel;
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  }
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  private Map<String, Command> commandMapping = new HashMap<String, Command>();
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  private Command              unsupportedCmd = new UnsupportedCommand();
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  private CommandSelector()
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  {}
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  public Command get(String commandName)
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  {
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    try
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    {
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      commandName = commandName.toUpperCase();
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      Command cmd = this.commandMapping.get(commandName);
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      if(cmd == null)
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      {
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        Class<?> clazz = commandClassesMapping.get(commandName);
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        if(clazz == null)
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        {
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          cmd = this.unsupportedCmd;
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        }
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        else
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        {
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          cmd = (Command)clazz.newInstance();
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          this.commandMapping.put(commandName, cmd);
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        }
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      }
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      else if(cmd.isStateful())
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      {
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        cmd = cmd.getClass().newInstance();
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      }
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      return cmd;
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    }
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    catch(Exception ex)
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    {
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      ex.printStackTrace();
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      return this.unsupportedCmd;
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    }
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  }
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}