注意事項：

1. 匯入jar包：commons-net-3.6.jar（百度雲分享）
2. 用於登陸FTP伺服器的賬戶對檔案操作目錄必須有讀寫許可權

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.junit.Test;
 

上傳檔案

說明：將本地 D:/test/ 目錄下的 uploadfile.txt 檔案上傳到伺服器 /home/ftp/log 目錄下，檔名為 log_20180913

	public void uploadFile() {
                
		String ip = "xxx.xxx.xxx.xxx";            //伺服器IP地址	
		String userName = "yourUserName";        //用於登陸伺服器的使用者名稱				
		String passWord = "yourPassord";            //登陸密碼
		String remoteDirectoryPath = "/home/ftp/log";    //遠端資料夾的絕對路徑   	
		String localFilePath = "D:/test/uploadfile.txt";    //要上傳到伺服器的本地檔案的絕對路徑
		String remoteFileName = "log_20180913";    //將本地檔案上傳到伺服器後文件的名字			
		
		FTPClient ftpClient = new FTPClient();
		try {
			ftpClient.connect(ip);
			boolean isLogin = ftpClient.login(userName, passWord);
			System.out.println("uploadFile 登陸成功？ " + isLogin);
			ftpClient.changeWorkingDirectory(remoteDirectoryPath);
			InputStream is = new FileInputStream(new File(localFilePath));
			boolean isStore = ftpClient.storeFile(remoteFileName, is);
			System.out.println("上傳成功？ " + isStore);
		} catch (IOException e) {
			e.printStackTrace();
		}finally {
			try {
				ftpClient.logout();
				ftpClient.disconnect();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
 

下載檔案

說明：將伺服器 /home/ftp/log 路徑下的 log_20180913 檔案下載到本地 D:/test 目錄下，檔名為java.txt

public void downloadFile() {
		String ip = "xxx.xxx.xxx.xxx"; // 伺服器IP地址
		String username = "yourUsername"; // 用於登陸伺服器的使用者名稱
		String password = "yourPassword"; // 登陸密碼
		String remoteDirectoryPath = "/home/ftp/log"; // 遠端資料夾的絕對路徑
		String localFilePath = "D:/test/java.txt"; // 要上傳到伺服器的本地檔案的絕對路徑
		String remoteFileName = "log_20180913"; // 將本地檔案上傳到伺服器後文件的名字

		FTPClient ftpClient = new FTPClient();
		try {
			ftpClient.connect(ip);
			boolean isLogin = ftpClient.login(username, password);
			System.out.println("登陸成功？ " + isLogin);
			ftpClient.changeWorkingDirectory(remoteDirectoryPath);
			FTPFile[] files = ftpClient.listFiles();
			for (FTPFile file : files) {
				if (file.getName().equals(remoteFileName)) {
					OutputStream os = new FileOutputStream(new File(localFilePath));
					ftpClient.retrieveFile(file.getName(), os);
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				ftpClient.logout();
				ftpClient.disconnect();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
 

向檔案追加內容

說明：向伺服器 /home/ftp/log 路徑下的 log_20180913 檔案追加內容：\nhello append content

public void appendFile() {
		String ip = "xxx.xxx.xxx.xxx"; // 伺服器IP地址
		String username = "yourUsername"; // 用於登陸伺服器的使用者名稱
		String password = "yourPassword"; // 登陸密碼
		String remoteDirectoryPath = "/home/ftp/log"; // 遠端資料夾的絕對路徑
		String remoteFileName = "log_20180913"; // 將本地檔案上傳到伺服器後文件的名字

		FTPClient ftpClient = new FTPClient();
		try {
			ftpClient.connect(ip);
			boolean isLogin = ftpClient.login(username, password);
			System.out.println("登陸成功？ " + isLogin);
			ftpClient.changeWorkingDirectory(remoteDirectoryPath);
			FTPFile[] ftpFiles = ftpClient.listFiles();
			for (FTPFile file : ftpFiles) {
				if (file.getName().equals(remoteFileName)) {
					ftpClient.setRestartOffset(file.getSize());
					OutputStream os = ftpClient.appendFileStream(remoteFileName);
					os.write("\nhello append content".getBytes("utf-8"));
					os.flush();
					os.close();
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				ftpClient.logout();
				ftpClient.disconnect();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

貼上GitHub原始檔：

https://github.com/tanmujin/FTPClient