How to Check if a File Exists on an SFTP Server Using JSch in Java?

If you're working with JSch to interact with an SFTP server in Java, you might need to verify whether a file exists before performing operations like reading, downloading, or deleting it. The stat() method of ChannelSftp can be used for this purpose.

Implementation: The following method attempts to retrieve the file attributes using channelSftp.stat(remoteFilePath). If the file exists, the method returns true. If the file does not exist, it catches the SftpException and checks if the error code is SSH_FX_NO_SUCH_FILE, indicating that the file is missing.

  private boolean verifyFileExists(ChannelSftp channelSftp, String remoteFilePath) {
    try {
        // Attempt to get the file attributes
        channelSftp.stat(remoteFilePath);
        System.out.println("File exists on the remote server: " + remoteFilePath);
        return true;
    } catch (SftpException e) {
        if (e.id == ChannelSftp.SSH_FX_NO_SUCH_FILE) {
             System.out.println("File does not exist on the remote server: " + remoteFilePath);
        } else {
            System.out.println("Error checking file existence: " + e.getMessage());
        }
        return false;
    }
}

Explanation:

1. The method tries to retrieve the file metadata using stat(remoteFilePath).

2. If the file exists, stat() executes successfully, and we return true.

3. If an SftpException occurs:

   i)If an SftpException occurs: If the error code is SSH_FX_NO_SUCH_FILE, the file does not exist, and we return false.

   ii)For any other exception, an error message is printed, and false is returned.

Why Use stat() Instead of ls()?

While ls() can list files, it is inefficient for checking a single file's existence because it retrieves a list of files and requires additional processing. Using stat() is more efficient for this specific use case.