In the article Java FTP list files and directories example, we described how to query all files and sub directories in a given directory. However, in some particular cases, we don’t need to list everything inside a directory. Instead, we just want to search for only the files and directories which meet some certain criteria, e.g. only files; only directories; only files that have .html extension; etc. To do so, we can use the following method of the FTPClientclass: 

FTPFile[] listFiles(String pathname, FTPFileFilter filter) 

In this method, the noticeable parameter is FTPFileFilter which is used to filter out the listing result. This interface declares a single method: 

boolean accept(FTPFile file) 

So to provide our own filter implementation, we have to create a class that implements the FTPFileFilter interface and its accept() method. For example:

FTPFileFilter filter = new FTPFileFilter() {

	@Override
	public boolean accept(FTPFile ftpFile) {

		return ftpFile.isFile();

	}
};

This filter implementation class will return only files (filter out directories) in the listing result. Then we can call the listFiles() method as follows:

FTPFile[] result = ftpClient.listFiles("Upload", filter);

Often, the more compact syntax is used:

FTPFile[] result = ftpClient.listFiles("Upload", new FTPFileFilter() {

	@Override
	public boolean accept(FTPFile ftpFile) {
		return ftpFile.isFile();
	}
});

Here are some other examples of implementing the FTPFileFilter interface:

• Search for only directories:
  

  FTPFileFilter filter = new FTPFileFilter() {
  
  	@Override
  	public boolean accept(FTPFile ftpFile) {
  
  		return ftpFile.isDirectory();
  
  	}
  };

   

• Search for only .html files:
  

  FTPFileFilter filter = new FTPFileFilter() {
  
  	@Override
  	public boolean accept(FTPFile ftpFile) {
  
  		return (ftpFile.isFile() && ftpFile.getName().endsWith(".html"));
  	}
  };

   

• Search for only files whose name contain the word “Java”:
  

  FTPFileFilter filter = new FTPFileFilter() {
  
  	@Override
  	public boolean accept(FTPFile ftpFile) {
  
  		return (ftpFile.isFile() && ftpFile.getName().contains("Java"));
  	}
  };

   

The following is a complete example program that connects to a FTP server then searches for only files containing the word “Java” in their names:

package net.codejava.ftp;

import java.io.IOException;

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

/**
 * This program demonstrates how to search for files and directories on a FTP
 * server using the Apache Commons Net API.
 * @author www.codejava.net
 *
 */
public class FTPSearchDemo {

	public static void main(String[] args) {
		String server = "www.myserver.com";
		int port = 21;
		String user = "username";
		String pass = "password";

		FTPClient ftpClient = new FTPClient();

		try {
			ftpClient.connect(server, port);

			ftpClient.login(user, pass);

			ftpClient.enterLocalPassiveMode();

			String dirToSearch = "HNS/Website/Articles";

			FTPFileFilter filter = new FTPFileFilter() {

				@Override
				public boolean accept(FTPFile ftpFile) {

					return (ftpFile.isFile() && ftpFile.getName().contains("Java"));
				}
			};

			FTPFile[] result = ftpClient.listFiles(dirToSearch, filter);

			if (result != null && result.length > 0) {
				System.out.println("SEARCH RESULT:");
				for (FTPFile aFile : result) {
					System.out.println(aFile.getName());
				}
			}

			ftpClient.logout();

			ftpClient.disconnect();

		} catch (IOException ex) {
			ex.printStackTrace();
		} finally {
			if (ftpClient.isConnected()) {
				try {
					ftpClient.disconnect();
				} catch (IOException ex) {
					ex.printStackTrace();
				}
			}
		}
	}
}

Sample output of the above program:

SEARCH RESULT:
Code_JavaCore_2013-07-28.rar
Code_JavaCore_2013-07-28.rar.md5
Code_JavaEE_2013-07-13.rar
Code_JavaEE_2013-07-13.rar.md5
Code_JavaSE_2013-07-13.rar
Code_JavaSE_2013-07-13.rar.md5
Code_JavaSE_2013-07-28.rar
Code_JavaSE_2013-07-28.rar.md5

 

NOTES: The listFiles() method does not search in sub directories, it only searches for files and directories underneath the given directory.

 

Related Java FTP Tutorials:

• Java FTP list files and directories example
• List files and directories recursively on a FTP server
• Creating nested directory structure on a FTP server
• Java FTP example - Calculate total sub directories, files and size of a directory
• Determine if a directory or file exists on FTP server
• Remove an empty directory on a FTP server
• Rename file or directory on FTP server

 

Other Java FTP Tutorials:

• Connect and login to a FTP server
• Java FTP create directory example
• Java FTP file download tutorial and example
• Java FTP file upload tutorial and example
• Java FTP delete file example
• How to upload a directory to a FTP server
• How to download a complete folder from a FTP server