使用spring-boot-starter-websocket构建前后台通信。

1.导入spring-boot-starter-websocket的jar包

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

2.session信息维护类

@Slf4j
public class WebSocketSessionManager {
    /**
     * 保存连接 session 的地方
     */
    public static ConcurrentHashMap<String, WebSocketSession> SESSION_POOL = new ConcurrentHashMap<>();

    /**
     * 添加 session
     *
     * @param key
     */
    public static void add(String key, WebSocketSession session) {
        // 添加 session
        SESSION_POOL.put(key, session);
    }

    /**
     * 删除 session,会返回删除的 session
     *
     * @param key
     * @return
     */
    public static WebSocketSession remove(String key) {
        // 删除 session
        return SESSION_POOL.remove(key);
    }

    /**
     * 删除并同步关闭连接
     *
     * @param key
     */
    public static void removeAndClose(String key) {
        WebSocketSession session = remove(key);
        if (session != null) {
            try {
                // 关闭连接
                session.close();
            } catch (IOException e) {
                // todo: 关闭出现异常处理,添加错误处理逻辑
                e.printStackTrace();
            }
        }
    }

    /**
     * 获得 session
     *
     * @param key
     * @return
     */
    public static WebSocketSession get(String key) {
        // 获得 session
        return SESSION_POOL.get(key);
    }
}

3.websocket消息处理类

@Component
@Slf4j
public class WebSocketHandler extends AbstractWebSocketHandler {

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        //socket连接成功后触发
        log.info("建立websocket连接");
        WebSocketSessionManager.add(session.getId(), session);
    }

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        // 客户端发送普通文件信息时触发
        log.info("发送文本消息");
        // 获得客户端传来的消息
        String payload = message.getPayload();
        log.info("服务端接收到消息 " + payload);
    }

    @Override
    protected void handleBinaryMessage(WebSocketSession session, BinaryMessage message) throws Exception {
        //客户端发送二进信息是触发
        log.info("发送二进制消息");
    }

    @Override
    public void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {
        //异常时触发
        log.error("异常处理");
        WebSocketSessionManager.removeAndClose(session.getId());
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        // socket连接关闭后触发
        log.info("关闭websocket连接");
        WebSocketSessionManager.removeAndClose(session.getId());
    }
}

4.websocket配置类

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {

    @Autowired
    private WebSocketHandler webSocketHandler;

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
        registry
                .addHandler(webSocketHandler, "/msg")//websocket连接地址 ws://localhost:8080/msg
                //允许跨域，方便本地调试，生产建议去掉
                .setAllowedOrigins("*");
    }
}

 5.websocket操作相关服务类

@Service
@Slf4j
public class WebSocketService {

    /**
     * 发送消息
     *
     * @param session
     * @param text
     * @return
     * @throws IOException
     */
    public void sendMsg(WebSocketSession session, String text) throws IOException {
        session.sendMessage(new TextMessage(text));
    }

    /**
     * 广播消息
     *
     * @param text
     * @return
     * @throws IOException
     */
    public void broadcastMsg(String text) throws IOException {
        for (WebSocketSession session : WebSocketSessionManager.SESSION_POOL.values()) {
            session.sendMessage(new TextMessage(text));
        }
    }

}

6.项目启动类

@SpringBootApplication
@EnableScheduling
public class WebSocketApplication {

    public static void main(String[] args) {
        SpringApplication.run(WebSocketApplication.class, args);
    }

}

7.定时测试向浏览器发送消息类

@Slf4j
@Component
public class MessageJob {
    @Autowired
    WebSocketService webSocketService;

    /**
     * 每5s发送
     */
    @Scheduled(cron = "0/2 * * * * *")
    public void run(){
        try {
            webSocketService.broadcastMsg("服务端消息 "  + LocalDateTime.now().toString());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

8.启动如报如下错误，增加定时任务配置类

org.springframework.beans.factory.BeanNotOfRequiredTypeException: Bean named 'defaultSockJsTaskScheduler' is expected to be of type 'org.springframework.scheduling.TaskScheduler' but was actually of type 'org.springframework.beans.factory.support.NullBean'

@Configuration
public class ScheduledConfig {

    @Bean
    public TaskScheduler taskScheduler() {
        ThreadPoolTaskScheduler scheduling = new ThreadPoolTaskScheduler();
        scheduling.setPoolSize(10);
        scheduling.initialize();
        return scheduling;
    }
}

9.测试http://coolaf.com/tool/chattest在线工具进行调试