FTP服务之Java操作FTP服务器下载文件的两种方式

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-netgroupId>
            <artifactId>commons-netartifactId>
            <version>3.10.0version>
        dependency>

2. 操作案例

1. 单文件下载

@Test
    public 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

   @Test
    public 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-netgroupId>
            <artifactId>commons-netartifactId>
            <version>3.10.0version>
        dependency>             
<dependency>
                    <groupId>cn.hutoolgroupId>
                    <artifactId>hutool-allartifactId>
                    <version>5.8.23version>
                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

@Test
    public 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);
    }


    @Test
    public 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);
    }