5 Best Kotlin Server-side Frameworks

Kotlin is a new programming language, which has been already reported by Google as a “first- class” language supported on Android. Although, it is continually being developed and improved, Kotlin is already considered a mature ecosystem and its popularity is growing rapidly, particularly with the mobile development. Everything necessary is done with just installing the Kotlin Plugin and allowing it to configure your project.

Kotlin is a great fit for developing server-side applications, allowing you to write concise and expressive code while maintaining full compatibility with existing Java-based technology stacks and a smooth learning curve:

Features of Kotlin-

Expressiveness- 

Kotlin’s innovative language features, for example, its support for type- safe builders and delegated properties, help build powerful and simple to use abstractions.

Scalability-

Kotlin’s support for coroutines which helps to build server-side applications that scale to huge numbers of clients with modest hardware requirements.

Interoperability:

Kotlin is fully compatible with all Java- based frameworks, which gives you a chance to stay on your familiar technology stack while gaining the benefits of more modern language.

Tooling:

Kotlin offers framework-specific tooling (for example, for Spring) in the plugin for IntelliJ IDEA Ultimate.

Learning Curve:

For a Java developer, getting started with Kotlin is very easy. The automated Java to Kotlin converter included in the Kotlin plugin helps with the first steps. Kotlin Koans offer a guide through the key features of the language with a series of interactive exercises.

Top 5 Kotlin server-side frameworks-

1. Javalin-

Basically, Javalin is just a few thousand lines of code over Jetty. It began as a fork of the Java and also Kotlin web framework Spark, which immediately turned into a ground- up rewrite influenced by the Javascript framework koa.js. Since the first release, A new version is released two times per month (overall), where each non-major version is backward compatible.

Advantages-

  • It centers around completing things rapidly. In some cases this doesn’t feel like an advantage
  • Simple to use
  • Embedded Jetty server
  • Lightweight and fast, especially compared to other counterparts here.
  • Lambda- based WebSocket API
  • Real micro- framework

Limitations-

  • Documentation is not a great. While suitable for someone with a prior Javalin knowledge; it simply not good for someone who simply needs to learn from scratch. 
  • Not sticking to standard terminology. For instance, what is normally known as Routes and Filters are combined together as Handlers. Which makes it harder when you read outsider tutorials and people keep referring to it as routes or filters.
  • Not develop enough; their feature to-do list is still excessively long. To battle this you should depend on outsider dependencies and that is an extremely profound gap. 

2. KTor-

Ktor is a framework for rapidly making web applications in Kotlin with minimal effort. It is very light and don’t impose any constraints on what underlying technology a project is going to use. What makes it stand up is that it’s created by the Kotlin team. 

Advantages

  • Reliable and stable
  • Small memory footprint and lightweight
  • Fast but competition is faster (like Javalin and http4d)
  • Perfect for prototyping
  • Real micro-framework

Limitations-

  • Experiences a similar issue as Javalin. If you have to make anything complex you should incline toward third-party libraries.
  • If you do not know what are you doing then documentation is going to be confusing as hell.
  • Not mature enough
  • Small community

3. Spark-

Spark is the typical suspect with regards to micro-services. It’s one of the oldest expressive Kotlin/ Java web framework built for rapid development, you can even consider it a higher level of Kotlin frameworks. Really awful the support is still in the alpha version.

Advantages-

  • Small memory footprint
  • Fast and also a lightweight
  • Excellent for rapid prototyping
  • Easy to setup
  • Plays well with Angular
  • Real micro-framework
  • Embedded Jetty server

Limitations-

  • Documentation could be better, it is not intended for beginners.
  • Not appropriate for large projects. 

4. Spring Boot-

Spring Boot makes it easy to create stand- alone, production- grade Spring based Applications that you can “just run”.

Advantages-

  • Can create stand- alone spring applications
  • Easy to setup and handle
  • Spring family environment
  • Modular
  • Plays well with other libraries
  • Large community (very popular)
  • Enterprise-ready

Limitations-

  • Documentation fragmentation. Too many sources, too many versions, too many differences. Make sure you know which version you are going to use.
  • Breaking changes between versions. If you hate what Angular is doing you will also hate it here.
  • Confusing documentation. 

5. Vert.x-

Vert.x is a tool- kit for building reactive applications in a different programming language, like Java and Kotlin. This tool (kit) is powerful, however, it is not for everyone. Keep reading and you will find why.

Advantages-

  • Fast
  • Small memory footprint – Comparable to Spark
  • WebSockets support
  • Reactive systems approach. The idea is to have more flexible, loosely-coupled and scalable applications.
  • Vert.x offers a complete ecosystem
  • Highly modular

Limitations-

  • It’s not for everybody. As a reactive toolkit, it fills a different niche compared to other frameworks here. 
  • Not a solution for you if the Spring Boot is your framework of choice. Before you try it make sure you know what are you getting into.

Conclusion-

Just like with Java, this comparison is a fight between well- established all-around frameworks and their more lean micro-service counterparts. Here we’ve listed out some advantages and also limitations of each framework. Know the comparison between Kontin and Java at- Kotlin vs Java. You can select the best one among these as per your requirement.

Selecting the best framework leads to the success of project. So choosing an appropriate framework for server-side development is cruical task. Are you facing a problem to decide the framework for server-side? You can consult with Solace experts to select the best one. Well experienced team is here to help you for that eases your development.