JAVA实现FTP断点上传的方法

import java.io.File; 
import java.io.FileInputStream; 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.io.InputStream; 
import java.io.OutputStream; 
import java.io.PrintWriter; 
import org.apache.commons.net.PrintCommandListener; 
import org.apache.commons.net.ftp.FTP; 
import org.apache.commons.net.ftp.FTPClient; 
import org.apache.commons.net.ftp.FTPFile; 
import org.apache.commons.net.ftp.FTPReply; 
public class ContinueFTP { 
   private FTPClient ftpClient = new FTPClient(); 
   public ContinueFTP(){ 
     //设置将过程中使用到的命令输出到控制台 
     this.ftpClient.addProtocolCommandListener(new PrintCommandListener(new PrintWriter(System.out))); 
   } 
   /** 
   * java编程中用于连接到FTP服务器 
   * @param hostname 主机名 
   * @param port 端口 
   * @param username 用户名 
   * @param password 密码 
   * @return 是否连接成功 
   * @throws IOException 
   */ 
   public boolean connect(String hostname,int port,String username,String password) throws IOException{ 
     ftpClient.connect(hostname, port); 
     if(FTPReply.isPositiveCompletion(ftpClient.getReplyCode())){ 
       if(ftpClient.login(username, password)){ 
         return true; 
       } 
     } 
     disconnect(); 
     return false; 
   } 
   /** 
   * 从FTP服务器上下载文件 
   * @param remote 远程文件路径 
   * @param local 本地文件路径 
   * @return 是否成功 
   * @throws IOException 
   */ 
   public boolean download(String remote,String local) throws IOException{ 
     ftpClient.enterLocalPassiveMode(); 
     ftpClient.setFileType(FTP.BINARY_FILE_TYPE); 
     boolean result; 
     File f = new File(local); 
     FTPFile[] files = ftpClient.listFiles(remote); 
     if(files.length != 1){ 
       System.out.println("远程文件不唯一"); 
       return false; 
     } 
     long lRemoteSize = files[0].getSize(); 
     if(f.exists()){ 
       OutputStream out = new FileOutputStream(f,true); 
       System.out.println("本地文件大小为:"+f.length()); 
       if(f.length() >= lRemoteSize){ 
         System.out.println("本地文件大小大于远程文件大小，下载中止"); 
         return false; 
       } 
       ftpClient.setRestartOffset(f.length()); 
       result = ftpClient.retrieveFile(remote, out); 
       out.close(); 
     }else { 
       OutputStream out = new FileOutputStream(f); 
       result = ftpClient.retrieveFile(remote, out); 
       out.close(); 
     } 
     return result; 
   } 
   /** 
   * 上传文件到FTP服务器，支持断点续传 
   * @param local 本地文件名称，绝对路径 
   * @param remote 远程文件路径，使用/home/directory1/subdirectory/file.ext 按照Linux上的路径指定方式，支持多级目录嵌套，支持递归创建不存在的目录结构 
   * @return 上传结果 
   * @throws IOException 
   */ 
   public UploadStatus upload(String local,String remote) throws IOException{ 
     //设置PassiveMode传输 
     ftpClient.enterLocalPassiveMode(); 
     //设置以二进制流的方式传输 
     ftpClient.setFileType(FTP.BINARY_FILE_TYPE); 
     UploadStatus result; 
     //对远程目录的处理 
     String remoteFileName = remote; 
     if(remote.contains("/")){ 
       remoteFileName = remote.substring(remote.lastIndexOf("/")+1); 
       String directory = remote.substring(0,remote.lastIndexOf("/")+1); 
       if(!directory.equalsIgnoreCase("/")&&!ftpClient.changeWorkingDirectory(directory)){ 
         //如果远程目录不存在，则递归创建远程服务器目录 
         int start=0; 
         int end = 0; 
         if(directory.startsWith("/")){ 
           start = 1; 
         }else{ 
           start = 0; 
         } 
         end = directory.indexOf("/",start); 
         while(true){ 
           String subDirectory = remote.substring(start,end);
           if(!ftpClient.changeWorkingDirectory(subDirectory)){ 
             if(ftpClient.makeDirectory(subDirectory)){ 
               ftpClient.changeWorkingDirectory(subDirectory); 
             }else { 
               System.out.println("创建目录失败"); 
               return UploadStatus.Create_Directory_Fail;
             } 
           } 
           start = end + 1; 
           end = directory.indexOf("/",start); 
           //检查所有目录是否创建完毕 
           if(end <= start){ 
             break; 
           } 
         } 
       } 
     } 
     //检查远程是否存在文件 
     FTPFile[] files = ftpClient.listFiles(remoteFileName); 
     if(files.length == 1){ 
       long remoteSize = files[0].getSize(); 
       File f = new File(local); 
       long localSize = f.length(); 
       if(remoteSize==localSize){ 
         return UploadStatus.File_Exits; 
       }else if(remoteSize > localSize){ 
         return UploadStatus.Remote_Bigger_Local; 
       } 
       //尝试移动文件内读取指针,实现断点续传 
       InputStream is = new FileInputStream(f); 
       if(is.skip(remoteSize)==remoteSize){ 
         ftpClient.setRestartOffset(remoteSize); 
         if(ftpClient.storeFile(remote, is)){ 
           return UploadStatus.Upload_From_Break_Success; 
         } 
       } 
       //如果断点续传没有成功，则删除服务器上文件，重新上传 
       if(!ftpClient.deleteFile(remoteFileName)){ 
         return UploadStatus.Delete_Remote_Faild; 
       } 
       is = new FileInputStream(f); 
       if(ftpClient.storeFile(remote, is)){   
         result = UploadStatus.Upload_New_File_Success; 
       }else{ 
         result = UploadStatus.Upload_New_File_Failed; 
       } 
       is.close(); 
     }else { 
       InputStream is = new FileInputStream(local); 
       if(ftpClient.storeFile(remoteFileName, is)){ 
         result = UploadStatus.Upload_New_File_Success; 
       }else{ 
         result = UploadStatus.Upload_New_File_Failed; 
       } 
       is.close(); 
     } 
     return result; 
   } 
   /** 
   * 断开与远程服务器的连接 
   * @throws IOException 
   */ 
   public void disconnect() throws IOException{ 
     if(ftpClient.isConnected()){ 
       ftpClient.disconnect(); 
     } 
   } 
   public static void main(String[] args) { 
     ContinueFTP myFtp = new ContinueFTP(); 
     try { 
       myFtp.connect("192.168.21.171", 21, "test", "test"); 
       System.out.println(myFtp.upload("E:\\VP6.flv", "/MIS/video/VP6.flv")); 
       myFtp.disconnect(); 
     } catch (IOException e) { 
       System.out.println("连接FTP出错："+e.getMessage()); 
     } 
   } 
}