用java写的ftp服务器程序

				// $Id: PASS.java 306757 2005-10-06 11:33:33 +0530 (Thu, 06 Oct 2005) rana_b $
				/*
				 * Copyright 2004 The Apache Software Foundation
				 *
				 * Licensed under the Apache License, Version 2.0 (the "License");
				 * you may not use this file except in compliance with the License.
				 * You may obtain a copy of the License at
				 *
				 *     http://www.apache.org/licenses/LICENSE-2.0
				 *
				 * Unless required by applicable law or agreed to in writing, software
				 * distributed under the License is distributed on an "AS IS" BASIS,
				 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
				 * See the License for the specific language governing permissions and
				 * limitations under the License.
				 */
				package org.apache.ftpserver.command;
				
				import java.io.IOException;
				
				import org.apache.commons.logging.Log;
				import org.apache.ftpserver.Command;
				import org.apache.ftpserver.DirectoryLister;
				import org.apache.ftpserver.FtpRequestImpl;
				import org.apache.ftpserver.FtpWriter;
				import org.apache.ftpserver.RequestHandler;
				import org.apache.ftpserver.ftplet.FileSystemManager;
				import org.apache.ftpserver.ftplet.FileSystemView;
				import org.apache.ftpserver.ftplet.FtpException;
				import org.apache.ftpserver.ftplet.Ftplet;
				import org.apache.ftpserver.ftplet.FtpletEnum;
				import org.apache.ftpserver.ftplet.User;
				import org.apache.ftpserver.ftplet.UserManager;
				import org.apache.ftpserver.interfaces.IConnectionManager;
				import org.apache.ftpserver.interfaces.IFtpConfig;
				import org.apache.ftpserver.interfaces.IFtpStatistics;
				import org.apache.ftpserver.usermanager.BaseUser;
				
				/**
				 * PASS <SP>  <CRLF>
				 *
				 * The argument field is a Telnet string specifying the user's
				 * password.  This command must be immediately preceded by the
				 * user name command.
				 * 
				 * @author Rana Bhattacharyya
				 */
				public 
				class PASS implements Command {
				    
				    /**
				     * Execute command.
				     */
				    public void execute(RequestHandler handler, 
				                        FtpRequestImpl request, 
				                        FtpWriter out) throws IOException, FtpException {
				    
				        boolean bSuccess = false;
				        IFtpConfig fconfig = handler.getConfig();
				        Log log = fconfig.getLogFactory().getInstance(getClass());
				        IConnectionManager conManager = fconfig.getConnectionManager();
				        IFtpStatistics stat = (IFtpStatistics)fconfig.getFtpStatistics();
				        try {
				            
				            // reset state variables
				            request.resetState();
				            
				            // argument check
				            String password = request.getArgument();
				            if(password == null) {
				                out.send(501, "PASS", null);
				                return; 
				            }
				            
				            // check user name
				            User user = request.getUser();
				            String userName = user.getName();
				            if(userName == null) {
				                out.send(503, "PASS", null);
				                return;
				            }
				            
				            // already logged-in
				            if(request.isLoggedIn()) {
				                out.send(202, "PASS", null);
				                bSuccess = true;
				                return;
				            }
				            
				            // anonymous login limit check
				            boolean bAnonymous = userName.equals("anonymous");
				            int currAnonLogin = stat.getCurrentAnonymousLoginNumber();
				            int maxAnonLogin = conManager.getMaxAnonymousLogins();
				            if( bAnonymous && (currAnonLogin >= maxAnonLogin) ) {
				                out.send(421, "PASS.anonymous", null);
				                return;
				            }
				            
				            // login limit check
				            int currLogin = stat.getCurrentLoginNumber();
				            int maxLogin = conManager.getMaxLogins();
				            if(currLogin >= maxLogin) {
				                out.send(421, "PASS.login", null);
				                return;
				            }
				            
				            // authenticate user
				            UserManager userManager = fconfig.getUserManager();
				            try {
				                if(bAnonymous) {
				                    bSuccess = userManager.doesExist("anonymous");
				                }
				                else {
				                    bSuccess = userManager.authenticate(userName, password);
				                }
				            }
				            catch(Exception ex) {
				                bSuccess = false;
				                log.warn("PASS.execute()", ex);
				            }
				            if(!bSuccess) {
				                log.warn("Login failure - " + userName);
				                out.send(530, "PASS", userName);
				                return;
				            }
				            
				            // populate user information
				            try {
				                populateUser(handler, userName);
				            }
				            catch(FtpException ex) {
				                bSuccess = false;
				            }
				            if(!bSuccess) {
				                out.send(530, "PASS", userName);
				                return;
				            }
				            
				            // everything is fine - send login ok message
				            out.send(230, "PASS", userName);
				            if(bAnonymous) {
				                log.info("Anonymous login success - " + password);
				            }
				            else {
				                log.info("Login success - " + userName);
				            }
				            
				            // update different objects
				            FileSystemManager fmanager = fconfig.getFileSystemManager(); 
				            FileSystemView fsview = fmanager.createFileSystemView(user);
				            handler.setDirectoryLister(new DirectoryLister(fsview));
				            request.setLogin(fsview);
				            stat.setLogin(handler);
				            
				            // call Ftplet.onLogin() method
				            Ftplet ftpletContainer = fconfig.getFtpletContainer();
				            FtpletEnum ftpletRet = ftpletContainer.onLogin(request, out);
				            if(ftpletRet == FtpletEnum.RET_DISCONNECT) {
				                fconfig.getConnectionManager().closeConnection(handler);
				                return;
				            }    
				        }
				        finally {
				            
				            // if login failed - close connection
				            if(!bSuccess) {
				                conManager.closeConnection(handler);
				            }
				        }
				    }
				
				    /**
				     * Populate user.
				     */
				    private void populateUser(RequestHandler handler,
				                              String login) throws FtpException {
				        
				        User user = handler.getConfig().getUserManager().getUserByName(login);
				        if(user == null) {
				            throw new FtpException(login + " : does not exist.");
				        }
				        
				        BaseUser reqUser = (BaseUser)handler.getRequest().getUser();
				        reqUser.setName(user.getName());
				        reqUser.setEnabled(user.getEnabled());
				        reqUser.setHomeDirectory(user.getHomeDirectory());
				        reqUser.setMaxDownloadRate(user.getMaxDownloadRate());
				        reqUser.setMaxDownloadRate(user.getMaxDownloadRate());
				        reqUser.setMaxIdleTime(user.getMaxIdleTime());
				        reqUser.setWritePermission(user.getWritePermission());
				    }
				}