Javalin Framework for Kotlin and Java Updated
- By John K. Waters
- January 27, 2020
The latest release of Javalin, the lightweight Web framework for Kotlin and Java, is a minor, mostly bug-fix release, but the steady evolution and growing popularity of this open-source project are a kind of validation of this type minimalist framework.
A new version of Javalin has been released approximately twice a month (on average) since version 1.0 was released in November 2017. And all major releases have, so far, been backwards compatible.
This latest release adds a simple util class for rate limiting, letting devs call it in the beginning of their endpoint Handler functions. There's also a new plugin: RedirectToLowercasePathPlugin, designed to fill the void left by removing case-insensitive matching that was present in Javalin 2.x. The plugin redirects requests with uppercase/mixcase paths to lowercase paths. For example: /Users/Mary redirects to /users/Mary, if endpoint is /users/:userId. It doesn't affect the casing of path-params and query-params; just static URL fragments (Users becomes users above, but May remains Mary). When using this plugin, the documentation warns, you can only add paths with lowercase URL fragments.
Javalin first emerged as a fork the Spark Framework, another simple Java/Kotlin Web framework, but the project evolved quickly into a "ground-up rewrite" influenced by express.js, an unopinionated, minimalist web framework for Node.js. The framework runs on Eclipse Jetty, one of the most used and stable Web servers on the JVM.
Because Javalin was developed with compatibility in mind, the way it's used to build apps in Java and Kotlin are the same.
The Javalin project code files and details are available on GitHub. A complete list of the changes can be found here.
John K. Waters is the editor in chief of a number of Converge360.com sites, with a focus on high-end development, AI and future tech. He's been writing about cutting-edge technologies and culture of Silicon Valley for more than two decades, and he's written more than a dozen books. He also co-scripted the documentary film Silicon Valley: A 100 Year Renaissance, which aired on PBS. He can be reached at [email protected].