Websocket基本用法

1.Websocket介绍

WebSocket是基于TCP的一种新的网络协议。它实现了浏览器与服务器全双工通信——浏览器和服务器只需要完成一次握手，两者之间就可以创建持久性的连接，并进行双向数据传输。

应用场景：

视频弹幕
网页聊天
体育实况更新
股票基金报价实时更新

2.实现步骤

①直接使用websocket.html页面作为WebSocket客户端

<!DOCTYPE HTML>
<html>
<head><meta charset="UTF-8"><title>WebSocket Demo</title>
</head>
<body><input id="text" type="text" /><button onclick="send()">发送消息</button><button onclick="closeWebSocket()">关闭连接</button><div id="message"></div>
</body>
<script type="text/javascript">var websocket = null;var clientId = Math.random().toString(36).substr(2);//判断当前浏览器是否支持WebSocketif('WebSocket' in window){//连接WebSocket节点websocket = new WebSocket("ws://localhost:8080/ws/"+clientId);}else{alert('Not support websocket')}//连接发生错误的回调方法websocket.onerror = function(){setMessageInnerHTML("error");};//连接成功建立的回调方法websocket.onopen = function(){setMessageInnerHTML("连接成功");}//接收到消息的回调方法websocket.onmessage = function(event){setMessageInnerHTML(event.data);}//连接关闭的回调方法websocket.onclose = function(){setMessageInnerHTML("close");}//监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。window.onbeforeunload = function(){websocket.close();}//将消息显示在网页上function setMessageInnerHTML(innerHTML){document.getElementById('message').innerHTML += innerHTML + '<br/>';}//发送消息function send(){var message = document.getElementById('text').value;websocket.send(message);}//关闭连接function closeWebSocket() {websocket.close();}
</script>
</html>

②导入WebSocket的maven坐标

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-websocket</artifactId>
</dependency>

③导入WebSocket服务端组件WebSocketServer，用于和客户端通信

import org.springframework.stereotype.Component;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;/*** WebSocket服务*/
@Component
@ServerEndpoint("/ws/{sid}")
public class WebSocketServer {//存放会话对象private static Map<String, Session> sessionMap = new HashMap();/*** 连接建立成功调用的方法*/@OnOpenpublic void onOpen(Session session, @PathParam("sid") String sid) {System.out.println("客户端：" + sid + "建立连接");sessionMap.put(sid, session);}/*** 收到客户端消息后调用的方法** @param message 客户端发送过来的消息*/@OnMessagepublic void onMessage(String message, @PathParam("sid") String sid) {System.out.println("收到来自客户端：" + sid + "的信息:" + message);}/*** 连接关闭调用的方法** @param sid*/@OnClosepublic void onClose(@PathParam("sid") String sid) {System.out.println("连接断开:" + sid);sessionMap.remove(sid);}/*** 群发** @param message*/public void sendToAllClient(String message) {Collection<Session> sessions = sessionMap.values();for (Session session : sessions) {try {//服务器向客户端发送消息session.getBasicRemote().sendText(message);} catch (Exception e) {e.printStackTrace();}}}}

④导入配置类WebSocketConfiguration，注册WebSocket的服务端组件

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;/*** WebSocket配置类，用于注册WebSocket的Bean*/
@Configuration
public class WebSocketConfiguration {@Beanpublic ServerEndpointExporter serverEndpointExporter() {return new ServerEndpointExporter();}}

⑤导入定时任务类WebSocketTask，定时向客户端推送数据

import com.sky.websocket.WebSocketServer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;@Component
public class WebSocketTask {@Autowiredprivate WebSocketServer webSocketServer;/*** 通过WebSocket每隔5秒向客户端发送消息*/@Scheduled(cron = "0/5 * * * * ?")public void sendMessageToClient() {webSocketServer.sendToAllClient("这是来自服务端的消息：" + DateTimeFormatter.ofPattern("HH:mm:ss").format(LocalDateTime.now()));}
}