is it possible to read the content of the file present in the ftp server? [duplicate] - spring-boot

Question

This is re-worded from a previous question (which was probably a bit unclear).
I want to download a text file via FTP from a remote server, read the contents of the text file into a string and then discard the file. I don't need to actually save the file.
I am using the Apache Commons library so I have:
import org.apache.commons.net.ftp.FTPClient;
Can anyone help please, without simply redirecting me to a page with lots of possible answers on?

Answer 1

Not going to do the work for you, but once you have your connection established, you can call retrieveFile and pass it an OutputStream. You can google around and find the rest...
FTPClient ftp = new FTPClient();
...
ByteArrayOutputStream myVar = new ByteArrayOutputStream();
ftp.retrieveFile("remoteFileName.txt", myVar);
ByteArrayOutputStream
retrieveFile

Answer 2

Normally I'd leave a comment asking 'What have you tried?'. But now I'm feeling more generous :-)
Here you go:
private void ftpDownload() {
FTPClient ftp = null;
try {
ftp = new FTPClient();
ftp.connect(mServer);
try {
int reply = ftp.getReplyCode();
if (!FTPReply.isPositiveCompletion(reply)) {
throw new Exception("Connect failed: " + ftp.getReplyString());
}
if (!ftp.login(mUser, mPassword)) {
throw new Exception("Login failed: " + ftp.getReplyString());
}
try {
ftp.enterLocalPassiveMode();
if (!ftp.setFileType(FTP.BINARY_FILE_TYPE)) {
Log.e(TAG, "Setting binary file type failed.");
}
transferFile(ftp);
} catch(Exception e) {
handleThrowable(e);
} finally {
if (!ftp.logout()) {
Log.e(TAG, "Logout failed.");
}
}
} catch(Exception e) {
handleThrowable(e);
} finally {
ftp.disconnect();
}
} catch(Exception e) {
handleThrowable(e);
}
}
private void transferFile(FTPClient ftp) throws Exception {
long fileSize = getFileSize(ftp, mFilePath);
InputStream is = retrieveFileStream(ftp, mFilePath);
downloadFile(is, buffer, fileSize);
is.close();
if (!ftp.completePendingCommand()) {
throw new Exception("Pending command failed: " + ftp.getReplyString());
}
}
private InputStream retrieveFileStream(FTPClient ftp, String filePath)
throws Exception {
InputStream is = ftp.retrieveFileStream(filePath);
int reply = ftp.getReplyCode();
if (is == null
|| (!FTPReply.isPositivePreliminary(reply)
&& !FTPReply.isPositiveCompletion(reply))) {
throw new Exception(ftp.getReplyString());
}
return is;
}
private byte[] downloadFile(InputStream is, long fileSize)
throws Exception {
byte[] buffer = new byte[fileSize];
if (is.read(buffer, 0, buffer.length)) == -1) {
return null;
}
return buffer; // <-- Here is your file's contents !!!
}
private long getFileSize(FTPClient ftp, String filePath) throws Exception {
long fileSize = 0;
FTPFile[] files = ftp.listFiles(filePath);
if (files.length == 1 && files[0].isFile()) {
fileSize = files[0].getSize();
}
Log.i(TAG, "File size = " + fileSize);
return fileSize;
}

Answer 3

You can just skip the download to local filesystem part and do:
FTPClient ftpClient = new FTPClient();
try {
ftpClient.connect(server, port);
ftpClient.login(user, pass);
ftpClient.enterLocalPassiveMode();
ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
InputStream inputStream = ftpClient.retrieveFileStream("/folder/file.dat");
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "Cp1252"));
while(reader.ready()) {
System.out.println(reader.readLine()); // Or whatever
}
inputStream.close();
} catch (IOException ex) {
ex.printStackTrace();
} finally {
try {
if (ftpClient.isConnected()) {
ftpClient.logout();
ftpClient.disconnect();
}
} catch (IOException ex) {
ex.printStackTrace();
}
}