javalin the lightweight java framework

2026-10-01T18:15:11Z

I'd like to introduce you all to Javalin. Java is known for being heavy and bloated, verbose, often flagged as bad choice for cold-start functions, or simple MVPs or POCs. Often because it's slow, or memory-heavy consumer, which I could agree with, on some situations.

This is specially interestring if you're coming from languages such as Go or Typescript and is already familiar with express.js or chi from Golang. The learning curve for a full Java backend app will be pretty smoth.

Let's cut to the chase, no rambling, no time spent. Javalin is simple, lightweight, interoperable, flexible, supports OpenAPI and runs on top of Jetty JVM web-server, that includes SSL and HTTP3.

Here's what a Hello World would look like, if you're curious.

import io.javalin.Javalin;

void main() {
  var app = Javalin.create(config -> {
    config.routes.get("/", ctx -> ctx.result("Hello World"));
  }).start(7070);
}

And that's it! No annotations needed, controllers, or any of the boilerplate that Springs like. As simple as that.

If you're a maven person, you can get started in the maven-setup page, but ify you're a graddle person, use the graddle-setup page.

On their page there's plenty of useful tutorials and code snippets, check it out. And now if you want to go straight to the code, find their GitHub repo at: https://github.com/javalin/javalin

Native build

Javalin also supports GraalVM. GraalVM builds are OS-native binaries, compiled into full executable apps that can run without the JVM. This is super attractive for Serverless and functions that needs cold-start within seconds.

Here's an example from their main page: https://javalin.io/2018/09/27/javalin-graalvm-example.html and if you want something more complete, including tests, Flyway migrations, and more, you can take a look at this personal project: https://github.com/thermcampos/lin-order-java.

That's all for today. If you have any questions, I'll be happy to answer. Reach out by using the comment system below or any of the link in the about page.

Thanks for reading.

thermcampos blog » java

javalin the lightweight java framework

Native build