Java: Accessing a File from an FTP Server

问题:

So I have this FTP server with a bunch of folders and files inside.

My program needs to access this server, read all of the files, and display their data.

For development purposes I've been working with the files on my hard drive, right in the "src" folder.

But now that the server is up and running, I need to connect the software to it.

Basically what I want to do is get a list of the Files in a particular folder on the server.

This is what I have so far:

URL url = null;
File folder = null;
try {
    url = new URL ("ftp://username:[e-mail]/server");
    folder = new File (url.toURI());
} catch (Exception e) {
    e.printStackTrace();
}
data = Arrays.asList(folder.listFiles(new FileFilter () {
    public boolean accept(File file) {
        return file.isDirectory();
    }
}));

But I get the error "URI scheme is not 'file'."

I understand this is because my URL starts with "ftp://" and not "file:"

However I can't seem to figure out what I'm supposed to do about it!

Maybe there's a better way to go about this?

回答1:

File objects cannot handle an FTP connection, you need to use a URLConnection:

URL url = new URL ("ftp://username:[e-mail]/server");
URLConnection urlc = url.openConnection();
InputStream is = urlc.getInputStream();
...

Consider as an alternative FTPClient from Apache Commons Net which has support for many protocols. Here is an FTP list files example.

回答2:

if you use URI with file you can use your code but , but when you want to use ftp so you need to this kind of code; code list the name of the files under your ftp server

import java.net.*;
import java.io.*;

public class URLConnectionReader {
    public static void main(String[] args) throws Exception {
        URL url = new URL("ftp://username:[e-mail]/server");
        URLConnection con = url.openConnection();
        BufferedReader in = new BufferedReader(new InputStreamReader(
                                    con.getInputStream()));
        String inputLine;
        while ((inputLine = in.readLine()) != null) 
            System.out.println(inputLine);
        in.close();
    }
}

EDITED Demo Code Belongs to Codejava

package net.codejava.ftp;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;

public class FtpUrlListing {

    public static void main(String[] args) {
        String ftpUrl = "ftp://%s:%s@%s/%s;type=d";
        String host = "www.myserver.com";
        String user = "tom";
        String pass = "secret";
        String dirPath = "/projects/java";

        ftpUrl = String.format(ftpUrl, user, pass, host, dirPath);
        System.out.println("URL: " + ftpUrl);

        try {
            URL url = new URL(ftpUrl);
            URLConnection conn = url.openConnection();
            InputStream inputStream = conn.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

            String line = null;
            System.out.println("--- START ---");
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
            System.out.println("--- END ---");

            inputStream.close();
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}