如何将 FTP 服务器上的文件复制到 Java 中同一服务器上的目录？

Question

我正在使用 Apache Commons FTP 上传文件。在上传之前，我想检查服务器上是否已经存在该文件，并将其备份到同一台服务器上的备份目录中。

有谁知道如何将文件从 FTP 服务器复制到同一服务器上的备份目录？

 public static void uploadWithCommonsFTP(File fileToBeUpload){
    FTPClient f = new FTPClient();
    FTPFile backupDirectory;
    try {
        f.connect(server.getServer());
        f.login(server.getUsername(), server.getPassword());
        FTPFile[] directories = f.listDirectories();
        FTPFile[] files = f.listFiles();
        for(FTPFile file:directories){
            if (!file.getName().equalsIgnoreCase("backup")) {
                backupDirectory=file;
            } else {
               f.makeDirectory("backup");
            }
        }
        for(FTPFile file: files){
            if(file.getName().equals(fileToBeUpload.getName())){
                //copy file to backupDirectory
            }
        }

    } catch (IOException e) {
        e.printStackTrace();
    }

}

---

编辑后的代码： 仍然存在问题，当我备份 zip 文件时，备份文件已损坏。

有没有人知道它的原因？

  public static void backupUploadWithCommonsFTP(File fileToBeUpload) {
    FTPClient f = new FTPClient();
    boolean backupDirectoryExist = false;
    boolean fileToBeUploadExist = false;
    FTPFile backupDirectory = null;
    try {
        f.connect(server.getServer());
        f.login(server.getUsername(), server.getPassword());
        FTPFile[] directories = f.listDirectories();
        // Check for existence of backup directory
        for (FTPFile file : directories) {
            String filename = file.getName();
            if (file.isDirectory() && filename.equalsIgnoreCase("backup")) {
                backupDirectory = file;
                backupDirectoryExist = true;
                break;
            }
        }
        if (!backupDirectoryExist) {
            f.makeDirectory("backup");
        }
        // Check if file already exist on the server
        f.changeWorkingDirectory("files");
        FTPFile[] files = f.listFiles();
        f.changeWorkingDirectory("backup");
        String filePathToBeBackup="/home/user/backup/";
        String prefix;
        String suffix;
        String fileNameToBeBackup;
        FTPFile fileReadyForBackup = null;
        f.setFileType(FTP.BINARY_FILE_TYPE);
        f.setFileTransferMode(FTP.BINARY_FILE_TYPE);
        for (FTPFile file : files) {
            if (file.isFile() && file.getName().equals(fileToBeUpload.getName())) {
                prefix = FilenameUtils.getBaseName(file.getName());
                suffix = ".".concat(FilenameUtils.getExtension(file.getName()));
                fileNameToBeBackup = prefix.concat(Calendar.getInstance().getTime().toString().concat(suffix));
                filePathToBeBackup = filePathToBeBackup.concat(fileNameToBeBackup);
                fileReadyForBackup = file;
                fileToBeUploadExist = true;
                break;
            }
        }
        // If file already exist on the server create a backup from it otherwise just upload the file.
        if(fileToBeUploadExist){
            ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
            f.retrieveFile(fileReadyForBackup.getName(), outputStream);
            InputStream is = new ByteArrayInputStream(outputStream.toByteArray());
            if(f.storeUniqueFile(filePathToBeBackup, is)){
                JOptionPane.showMessageDialog(null, "Backup succeeded.");
                f.changeWorkingDirectory("files");
                boolean reply = f.storeFile(fileToBeUpload.getName(), new FileInputStream(fileToBeUpload));
                if(reply){
                    JOptionPane.showMessageDialog(null,"Upload succeeded.");
                }else{
                    JOptionPane.showMessageDialog(null,"Upload failed after backup.");
                }
            }else{
                JOptionPane.showMessageDialog(null,"Backup failed.");
            }
        }else{
            f.changeWorkingDirectory("files");
            f.setFileType(FTP.BINARY_FILE_TYPE);
            f.enterLocalPassiveMode();
            InputStream inputStream = new FileInputStream(fileToBeUpload);
            ByteArrayInputStream in = new ByteArrayInputStream(FileUtils.readFileToByteArray(fileToBeUpload));
            boolean reply = f.storeFile(fileToBeUpload.getName(), in);
            System.out.println("Reply code for storing file to server: " + reply);
            if(!f.completePendingCommand()) {
                f.logout();
                f.disconnect();
                System.err.println("File transfer failed.");
                System.exit(1);
            }
            if(reply){

                JOptionPane.showMessageDialog(null,"File uploaded successfully without making backup." +
                        "\nReason: There wasn't any previous version of this file.");
            }else{
                JOptionPane.showMessageDialog(null,"Upload failed.");
            }
        }
        //Logout and disconnect from server
        in.close();
        f.logout();
        f.disconnect();
    } catch (IOException e) {
        e.printStackTrace();
    }

}

原文由 itro 发布，翻译遵循 CC BY-SA 4.0 许可协议

Answer 1

如果您使用的是 apache commons net FTPClient ，则有一种直接方法可以将文件从一个位置移动到另一个位置（如果 user 具有适当的权限）。

 ftpClient.rename(from, to);

或者，如果您熟悉 ftp commands ，您可以使用类似

ftpClient.sendCommand(FTPCommand.yourCommand, args);
if(FTPReply.isPositiveCompletion(ftpClient.getReplyCode())) {
     //command successful;
} else {
     //check for reply code, and take appropriate action.
}

如果您使用任何其他客户端，请阅读文档，客户端实现之间不会有太大变化。

更新：

以上方法将文件移动到 to 目录，即该文件将不再存在于 from 目录中。基本上 ftp 协议意味着从 local <-> remote 或 remote <-> other remote 传输文件，但不在服务器中传输。

此处的工作会更简单，将完整文件获取到本地 InputStream 并将其作为备份目录中的新文件写回服务器。

得到完整的文件，

 ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
ftpClient.retrieveFile(fileName, outputStream);
InputStream is = new ByteArrayInputStream(outputStream.toByteArray());

现在，将此流存储到备份目录。首先我们需要将工作目录更改为备份目录。

 // assuming backup directory is with in current working directory
ftpClient.setFileType(FTP.BINARY_FILE_TYPE);//binary files
ftpClient.changeWorkingDirectory("backup");
//this overwrites the existing file
ftpClient.storeFile(fileName, is);
//if you don't want to overwrite it use storeUniqueFile

希望这对你有帮助..

原文由 RP- 发布，翻译遵循 CC BY-SA 3.0 许可协议

Answer 2

试试这个方法，

我正在使用 apache 的库。

ftpClient.rename(from, to) 会更容易，我在下面的代码中提到了在哪里添加 ftpClient.rename(from,to)。

 public void goforIt(){

        FTPClient con = null;

        try
        {
            con = new FTPClient();
            con.connect("www.ujudgeit.net");

            if (con.login("ujud3", "Stevejobs27!!!!"))
            {
                con.enterLocalPassiveMode(); // important!
                con.setFileType(FTP.BINARY_FILE_TYPE);
                String data = "/sdcard/prerakm4a.m4a";
                ByteArrayInputStream(data.getBytes());
                FileInputStream in = new FileInputStream(new File(data));
                boolean result = con.storeFile("/Ads/prerakm4a.m4a", in);
                in.close();
                if (result)
                       {
                            Log.v("upload result", "succeeded");

//$$$$$$$$$$$$$$$$$$$$$$$$$$\(在此处添加备份\)$$$$$$$$$$$$$\( \)$$$$$$$$$$$$$$$$//

                    // Now here you can store the file into a backup location

                  // Use ftpClient.rename(from, to) to place it in backup

//$$$$$$$$$$$$$$$$$$$$$$$$$$\(在此处添加备份\)$$$$$$$$$$$$$\( \)$$$$$$$$$$$$$$$$//

                        }
                con.logout();
                con.disconnect();
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }

    }

原文由 Kumar Vivek Mitra 发布，翻译遵循 CC BY-SA 3.0 许可协议