websocet后台主动推送vue前台消息

需要的jar包依赖

        <!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-websocket -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
            <version>2.0.4.RELEASE</version>
        </dependency>

java部分WebSocket服务接口

import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
import javax.websocket.*;
import javax.websocket.server.PathParam;
import javax.websocket.server.ServerEndpoint;

import com.alibaba.fastjson.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;

/**
 * WebSocket服务接口
 *
 * @author wzw
 * @date 2022/08/23
 */
@ServerEndpoint(value = "/websocket/{userId}")
@Component
public class WebSocketServer {
    private final static Logger log = LoggerFactory.getLogger(WebSocketServer.class);

    /**
     * 存储登录用户的 sid 以及 session
     */
    private static ConcurrentHashMap<String, Session> connections = new ConcurrentHashMap<>(32);

    /**
     * 是WebSocket的Session
     */
    private Session session;

    /**
     * 统计在线人数
     */
    private static AtomicInteger onlineCount = new AtomicInteger();

    /**
     *  事件 --登录的人当你登录之后建立连接，此方法便会执行
     * @p