Using WebSocket to build an interactive web application
============================================================

.. code-block:: java

    package com.example.messagingstompwebsocket;

    import org.springframework.messaging.handler.annotation.MessageMapping;
    import org.springframework.messaging.handler.annotation.SendTo;
    import org.springframework.stereotype.Controller;
    import org.springframework.web.util.HtmlUtils;

    @Controller
    public class GreetingController {


        @MessageMapping("/hello")
        @SendTo("/topic/greetings")
        public Greeting greeting(HelloMessage message) throws Exception {
            Thread.sleep(1000); // simulated delay
            return new Greeting("Hello, " + HtmlUtils.htmlEscape(message.getName()) + "!");
        }

    }

.. code-block:: java

    package com.example.messagingstompwebsocket;

    import org.springframework.context.annotation.Configuration;
    import org.springframework.messaging.simp.config.MessageBrokerRegistry;
    import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
    import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
    import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

    @Configuration
    @EnableWebSocketMessageBroker
    public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

        @Override
        public void configureMessageBroker(MessageBrokerRegistry config) {
            config.enableSimpleBroker("/topic");
            config.setApplicationDestinationPrefixes("/app");
        }

        @Override
        public void registerStompEndpoints(StompEndpointRegistry registry) {
            registry.addEndpoint("/gs-guide-websocket").withSockJS();
        }

    }

`@EnableWebSocketMessageBroker`: enables WebSocket message handling, backed by a message broker.


config.enableSimpleBroker("/topic"): 订阅Broker名称，可以开启多个，例如："/topic","queue"

setApplicationDestinationPrefixes：全局使用的消息前缀（客户端订阅路径上会体现出来）

.. code-block:: javascript

    function sendName() {
        stompClient.send("/app/hello", {}, JSON.stringify({'name': $("#name").val()}));
    }

在客户端侧，使用stompClient发送消息时，需要指定一个前缀/app。