服务层上的异步 java 方法

Question

I'm using a library called PubNub for posting messages. The PubNub method posts messages asynchronously, and it has a way to see if the message was posted or not.

I'm using Spring MVC and ThymeLeaf, so I would like to send the response back to my front-end after I get the message status (error or success), however, I don't know how to wait until my PubNub method finishes, and then send the result. Here's the code:

    @Controller
    public class HomeController {
    
        @PostMapping("/triggerDevices")
        public String triggerDevices(@ModelAttribute(value = "message") Message message, Model model) {
        //
        //
        // validations and build data
        //
        //
         MyResult result = null;
    
         //Async method
                pubNub.publish()
                .message(message)
                .channel(channel)
                .async((result, status) -> {
                 //This block takes some time
                    if (status == null || status.isError()) {
                       //Error case
                       result = new MyResult (false, status.errorMessage(),message.device);
                    } else {
                       //Success case
                       result = new MyResult (true, null, message.device);
                    }
                });
    
            //Result
            model.addAttribute("result", result);
            return "home :: info-success";
       }  
    
    }

I hope someone helps me, thanks so much.

Answer 1

PubNub Java SDK Publish sync

Just use the sync method instead of async

PNPublishResult result = pubnub.publish()
                             .channel("coolChannel")
                             .message("test")
                             .shouldStore(true)
                             .ttl(10)
                             .sync();

See full PubNub SDK Java Docs for publish/sync .

That should do it for you. Cheers!

Answer 2

Using sync is an easy fix, but if u need to keep it async: i would return within the async function result here after you get the result:

//Success case
result = new MyResult (true, null, message.device);
model.addAttribute("result", result);
return "home :: info-success";