说明

如标题，举例需求场景：
前端与后端websocket连接上后，多用户登录，后端根据不同用户定时发消息给前端用于展示

代码实现

1、

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

2、

import org.springframework.context.annotation.Bean;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;@Component
public class WebSocketConfig {@Beanpublic ServerEndpointExporter serverEndpointExporter(){return new ServerEndpointExporter();}}

3、

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;import javax.websocket.OnClose;
import javax.websocket.OnError;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;
import java.util.Enumeration;
import java.util.LinkedList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArraySet;// 交给IOC容器
@Component
// 如果去掉/{userId} 那就是不分用户 给连接上的用户统一发送消息
@ServerEndpoint("/websocket/{userId}")
@Slf4j
public class WebSocketService {// 这里用ConcurrentHashMap 因为他是一个线程安全的Mapprivate static ConcurrentHashMap<String, CopyOnWriteArraySet<WebSocketService>> userwebSocketMap = new ConcurrentHashMap<>();private static ConcurrentHashMap<String, Integer> count = new ConcurrentHashMap<>();private String userId;/** 与某个客户端的连接会话，需要通过它来给客户端发送数据*/private Session session;/*** 连接建立成功调用的方法** @param session 可选的参数。session为与某个客户端的连接会话，需要通过它来给客户端发送数据*/@OnOpenpublic void onOpen(Session session, @PathParam("userId") final String userId) {this.session = session;this.userId = userId;System.out.println("session:" + session);System.out.println("userId:" + userId);if (!exitUser(userId)) {initUserInfo(userId);} else {CopyOnWriteArraySet<WebSocketService> webSocketServiceSet = getUserSocketSet(userId);webSocketServiceSet.add(this);userCountIncrease(userId);}System.out.println("有" + userId + "新连接加入！当前在线人数为" + getCurrUserCount(userId));}/*** 连接关闭调用的方法*/@OnClosepublic void onClose() {CopyOnWriteArraySet<WebSocketService> webSocketServiceSet = userwebSocketMap.get(userId);//从set中删除webSocketServiceSet.remove(this);//在线数减1userCountDecrement(userId);System.out.println("有一连接关闭！当前在线人数为" + getCurrUserCount(userId));}/*** 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* @param session 可选的参数*/@OnMessagepublic void onMessage(String message, Session session) {CopyOnWriteArraySet<WebSocketService> webSocketSet = userwebSocketMap.get(userId);System.out.println("来自客户端" + userId + "的消息:" + message);//群发消息for (WebSocketService item : webSocketSet) {try {item.sendMessage(message);} catch (IOException e) {e.printStackTrace();continue;}}}/*** 发生错误时调用** @param session* @param error*/@OnErrorpublic void onError(Session session, Throwable error) {System.out.println("发生错误");error.printStackTrace();}/*** 这个方法与上面几个方法不一样。没有用注解，是根据自己需要添加的方法。** @param message* @throws IOException*/public void sendMessage(String message) throws IOException {System.out.println("服务端推送" + userId + "的消息:" + message);this.session.getAsyncRemote().sendText(message);}/*** 这个方法与上面几个方法不一样。没有用注解，是根据自己需要添加的方法。   我是在有代办消息时 调用此接口 向指定用户发送消息** @param message* @throws IOException*/public void sendMessage(String userId, String message) throws IOException {System.out.println("服务端推送" + userId + "的消息:" + message);CopyOnWriteArraySet<WebSocketService> webSocketSet = userwebSocketMap.get(userId);//群发消息for (WebSocketService item : webSocketSet) {try {item.session.getBasicRemote().sendText(message);} catch (IOException e) {e.printStackTrace();continue;}}}public void sendOpenAllUserMessage(List<String> userIds, String message) {for (String userId : userIds) {CopyOnWriteArraySet<WebSocketService> webSocketSet = userwebSocketMap.get(userId);//群发消息for (WebSocketService item : webSocketSet) {try {item.session.getBasicRemote().sendText(message);} catch (IOException e) {e.printStackTrace();continue;}}}}public boolean exitUser(String userId) {return userwebSocketMap.containsKey(userId);}public CopyOnWriteArraySet<WebSocketService> getUserSocketSet(String userId) {return userwebSocketMap.get(userId);}public void userCountIncrease(String userId) {if (count.containsKey(userId)) {count.put(userId, count.get(userId) + 1);}}public void userCountDecrement(String userId) {if (count.containsKey(userId)) {count.put(userId, count.get(userId) - 1);}}public void removeUserConunt(String userId) {count.remove(userId);}public Integer getCurrUserCount(String userId) {return count.get(userId);}private void initUserInfo(String userId) {CopyOnWriteArraySet<WebSocketService> webSocketServiceSet = new CopyOnWriteArraySet<WebSocketService>();webSocketServiceSet.add(this);userwebSocketMap.put(userId, webSocketServiceSet);count.put(userId, 1);}public List<String> getAllUser() {List<String> allUser = new LinkedList<>();Enumeration<String> keys = userwebSocketMap.keys();while (keys.hasMoreElements()) {String key = keys.nextElement();allUser.add(key);}return allUser;}}

4、

import com.lq.demo1.service.WebSocketService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;import java.util.List;@EnableScheduling
@Configuration
@Slf4j
public class TaskTimer {@Autowiredprivate WebSocketService webSocketService;@Scheduled(cron = "0/10 * * * * ?")public void cleanToken() {//10s推送一次List<String> allUser = webSocketService.getAllUser();//自己可以定义不同用户发送的信息，这里不做演示了webSocketService.sendOpenAllUserMessage(allUser, "告警！");}}

@EnableScheduling

然后把项目启动，打开在线调试websocket连接

路径格式为：ws://localhost:8081/websocket/1

成功展示，也可以搞多个窗口，发送内容一致

$就先说到这$
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