Spring-Reactive samples - Mono and Single

This is just a little bit of a learning from my previous post where I had tried out the Spring's native support for  reactive programming.

Just to quickly recap, my objective was to develop a reactive service which takes in a request which looks like this:

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{  "id":1,   "delay_by": 2000,   "payload": "Hello",   "throw_exception": false }

and returns a response along these lines:

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{   "id": "1",   "received": "Hello",   "payload": "Response Message" }

I had demonstrated this in two ways that the upcoming Spring's reactive model supports, using the Reactor-Core Flux type as a return type and using Rx-java Observable type

However the catch with these types is that the response would look something like this:

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1	[{"id":"1","received":"Hello","payload":"From RxJavaService"}]

Essentially an array, and the reason is obvious - Flux and Observable represent zero or more asynchronous emissions and so Spring Reactive Web framework has to represent such a result as an array.

The fix to return the expected json is to essentially return a type which represents 1 value - such a type is the Mono in Reactor-Core OR a Single in Rx-java. Both these types are as capable as their multi-valued counterparts in providing functions which combine, transform their elements.

So with this change the controller signature with Mono looks like this:

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@RequestMapping(path = "/handleMessageReactor", method = RequestMethod.POST) public Mono<MessageAcknowledgement> handleMessage(@RequestBody Message message) {   return this.aService.handleMessageMono(message); }

and with Single like this:

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@RequestMapping(path = "/handleMessageRxJava", method = RequestMethod.POST) public Single<MessageAcknowledgement> handleMessage(@RequestBody Message message) {   return this.aService.handleMessageSingle(message); }

I have the sample code available in my github repo