基于Apache FTP实现文件上传下载工具 ，上传文件时需要考虑以下问题（实例是续传功能）：

（1）、 FTP服务器是否存在改目录，如果不存在目录则需要创建目录。

（2）、判断上传文件是否已经存在，如果存在是需要删除后再上传还是续传。

1、上传或下载状态的枚举类：

package com.scengine.wtms.utils.ftp; public enum UploadStatus { File_Exits(0), Create_Directory_Success(1), Create_Directory_Fail(2), Upload_From_Break_Success(3), Upload_From_Break_Faild(4), Download_From_Break_Success(5), Download_From_Break_Faild(6), Upload_New_File_Success(7), Upload_New_File_Failed(8), Delete_Remote_Success(9), Delete_Remote_Faild(10),Remote_Bigger_Local(11),Remote_smaller_locall(12); private int status; public int getStatus() { return status; } public void setStatus(int status) { this.status = status; } UploadStatus(int status) { this.status = status; } }

2、工具类代码：

package com.scengine.wtms.utils.ftp; 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(); /** * 对象构造 设置将过程中使用到的命令输出到控制台 */ public ContinueFTP() { 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 */ @SuppressWarnings("resource") 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 */ @SuppressWarnings("resource") 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("192.168.1.200", 21, "duser", "HTPDuserXP32"); System.out.println(myFtp.upload("C:UsersAdministratorDesktopswing.drawer.jar", "/jars/swing.drawer.jar")); myFtp.disconnect(); } catch (IOException e) { System.out.println("连接FTP出错：" + e.getMessage()); } } }

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