Java FTP example - Search for files and directories

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

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.

Attachments:

FTPSearchDemo.java

[Demo program]

1 kB