添加依赖

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

添加配置类

@Configuration
public class WebSocketConfig {
    @Bean
    public ServerEndpointExporter serverEndpointExporter(){
        return new ServerEndpointExporter();
    }
}

添加服务类

@Component
@ServerEndpoint("/ws/{clientId}")
public class WebSocketServer {

    private static Map<String, Session> sessionMap = new HashMap<>();

    @OnOpen
    public void onOpen(Session session, @PathParam("clientId") String clientId) {
        System.err.println("客户端：" + clientId + "建立连结");
        sessionMap.put(clientId, session);
    }

    @OnClose
    public void onClose(@PathParam("clientId") String clientId) {
        sessionMap.remove(clientId);
    }

    /**
     * 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 clientId
     */
    @OnMessage
    public void onMessage(String message, @PathParam("clientId") String clientId) {
        System.err.println("收到来自客户端" + clientId + "的消息：" + message);
    }

    public void sendMessage(String message) {
        Collection<Session> sessions = sessionMap.values();
        for (Session session : sessions) {
            try {
                session.getBasicRemote().sendText(message);
            } catch (Exception e) {
                e.printStackTrace();
            }

        }
    }

}