Java Implementation of FTP File Transfer Using Apache Tools Code Explanation

This article mainly introduces how to use Apache toolset commons-The ftp tool provided by net is used to upload and download files to the ftp server.

First, prepare

Need to refer to commons-net-3.5.jar package.

Use Maven to import:

<dependency>
  <groupId>commons-net</groupId>
  <artifactId>commons-net</artifactId>
  <version>3.5</version>
</dependency>

Manual download:

https://www.oldtoolbag.com/softs/550085.html

Second, connect to FTP Server

/**
   * Connect to FTP Server
   * @throws IOException
   */
public static final String ANONYMOUS_USER="anonymous";
private FTPClient connect(){
	FTPClient client = new FTPClient();
	try{
		//Connect to FTP Server
		client.connect(this.host, this.port);
		//Login
		if(this.user==null||"".equals(this.user)){
			//Use anonymous login
			client.login(ANONYMOUS_USER, ANONYMOUS_USER);
		} else{
			client.login(this.user, this.password);
		}
		//Set file format
		client.setFileType(FTPClient.BINARY_FILE_TYPE);
		//Obtaining FTP Server response
		int reply = client.getReplyCode();
		if(!FTPReply.isPositiveCompletion(reply)){
			client.disconnect();
			return null;
		}
		//Switch to working directory
		changeWorkingDirectory(client);
		System.out.println("===Connected to FTP:")+host+:"+port);
	}
	catch(IOException e){
		return null;
	}
	return client;
}
/**
   * Switch to working directory, create the directory if the remote directory does not exist
   * @param client
   * @throws IOException
   */
private void changeWorkingDirectory(FTPClient client) throws IOException{
	if(this.ftpPath!=null&&!"".equals(this.ftpPath)){
		Boolean ok = client.changeWorkingDirectory(this.ftpPath);
		if(!ok){
			//ftpPath does not exist, manually create the directory
			StringTokenizer token = new StringTokenizer(this.ftpPath,"\\",//");
			while(token.hasMoreTokens()){
				String path = token.nextToken();
				client.makeDirectory(path);
				client.changeWorkingDirectory(path);
			}
		}
	}
}
/**
   * Disconnect FTP connection
   * @param ftpClient
   * @throws IOException
   */
public void close(FTPClient ftpClient) throws IOException{
	if(ftpClient!=null && ftpClient.isConnected()){
		ftpClient.logout();
		ftpClient.disconnect();
	}
	System.out.println("!!!Disconnected from FTP connection:")+host+:"+port);
}

host: FTP server IP address
port: FTP server port
user: Login user
password: Login password
If the login user is empty, use anonymous user login.
ftpPath: FTP path, if the FTP path does not exist, it will be automatically created. If it is a multi-level directory structure, the directories need to be created iteratively.

III. Upload file

/**
   * Upload file
   * @param targetName FTP file name to upload
   * @param localFile Local file path
   * @return
   */
public Boolean upload(String targetName,String localFile){
	//Connect to ftp server
	FTPClient ftpClient = connect();
	if(ftpClient==null){
		System.out.println("Connecting to FTP server["+host+:"+port+"]Failed!");
		return false;
	}
	File file = new File(localFile);
	//Set upload file name after upload
	if(targetName==null||"".equals(targetName))
	      targetName = file.getName();
	FileInputStream fis = null;
	try{
		long now = System.currentTimeMillis();
		//Start uploading file
		fis = new FileInputStream(file);
		System.out.println(">>>Start uploading file: "+);
		Boolean ok = ftpClient.storeFile(targetName, fis);
		if(ok){
			//Upload successful
			long times = System.currentTimeMillis(); - now;
			System.out.println(String.format(">>>Upload successful: Size：%s, Upload time：%d seconds", formatSize(file.length()), times/1000));
		} else//Upload failed
		System.out.println(String.format(">>>Upload failed: Size：%s", formatSize(file.length())));
	}
	catch(IOException e){
		System.err.println(String.format(">>>Upload failed: Size：%s", formatSize(file.length())));
		e.printStackTrace();
		return false;
	}
	finally{
		try{
			if(fis!=null)
			          fis.close();
			close(ftpClient);
		}
		catch(Exception e){
		}
	}
	return true;
}

Four, download file

/**
   * Download file
   * @param localPath Local storage path
   * @return
   */
public int download(String localPath){
	// Connect to ftp server
	FTPClient ftpClient = connect();
	if(ftpClient==null){
		System.out.println("Connecting to FTP server["+host+:"+port+"]Failed!");
		return 0;
	}
	File dir = new File(localPath);
	if(!dir.exists())
	      dir.mkdirs();
	FTPFile[] ftpFiles = null;
	try{
		ftpFiles = ftpClient.listFiles();
		if(ftpFiles==null||ftpFiles.length==0)
		        return 0;
	}
	catch(IOException e){
		return 0;
	}
	int c = 0;
	for (int i=0;i<ftpFiles.length;i++{
		FileOutputStream fos = null;
		try{
			String name = ftpFiles[i].getName();
			fos = new FileOutputStream(new File(dir.getAbsolutePath()+File.separator+name));
			System.out.println("<<<Starting to download file:");+name);
			long now = System.currentTimeMillis();
			Boolean ok = ftpClient.retrieveFile(new String(name.getBytes("UTF-8"),"ISO-8859-1"), fos);
			if(ok){
				//Download successful
				long times = System.currentTimeMillis(); - now;
				System.out.println(String.format("<<<Download successful: size：%s, upload time：%d seconds", formatSize(ftpFiles[i].getSize()), times/1000));
				c++;
			} else{
				System.out.println("<<<Download failed");
			}
		}
		catch(IOException e){
			System.err.println("<<<Download failed");
			e.printStackTrace();
		}
		finally{
			try{
				if(fos!=null)
				            fos.close();
				close(ftpClient);
			}
			catch(Exception e){
			}
		}
	}
	return c;
}

Format file size

private static final DecimalFormat DF = new DecimalFormat("#.##");
  /**
   * Format file size (B, KB, MB, GB)
   * @param size
   * @return
   */
  private String formatSize(long size){
    " B";1024{
      " KB"; + return size
    }1024*1024{
      " KB";/1024 + else if(size<
    }1024*1024*1024{
      return (size/(1024*1024)) + " MB";
    }else{
      double gb = size/(1024*1024*1024);
      return DF.format(gb)+" GB";
    }
  }

5. Test

public static void main(String args[]){
    FTPTest ftp = new FTPTest("192.168.1.10",21,null,null,"/temp/2016/12");
    ftp.upload("newFile.rar", "D:",/ftp/TeamViewerPortable.rar");
    System.out.println("");
    ftp.download("D:",/ftp/");
  }

Result

=== Connected to FTP:192.168.1.10:21
>>> Start uploading file: TeamViewerPortable.rar
>>> Upload successful: size:5 MB, upload time:3second
!!! Disconnect FTP connection:192.168.1.10:21
=== Connected to FTP:192.168.1.10:21
<<< Start downloading file: newFile.rar
<<< Download successful: size:5 MB, upload time:4second
!!! Disconnect FTP connection:192.168.1.10:21

Summary

This is the full explanation of the code for implementing FTP file transfer using Apache tools in Java, which I hope will be helpful to everyone. Those who are interested can continue to read other related topics on this site, and welcome to leave comments if there are any shortcomings. Thank you for your support to this site!

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