公司领导提出了一个新的需求，那就是部门主管在有审批消息的情况下，需要看到提示消息。其实这种需求最简单的方法使接入短信、邮件、公众号平台。直接推送消息。但是，由于使自研项目，公司领导不想花钱，只能另辟蹊径。
WebSocket简介
WebSocket协议是基于TCP的一种新的网络协议。它实现了浏览器与服务器全双工（full-duplex）通信，即允许服务器主动发送信息给客户端。因此，在WebSocket中，浏览器和服务器只需要完成一次握手，两者之间就直接可以创建持久性的连接，并进行双向数据传输，客户端和服务器之间的数据交换变得更加简单。
WebSocket-实现后端推送消息给前端
依赖导入
<dependency> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-starter-websocketartifactId> <version>2.7.0version>dependency>代码实现
WebSocketConfig
import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.web.socket.server.standard.ServerEndpointExporter;@Configurationpublic class WebSocketConfig { @Bean public ServerEndpointExporter serverEndpointExporter() { return new ServerEndpointExporter(); }}WebSocketMessage–封装的消息结果类(非必须)
import lombok.Data;@Datapublic class NoticeWebsocketResp<T> { private String noticeType; private T noticeInfo;}WebSocketServer
import com.alibaba.fastjson.JSONObject;import com.mydemo.websocketdemo.domain.NoticeWebsocketResp;import lombok.extern.slf4j.Slf4j;import org.springframework.stereotype.Component;import org.springframework.util.StringUtils;import javax.websocket.*;import javax.websocket.server.PathParam;import javax.websocket.server.ServerEndpoint;import java.io.IOException;import java.util.*;import java.util.concurrent.ConcurrentHashMap;@ServerEndpoint("/notice/{userId}")@Component@Slf4jpublic class NoticeWebsocket { //记录连接的客户端 public static Map<String, Session> clients = new ConcurrentHashMap<>(); public static Map<String, Set<String>> conns = new ConcurrentHashMap<>(); private String sid = null; private String userId; @OnOpen public void onOpen(Session session, @PathParam("userId") String userId) { this.sid = UUID.randomUUID().toString(); this.userId = userId; clients.put(this.sid, session); Set<String> clientSet = conns.get(userId); if (clientSet==null){ clientSet = new HashSet<>(); conns.put(userId,clientSet); } clientSet.add(this.sid); log.info(this.sid + "连接开启！"); } @OnClose public void onClose() { log.info(this.sid + "连接断开！"); clients.remove(this.sid); } public static boolean isServerClose() { if (NoticeWebsocket.clients.values().size() == 0) { log.info("已断开"); return true; }else { log.info("已连接"); return false; } } public static void sendMessage(String noticeType){ NoticeWebsocketResp noticeWebsocketResp = new NoticeWebsocketResp(); noticeWebsocketResp.setNoticeType(noticeType); sendMessage(noticeWebsocketResp); } public static void sendMessage(NoticeWebsocketResp noticeWebsocketResp){ String message = JSONObject.toJSONString(noticeWebsocketResp); for (Session session1 : NoticeWebsocket.clients.values()) { try { session1.getBasicRemote().sendText(message); } catch (IOException e) { e.printStackTrace(); } } } public static void sendMessageByUserId(String userId, NoticeWebsocketResp noticeWebsocketResp) { if (!StringUtils.isEmpty(userId)) { String message = JSONObject.toJSONString(noticeWebsocketResp); Set<String> clientSet = conns.get(userId); if (clientSet != null) { Iterator<String> iterator = clientSet.iterator(); while (iterator.hasNext()) { String sid = iterator.next(); Session session = clients.get(sid); if (session != null) { try {session.getBasicRemote().sendText(message); } catch (IOException e) {e.printStackTrace(); } } } } } } @OnMessage public void onMessage(String message, Session session) { log.info("收到来自窗口"+this.userId+"的信息:"+message); } @OnError public void onError(Throwable error) { error.printStackTrace(); }}这样我们就配置好了websocket
测试准备
访问接口–当请求该接口时,主动推送消息
import com.mydemo.websocketdemo.domain.NoticeWebsocketResp;import com.mydemo.websocketdemo.websocketserver.NoticeWebsocket;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;@RestController@RequestMapping("/order")public class OrderController { @GetMapping("/test") public String test() { NoticeWebsocket.sendMessage("你好，WebSocket"); return "ok"; } @GetMapping("/test1") public String test1() { NoticeWebsocketResp noticeWebsocketResp = new NoticeWebsocketResp(); noticeWebsocketResp.setNoticeInfo("米奇妙妙屋"); NoticeWebsocket.sendMessageByUserId("1", noticeWebsocketResp); return "ok"; }}springboot启动类
import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class WebSocketApplication { public static void main(String[] args) { SpringApplication.run(WebSocketApplication.class,args); }}前端测试页面
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>SseEmitter</title></head><body><div id="message"></div></body><script>var limitConnect = 0;init();function init() {// 8080未默认端口,可自行替换 var ws = new WebSocket('ws://localhost:8080/notice/2');// 获取连接状态console.log('ws连接状态：' + ws.readyState);//监听是否连接成功ws.onopen = function () { console.log('ws连接状态：' + ws.readyState); limitConnect = 0; //连接成功则发送一个数据 ws.send('我们建立连接啦');}// 接听服务器发回的信息并处理展示ws.onmessage = function (data) { console.log('接收到来自服务器的消息：'); console.log(data); //完成通信后关闭WebSocket连接 // ws.close();}// 监听连接关闭事件ws.onclose = function () { // 监听整个过程中websocket的状态 console.log('ws连接状态：' + ws.readyState);reconnect();}// 监听并处理error事件ws.onerror = function (error) { console.log(error);}}function reconnect() { limitConnect ++; console.log("重连第" + limitConnect + "次"); setTimeout(function(){ init(); },2000); }</script></html>之后用浏览器打开html页面,显示如下:
连接成功
调用接口
localhost:8080/order/test
证明后端推送消息给前端成功
来源地址：https://blog.csdn.net/qq_45770147/article/details/130011485
