springboot整合websocket

1、添加依赖

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


        <dependency>
            <!-- fastjson -->
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>

2、添加配置文件

package com.cosmo.sandtable.configure;

import com.cosmo.sandtable.service.ReceiveDataService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.server.standard.ServerEndpointExporter;

import javax.annotation.PostConstruct;

/**
 * @author 12077
 */
@Configuration
public class WebSocketConfig {

    /**
     * 注入一个ServerEndpointExporter,该Bean会自动注册使用@ServerEndpoint注解申明的websocket endpoint
     */
    @Bean
    public ServerEndpointExporter serverEndpointExporter() {
        return new ServerEndpointExporter();
    }
}

package com.cosmo.sandtable.websocket;
import com.cosmo.sandtable.service.ReceiveDataService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.atomic.AtomicInteger;
/**
 * 前后端交互的类实现消息的接收推送(自己发送给所有人(不包括自己))
 *
 * @author 12077
 * @ServerEndpoint(value = "/test/oneToMany") 前端通过此URI 和后端交互，建立连接
 */
@Slf4j
@ServerEndpoint(value = "/sandTable")
@Service
public class OneToManyWebSocket {

    /**
     * 记录当前在线连接数
     */
    private static AtomicInteger onlineCount = new AtomicInteger(0);

    /**
     * 存放所有在线的客户端
     */
    private static Map<String, Session> clients = new ConcurrentHashMap<>();

    private static ReceiveDataService receiveDataService;

    /**
     * 解决authwire不能注入问题 ReceiveDataService
     * @param receiveDataService
     */
    @Autowired
    public void setApplicationContext(ReceiveDataService receiveDataService){
        OneToManyWebSocket.receiveDataService=receiveDataService;
    }

    /**
     * 连接建立成功调用的方法
     */
    @OnOpen
    public void onOpen(Session session) {
        onlineCount.incrementAndGet(); // 在线数加1
        clients.put(session.getId(), session);
        log.info("有新连接加入：{}，当前在线人数为：{}", session.getId(), onlineCount.get());
        receiveDataService.lightResetLoop(1);
    }

    /**
     * 连接关闭调用的方法
     */
    @OnClose
    public void onClose(Session session) {
        onlineCount.decrementAndGet(); // 在线数减1
        clients.remove(session.getId());
        log.info("有一连接关闭：{}，当前在线人数为：{}", session.getId(), onlineCount.get());
    }

    /**
     * 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
     */
    @OnMessage
    public void onMessage(String message, Session session) {
        log.info("服务端收到客户端[{}]的消息:{}", session.getId(), message);
        this.sendMessage(message, session);
    }

    @OnError
    public void onError(Session session, Throwable error) {
        log.error("发生错误");
        error.printStackTrace();
    }

    /**
     * 群发消息
     *
     * @param message 消息内容
     */
    private void sendMessage(String message, Session fromSession) {
        for (Map.Entry<String, Session> sessionEntry : clients.entrySet()) {
            Session toSession = sessionEntry.getValue();
            // 排除掉自己
            if (!fromSession.getId().equals(toSession.getId())) {
                log.info("服务端给客户端[{}]发送消息{}", toSession.getId(), message);
                toSession.getAsyncRemote().sendText(message);
            }
        }
    }

    public void sendMessage(String message) {
        for (Map.Entry<String, Session> sessionEntry : clients.entrySet()) {
            Session toSession = sessionEntry.getValue();
            toSession.getAsyncRemote().sendText(message);
        }
    }
}

websocket不能注入报空指针：https://blog.csdn.net/qq_40136782/article/details/109078750

https://www.cnblogs.com/xuwenjin/p/12664650.html