Reading content from an ftp file

[igorland]

Hello. I am trying to read a content of file downloaded from ftp and return it as a String. This is what I use:

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;

import org.apache.commons.net.ftp.FTPClient;


public class Test {


	public static void main(String [] args) throws IOException	{
		FTPClient ftp = new FTPClient();
		ftp.connect("ftp://tgftp.nws.noaa.gov/data/observations/metar/stations/");
		InputStream in = ftp.retrieveFileStream("KLAS.TXT");
		
		BufferedInputStream inbf = new BufferedInputStream(in);
		
	    int bytesRead;
		byte[] buffer=new byte[1024]; 
		String fileContent=null;
		
		while((bytesRead=inbf.read(buffer))!=-1)
		   {
		       fileContent=new String(buffer,0,bytesRead); 
		   }
		   
		   System.out.println("File: " + fileContent);
		}
}

The code does not work, although all the links are correct. Thanks a lot for your help!

[Fubarable]

For one thing, you're over-writing the content of the fileContent String with each iteration of the loop. For another, if the data is truly String data, consider wrapping your InputStream in a InputStreamReader and that in a BufferedReader which should make getting text data much easier and more intuitive and less error prone.

[igorland]

Fubarable. Thank you very much! I changed the code based on your suggestion:

public static void main(String [] args) throws IOException	{
	       FTPClient ftp = new FTPClient();
	       InputStream in = ftp.retrieveFileStream("ftp://tgftp.nws.noaa.gov/data/observations/metar/stations/KLAX.TXT");
	       InputStreamReader isr = new InputStreamReader(in);
	       BufferedReader br = new BufferedReader(isr);
	       
	       int bytesRead = 0;        
	       byte[] buffer=new byte[1024];         
	       String fileContent=null;
	       
	       fileContent=new String(buffer,0,bytesRead);
	       
	       System.out.println(fileContent);
	}
}

No, it is not working either:

Exception in thread "main" java.lang.NullPointerException
	at org.apache.commons.net.SocketClient.getRemoteAddress(SocketClient.java:651)
	at org.apache.commons.net.ftp.FTPClient._openDataConnection_(FTPClient.java:732)
	at org.apache.commons.net.ftp.FTPClient._retrieveFileStream(FTPClient.java:1853)
	at org.apache.commons.net.ftp.FTPClient.retrieveFileStream(FTPClient.java:1844)
	at Test.main(Test.java:16)

When I open the file in IE, the file opens just fine, so the link is good. No idea what I am doing wrong! Thanks!

[Fubarable]

If you create a BufferedReader, consider using that object to read in your data rather than simply ignoring it. As to your NPE, what is happening on line 16 of Test.java?

[igorland]

Thanks. New version:

public static void main(String [] args) throws IOException	{
	       FTPClient ftp = new FTPClient();
	       InputStream in = ftp.retrieveFileStream("ftp://tgftp.nws.noaa.gov/data/observations/metar/stations/KLAX.TXT");
	       InputStreamReader isr = new InputStreamReader(in);
	       BufferedReader br = new BufferedReader(isr);
	       
	   
	       String fileContent= br.readLine();
	       
	       System.out.println(fileContent);

Line 16 is pointing to the InputStream line (with the ftp address). I wonder if I am connecting to the ftp correctly...

[igorland]

This worked!!!!!!!

public class Test1 {

	public final static String server = "ftp://tgftp.nws.noaa.gov/data/observations/metar/stations";
	public final static String fileName = "UAAA.TXT";
	
	
	public static void main(String[] args) {

		   System.out.println("Connecting to FTP server...");

		    // Connection String
		    URL url;
	
		    try {
		    	url = new URL(server + "/" + fileName);

		        URLConnection con = url.openConnection();
		        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));

		        System.out.println("Reading file start.");

		        String inputLine;
		        while ((inputLine = in.readLine()) != null)
		            System.out.println(inputLine);
		        in.close();
		        }
		        catch (FileNotFoundException e) {
		            System.out.println("File not find on server.");
		            System.exit(0);
		        }catch (Exception e) {
		            e.printStackTrace();
		        }
		        System.out.println("Read File Complete.");

		}

}

Thanks for your support!

[Fubarable]

I would declare the BufferedReader before the try block setting it initially to null, and would close the BufferedReader in a finally block after checking first that it's not null. Otherwise it looks good.

[igorland]

I did it. Great. Thank you so much!

[Fubarable]

Great and you're welcome!