在Java中实现用户之间的通讯可以通过多种方式，这里我将介绍两种常见的方法：使用Socket编程和使用WebSocket。
1. 使用Socket编程
Socket编程是实现网络通讯的基础，它允许两个设备之间进行数据交换。以下是一个简单的Java Socket编程示例，用于实现客户端和服务器之间的基本通讯。
服务器端代码（Server.java）
import java.io.*;
import java.net.*;public class Server {public static void main(String[] args) throws IOException {ServerSocket serverSocket = new ServerSocket(1234); // 服务器监听的端口号System.out.println("Server is listening on port 1234");while (true) {Socket socket = serverSocket.accept(); // 接受客户端连接new ServerThread(socket).start(); // 为每个连接创建一个新线程}}
}class ServerThread extends Thread {private Socket socket;public ServerThread(Socket socket) {this.socket = socket;}public void run() {try {BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));OutputStream out = socket.getOutputStream();PrintWriter writer = new PrintWriter(out, true);String inputLine;while ((inputLine = in.readLine()) != null) {System.out.println("Server received: " + inputLine);writer.println("Echo: " + inputLine);}} catch (IOException e) {e.printStackTrace();} finally {try {socket.close();} catch (IOException e) {e.printStackTrace();}}}
}客户端代码（Client.java）
import java.io.*;
import java.net.*;public class Client {public static void main(String[] args) throws IOException {Socket socket = new Socket("localhost", 1234); // 连接到服务器BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));PrintWriter out = new PrintWriter(socket.getOutputStream(), true);BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));new Thread(() -> {try {String serverResponse;while ((serverResponse = in.readLine()) != null) {System.out.println("Server says: " + serverResponse);}} catch (IOException e) {e.printStackTrace();}}).start();String userInput;System.out.println("Enter messages (leave empty line to quit):");while ((userInput = stdIn.readLine()) != null) {out.println(userInput);if (userInput.trim().isEmpty()) {break;}}socket.close();System.exit(0);}
}2. 使用WebSocket
WebSocket提供了全双工通讯，允许服务器主动发送信息给客户端。这通常用于需要实时通讯的应用，如聊天应用。
服务器端代码（使用Spring Boot）
首先，你需要添加Spring Boot的依赖到你的pom.xml文件中：
然后，创建WebSocket配置：
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {@Overridepublic void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {registry.addHandler(new ChatHandler(), "/chat").setAllowedOrigins("*");}
}创建WebSocket处理器：
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler;public class ChatHandler extends TextWebSocketHandler {@Overridepublic void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {for (WebSocketSession s : sessions) {s.sendMessage(new TextMessage("Echo: " + message.getPayload()));}}
}客户端代码（HTML + JavaScript）
<!DOCTYPE html>
<html>
<head><title>WebSocket Test</title><script>var ws = new WebSocket("ws://localhost:8080/chat");ws.onmessage = function(event) {var message = event.data;console.log(message);document.getElementById('messages').innerHTML += '<li>' + message + '</li>';};function sendMessage() {var input = document.getElementById('messageInput');ws.send(input.value);input.value = '';}</script>
</head>
<body><ul id="messages"></ul><input type="text" id="messageInput"/><button onclick="sendMessage()">Send</button>
</body>
</html>这两种方法都可以实现用户之间的通讯，选择哪种取决于你的具体需求和应用场景。
