问题描述

我正在使用 Apache Commons FTP 上传文件.在上传之前，我想检查该文件是否已存在于服务器上，并将其备份到同一服务器上的备份目录中.

I'm using Apache Commons FTP to upload a file. Before uploading I want to check if the file already exists on the server and make a backup from it to a backup directory on the same server.

有人知道如何将文件从 FTP 服务器复制到同一服务器上的备份目录吗?

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();
    }

}

<小时>

编辑代码:还是有问题，当我备份 zip 文件时，备份的文件已损坏.

Edited code: still there is a problem, when i backup zip file, the backup-ed file is corrupted.

有人知道原因吗?

 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." +
                        "
Reason: 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();
    }

}

推荐答案

如果你使用的是 apache commons net FTPClient，有一个直接的方法可以将文件从一个位置移动到另一个位置(如果user 有适当的权限).

If you are using apache commons net FTPClient, there is a direct method to move a file from one location to another location (if the user has proper permissions).

ftpClient.rename(from, to);

或者，如果你熟悉 ftp 命令，你可以使用类似

or, If you are familiar with ftp commands, you can use something like

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.

If you are using any other client, go through the documentation, There wont be much changes between client implementations.

更新:

上述方法将文件移动到 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 <-> 传输文件.远程或远程<->其他远程，但不能在服务器中传输.

Above approach moves the file to to directory, i.e, the file won't be there in from directory anymore. Basically ftp protocol meant to be transfer the files from local <-> remote or remote <-> other remote but not to transfer with in the server.

这里的工作会更简单，将完整的文件获取到本地 InputStream 并将其作为备份目录中的新文件写回服务器.

The work around here, would be simpler, get the complete file to a local InputStream and write it back to the server as a new file in the back up directory.

要获取完整的文件，

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.

now, store this stream to backup directory. First we need to change working directory to backup directory.

// 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

希望对你有所帮助..

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