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FTP服务之Java操作FTP服务器下载文件的两种方式

注意：如果fpt服务中没有建立目录， 则默认文件目录为根目录也即/,否则按具体目录进行操作，如: /demo
FTP服务搭建查看博文 FTP服务之WindowsServer2019中搭建私有FTP服务器

1. 使用Apache commons-net工具包

1. 引入commons-net依赖

<dependency><groupId>commons-net</groupId><artifactId>commons-net</artifactId><version>3.10.0</version></dependency>

2. 操作案例

1. 单文件下载

@Testpublic void downLoadOne() {String server = "192.168.31.252";int port = 21;String user = "anonymous";String password = "";String remoteFile = "/demo/xxx说明书.pdf";String localFile = "F:\\ftpDownlaod\\newAAA.pdf";FTPClient ftpClient = new FTPClient();OutputStream outputStream = null;try {ftpClient.connect(server, port);ftpClient.login(user, password);ftpClient.enterLocalPassiveMode();outputStream = Files.newOutputStream(Paths.get(localFile));// ftp默认使用ISO-8859-1编码格式,所以这里需要转换为ISO-8859-1，“解决文件名为中文时，下载后为空文件的问题”String remoteFileName = new String(remoteFile.getBytes("GBK"), StandardCharsets.ISO_8859_1);ftpClient.retrieveFile(remoteFileName, outputStream);} catch (IOException ex) {System.out.println("DownLoad Error: " + ex.getMessage());ex.printStackTrace();} finally {try {if (outputStream != null) {outputStream.close();}ftpClient.disconnect();} catch (IOException ex) {ex.printStackTrace();}}}

2. 切换到指定目录批量下载文件

   @Testpublic void batchDownLoadFileFromFtp() {FTPClient client = new FTPClient();try {//设置主机与端口client.connect("192.168.31.252", 21);//设置用户名及密码，这里以匿名用户登录为例，根据需求改为自己的用户名及密码client.login("anonymous", "");System.out.println("FTP服务器文件编码===>>" + client.getControlEncoding());int reply = client.getReplyCode();if (!FTPReply.isPositiveCompletion(reply)) {client.disconnect();System.out.println("Login Error,Please check if your username or password is correct");return;}client.setControlEncoding("GBK");System.out.println("设置后的文件编码：" + client.getControlEncoding());client.enterLocalPassiveMode();//切换到demo目录下client.changeWorkingDirectory("demo");System.out.println("---------------------------------------");String[] names;names = client.listNames();for (String name : names) {System.out.println(name);}System.out.println("ftp服务中,demo目录中的所有文件:" + Arrays.toString(names));System.out.println("---------------------------------------");FTPFile f = client.listFiles()[0];System.out.println("getLink===>" + f.getLink());//切换到根目录下client.changeWorkingDirectory("/");String path = "/demo";client.setBufferSize(1024);client.setFileType(FTP.BINARY_FILE_TYPE);client.enterLocalPassiveMode();//切换到demo目录下获取此目录中所有的文件，并进行一个下载client.changeWorkingDirectory(path);FTPFile[] fs = client.listFiles();for (FTPFile ff : fs) {String outFileName = ff.getName();System.out.println(outFileName);//本地目录文件不需要编码File localFile = new File("F:\\ftpDownlaod\\" + ff.getName());OutputStream fos = Files.newOutputStream(localFile.toPath());// ftp默认使用ISO-8859-1编码格式,所以这里需要转换为ISO-8859-1，“解决文件名为中文时，下载后为空文件的问题”String localFileName = new String(ff.getName().getBytes("GBK"), StandardCharsets.ISO_8859_1);client.retrieveFile(localFileName, fos);fos.close();}} catch (Exception e) {e.printStackTrace();} finally {try {client.disconnect();} catch (IOException e) {e.printStackTrace();}}}

2. 使用Hutool工具

Hutool对FTP客户端基于Apache Commons Net做了进一步的封装。

文档地址：扩展（Hutool-extra） - FTP封装-Ftp

1. 引入依赖

<dependency><groupId>commons-net</groupId><artifactId>commons-net</artifactId><version>3.10.0</version></dependency>             
<dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>5.8.23</version></dependency>

2. 操作案例

1. 文件下载

目前存在的问题： 如果文件名称是中文，则下载后的文件大小为0

@Testpublic void ftpServerTestByAnonymousOne() {Ftp ftp = new Ftp("192.168.31.252", 21);String downLoadPath = "/demo";String fileName = "demo.pdf";String outputPath = "F:\\ftpDownlaod";ftp.download(downLoadPath, fileName, new File(outputPath));//关闭连接try {ftp.close();} catch (IOException e) {throw new RuntimeException(e);}//FtpUtil.downloadFile(host, port, user, password, remotePath, localPath);}@Testpublic void ftpServerTestByAnonymousTwo() throws UnsupportedEncodingException {Ftp ftp = new Ftp("192.168.31.252", 21, "anonymous", "", StandardCharsets.UTF_8);String downLoadPath = "/demo";String fileName = "数据迁移最佳实践.pdf";//String remoteFileName = new String(fileName.getBytes("utf-8"),"ISO-8859-1");String outputPath = "F:\\ftpDownlaod\\xxx.pdf";ftp.download(downLoadPath, fileName, new File(outputPath));//关闭连接try {ftp.close();} catch (IOException e) {throw new RuntimeException(e);}//FtpUtil.downloadFile(host, port, user, password, remotePath, localPath);}