Spring Stomp 可以发送未经请求的消息 [英] Spring Stomp CAN send unsolicited messages

问题描述

在 Spring WebSocket 文档中我发现了这句话:

In the Spring WebSocket docs I found this sentence:

重要的是要知道服务器不能发送未经请求的消息.

It is important to know that a server cannot send unsolicited messages.

http://docs.spring.io/spring/docs/current/spring-framework-reference/html/websocket.html(25.4.1)

不过我试过这个代码:

@Controller
public class WebsocketTest {

    @Autowired
    public SimpMessageSendingOperations messagingTemplate;

    @PostConstruct
    public void init(){
        ScheduledExecutorService statusTimerExecutor=Executors.newSingleThreadScheduledExecutor();
        statusTimerExecutor.scheduleAtFixedRate(new Runnable() {                
            @Override
            public void run() {
                messagingTemplate.convertAndSend("/topic/greetings", new Object());
            }
        }, 5000,5000, TimeUnit.MILLISECONDS);
    }
}

并且消息按预期每 5000 毫秒广播一次.

And the message is broadcasted every 5000ms as expected.

那么为什么 Spring 文档说服务器不能发送未经请求的消息?

So why Spring docs says that a server cannot send unsollicited messages?

推荐答案

下一句可能意味着在 stomp.js 客户端中您需要设置订阅:

The next sentence might mean that in the stomp.js client you are required to set a subscription:

来自服务器的所有消息都必须响应特定客户端订阅

All messages from a server must be in response to a specific client subscription

但这并不一定意味着响应请求.例如，网络套接字可以将信息发送到以下内容:

But this does not necessarily mean in response to a request. For example a web socket could send information to the following:

Javascript:

stompClient.subscribe('/return/analyze', function(data) {
    generateTableData(JSON.parse(data.body));
 });

春季:

@Autowired
private SimpMessagingTemplate simpMessagingTemplate;

public void sendSetpoint(String data) throws Exception {
    this.simpMessagingTemplate.convertAndSend("/return/analyze", data);
}

但是它不能向客户端发送未经请求的消息，除非该订阅存在.如果这是他们的意图，那就有点措辞不当.

But it cannot send unsolicited messages to the client unless that subscription exists. If this is their intended point it is a little poorly worded.

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