JAVA实现FTP断点上传的方法

本文实例讲述了java实现ftp断点上传的方法。分享给大家供大家参考。具体分析如下：

这里主要使用apache中的net包来实现。网址http://commons.apache.org/net/。具体包的下载和api文档请看官网。 断点上传就是在上传的过程中设置传输的起始位置。并设置二进制传输。

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()); 
     } 
   } 
}

希望本文所述对大家的java程序设计有所帮助。