How to copy a file on the FTP server to a directory on the same server in Java?

Question

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

Answer 1

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);

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.
}

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

UPDATE:

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.

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.

to get the complete file,

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

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

Hope this helps you..