File Upload/Retrieve From Ftp With Jakarta Commons Net

Sometimes it is required to read and store files from Ftp file servers. For these operations Jakarta Commons Net library provides easy to implement functions.

In order to start working with Commons Net library add following lines into your Maven enabled project's pom.xml file.

 
   commons-net
   commons-net
   1.0.0
 

General procedure to start with ftp server is as follows:

1- connect to server
2- login with userName and Password
3- retrieve list of files from specified ftp folder
4- save the file from ftp to local
5- save the file from local to ftp
6- sometimes it is required to check for response codes from ftp
7- complete operations and disconnect

FtpConnect() method connects to remote ftp server, reads file content, save it to local director, then save a copy of it to another remote ftp location.

package apache.commons.net.ftpclient;

import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.apache.commons.net.ftp.FTPReply;

public class FtpClientService {
 
 public FtpClientService(){  
 }
 
 public static void FtpConnect(){
  String userName="ftpLoginUserName";
  String passWord = "ftppass";
  String ftpAddress = "ftp.somedomain.com";
  String retrieveFromFTPFolder = "RemoteFolderName/";
  String saveToLocalFolder = "/LocalFolder/";
  String saveToFtpFolder = "/ftpUploadFolder/";
  String strLine;
  DataInputStream inputStream = null;
  BufferedReader bufferedReader = null;
  FTPClient client = null;
  FTPFile[] ftpFiles = null;
  int reply;
 
  try{
   client = new FTPClient();
   client.connect(ftpAddress);
   client.login(userName, passWord);
   ftpFiles = client.listFiles(retrieveFromFTPFolder);  //retrieve list of files from ftp server
   if (ftpFiles != null && ftpFiles.length > 0) {
    for (FTPFile file : ftpFiles) {  // get specified file from folder
     if(file.isFile() && file.getName().equals("PrivateFile")){
      //read content of specific file from ftp
      inputStream = new DataInputStream(client.retrieveFileStream(retrieveFromFTPFolder+file.getName()));
      bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
      //save file from ftp to local directory
      File fileToWrite = new File(saveToLocalFolder+file.getName());
      DataOutputStream out = new DataOutputStream(new BufferedOutputStream(new FileOutputStream(fileToWrite)));
      while ((strLine = bufferedReader.readLine()) != null) {
       out.writeBytes(strLine);
          out.writeBytes("\n");
      }
      out.close();
      //check for reply code of ftp server if required then relogin
      reply = client.getReplyCode();
               if (!FTPReply.isPositiveCompletion(reply))
               {
                System.err.println("FTP server refused connection.");
                client.disconnect();
                client = new FTPClient();
                client.connect(ftpAddress);
                client.login(userName, passWord);                    
               }  
               //save file from local to remote ftp file server
      File fileToUpload = new File(saveToLocalFolder + file.getName());
      FileInputStream fileInputStream = new FileInputStream(fileToUpload);
      client.storeFile(saveToFtpFolder + file.getName(), fileInputStream); 
      break;
     }
    }
   }
  }
  catch (Exception e) {
   if (client.isConnected()) {
    try {
     client.logout();  
     client.disconnect();  
    } catch (IOException f) {
     // do nothing
    }
   }
  }
  finally{
   if (client.isConnected())
            {
                try
                {
                 client.logout();
                 client.disconnect();
                }
                catch (IOException f)
                {
                }
            }
  }  
 }
 
 public static void main(String[] args) {
  FtpConnect();
 }
}