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。