
Kotlin and Jersey and Jetty and MongoDB – Creating a Scalable RESTful API - chernikovalexey
https://blog.gikken.co/kotlin-jersey-jetty-mongodb-creating-a-restful-api/
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ruffrey
I know these kinds of tutorials are just for getting a flavor of a framework
or paradigm. Nice so see it.

As someone who's used Mongo for nearly a decade, I always feel compelled to
note: Mongo will NOT scale with relational data like this. Sure, it can handle
a lot of records. It'll have fast basic inserts or queries. It can scale with
replicaSets and sharding. But it is NOT designed for relational data. Doing
relational data is so painful in Mongo, with any sort of scale. Save yourself
so much migration headache by using a "regular" SQL database, until it doesn't
work (rare).

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rumanator
That begs the question: what is Mongo's usecase?

~~~
tincholio
Web-scale stuff, of course!
[https://www.youtube.com/watch?v=b2F-DItXtZs](https://www.youtube.com/watch?v=b2F-DItXtZs)

Jokes aside, I had to do some analytics work at my last job, off data that was
on Mongo (arguably with no good reason, other than it being 'web scale'), and
it was a major pain.

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eatonphil
I like Jersey (and the standard API it implements: JAX-RS) a lot on its own
(as compared to using a larger framework like Spring). However it can be
difficult to program imperatively.

You'd expect in a compiled language like Java you'd figure out most of your
bugs during the type-checker pass. But there's so much implicit structure,
class loading, and annotations that make Jersey apps mostly dynamically typed.
You've got to compile and then hit every API endpoint/middleware to know it's
registered at all.

Even when you find the explicit APIs they are cumbersome to use, requiring
many lines of code for something that should be simple like imperatively
registering a route.

I put together my own notes on using Jersey, JOOQ (an ORM), and PostgreSQL a
month ago. My aim was to be as explicit as possible (though I did still have
to fall back on class loading a few times). [0]

[0] [http://notes.eatonphil.com/a-minimal-rest-api-in-
java.html](http://notes.eatonphil.com/a-minimal-rest-api-in-java.html)

~~~
Scarbutt
Was looking for a Java lightweight framework for an API and, there are so
many!

Javalin, Jooby, Spark, Micronaut and more, what do you like about Jersey over
these ones?

~~~
eatonphil
It's a vanilla implementation of JAX-RS. The rest of the libraries are
lightweight wrappers of JAX-RS with few committers or massive wrappers of JAX-
RS with a lot of development overhead. JAX-RS on its own is mostly at the
right level for me (with the exceptions mentioned).

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soulnothing
I really like Kotlin for full stack development. Unfortunately most shops are
still using Spring. Which I feel really limits the languages potential. I've
ended up on Vertx, but I am a bit concerned about it's lack of traction.

* Routes can be based off Open API (contract first), or a simple route via string

* First class GraphQL support

* Full ecosystem for DB, message bus, etc.

* PolyGlot, with a message bus and bindings for a number of different languages.

* For data persistence I use JaSync with a custom micro-orm, noted below. This provides non blocking async support.

With Kotlin multi platform, and typescript definitions in alpha. I can
generate the data classes to a typescript interface. Have my react project
pull those in, and use the data. If I need to do pub/sub over web sockets into
react that's also supported by Vertx. This drastically reduces bugs, and
developer time. As the data models are directly incremented and released with
the back-end. The front-end doesn't have to write additional code. The
Typescript project does need to install a kotlin dep, but that gets minimized.
A few kilobytes to ease development inter opt is worth it. The message bus
also does pub/sub to iOS/Android.

I've switched to kotlinx serialization. I have some parts running on native
llvm+clang, graal/jdk and nodejs. So I need the modules to be easily
serialized on different platforms.

This scales from a simple monolith. To if I need AOT compilation to Graal then
running through KNative. I generally start projects as a hybrid monolith. But
found it's scaled really well.

I'm really excited for the compiler api / arrow meta compiler. I'm looking
into ahead of time compilation of the queries. Automatically generating data
classes for more advanced queries. Think joins, or json aggs. Additionally
compiling the ORM calls into actual SQL strings.

* Multi platform kotlin micro orm (MariaDB + Postgres) only right now. Closest JDK analogy is Jooq.

[https://animusdesign.gitlab.io/kotlin-
frm/#/./sql](https://animusdesign.gitlab.io/kotlin-frm/#/./sql)

Editing formatting

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taude
A few years ago, I was really impressed with Vertx and wanted to use it for a
project. I was also into alternative JVM languages for awhile.

I feel like Java keeps getting better and better and the compelling argument
for the alt JVM languages is getting less interesting. (Except for something
like Cloujure which still looks super interesting to me.).

Thoughts from someone whos worked with Groovy/Grails, Scala/Play, Jython, and
Kotlin....

~~~
zmmmmm
> I feel like Java keeps getting better and better and the compelling argument
> for the alt JVM languages is getting less interesting

I keep going back to Java optimistically thinking the major problems will be
solved but it's always hell compared to coding in Kotlin or Groovy (which I
switch back and forth every couple of days). While it's true some fundamental
things have been addressed, there's just so much missing from the ergonomics
of Java that it is syntatically constrained from fixing, and philosophicaly
poorly positioned to address.

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st3fan
Great example of how to introduce a sql/mongo query injection in your code.

The string interpolation in findById will open up your whole database to the
world, possibly even allowing remote command execution.

Same for the other functions that access MongoDB.

Do not copy / paste random code until you fully understand it.

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sdinsn
> in findById

No, I'm pretty sure that's fine. findById takes an ID, not anything else or
any type of query.

~~~
st3fan
The code was updated after my comment.

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lf-non
I recently converted a spring project to use ktor+konform+exposed after
frustration with the number of errors that were not getting caught at compile
time.

Having mostly eliminated decorators & code generation I find my development
experience much more streamlined.

Kotlin DSLs are really nice to work with.

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pjmlp
> Hi! I spent a day making Jetty, Jersey, and MongoDB work together in Kotlin,
> that's why you won't have to!

And this is why platform languages win, there is nothing to spend time "making
it work".

