Comments on: Reactive REST API with Micronaut and MongoDB https://blog.codersee.com/reactive-rest-api-with-micronaut-and-mongodb/ Kotlin & Backend Tutorials - Learn Through Practice. Wed, 16 Apr 2025 04:50:05 +0000 hourly 1 By: Eric https://blog.codersee.com/reactive-rest-api-with-micronaut-and-mongodb/#comment-73 Fri, 25 Nov 2022 14:08:04 +0000 https://codersee.com/?p=5503861#comment-73 “nested” 🤔
That’s interesting. A flatmap untangles the nest. I like it!
Or maybe think of it like how a flat iron, that women use to straighten hair, gets rid of the curls. We’re eliminating data curliness 😆
These are great images to help me “untangle” the idea of a flatmap.

]]> By: Piotr https://blog.codersee.com/reactive-rest-api-with-micronaut-and-mongodb/#comment-72 Mon, 21 Nov 2022 16:38:08 +0000 https://codersee.com/?p=5503861#comment-72 In reply to Eric.

Of course agree with you, but I remember that I once saw on StackOverflow that someone explained it that “flat” is the opposite of “nested” and flattening is a removal of one nesting level 🙂
Since then it resonates a bit better with me 😁

]]> By: Eric https://blog.codersee.com/reactive-rest-api-with-micronaut-and-mongodb/#comment-71 Mon, 21 Nov 2022 16:08:20 +0000 https://codersee.com/?p=5503861#comment-71 Totally answered it! I think the “flatten” term here might be getting in the way? There’s probably not a better name, but the word “flat”, in this context, has never really resonated with me for some reason. Maybe something like “single” would make more sense to me? If you’re dealing with multiple dimensions of arrays, or in this case, a compounding of objects, and use flatMap, you’re really after a single array or single object. Unless something makes the word “flat” make sense to me, I think I’m calling this a singleMap (in my head), from now on 🙂

]]> By: Piotr https://blog.codersee.com/reactive-rest-api-with-micronaut-and-mongodb/#comment-70 Fri, 18 Nov 2022 15:24:37 +0000 https://codersee.com/?p=5503861#comment-70 In reply to Eric.

A reactive approach and to be more specific here- a Project Reactor definitely are worth learning (and even if we won’t use them in any project it’s a great way to strech our brains and think outside the box). On the other hand, this shift from a “standard” approach is a bit painful (and the infographics from the documentation do not help- at least in my case when I saw them for the first time 🙂).
Either way- as with probably every new technology- a bit of pain and sweat and it becomes easier.
Finally, answering the question (I know, I had to add a bit of storytelling 😏):

  • a map function takes a Function as an argument
  • a flatMap takes a Function<T, Publisher>

In the example above- the articleRepository.update function returns a Mono (which implements a Publisher), so we have to use the flatMap– otherwise we would end up with a Mono<Mono<T>> instead (just like flatMap in streams API flattens the structure and allows to avoid Stream<Stream> structure).
And maybe I wouldn’t use the term “flatten” in terms of the Project Reactor, I believe this comparison is a good way to start with in the beginning and gradually learn other concepts, like subscriptions etc.

Hope this answer helps (and even I sweated a bit when trying to describe it)! 😁

]]> By: Eric https://blog.codersee.com/reactive-rest-api-with-micronaut-and-mongodb/#comment-69 Fri, 18 Nov 2022 13:48:54 +0000 https://codersee.com/?p=5503861#comment-69 Another great one Piotr! It inspired me to pull up some info on Flux and Mono. I didn’t see the point at first given Java streams, but I now see the reason for their existence and they are quite powerful and useful. I will spend more time mining the depths of their capability. QUESTION: why flatmap vs. just map usage for the update function, for example? That function (and the others) is quite elegant, but makes my brain hurt a little 🙂

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