Javalin 3.0 wishlist/discussion

This issue is for suggesting breaking changes.

I have one main thing on the list for Javalin 3, which is making it easier to create a JavalinServlet for use outside of Jetty. This means creating a separation between the server and the servlet (currently everything is lumped together in the Javalin class). It would be nice if this could support static files and file uploads.

This might make the initial setup slightly harder for the people who use Javalin with jetty (99%?), so we have to be very careful.

JavalinServlet could be released as a separate dependency, javalin-servlet, which javalin depends on.

Should also consider:

• Rewrite to Java (sadly, Kotlin interop isn’t as good as we thought)
• Interfaces for testing
• Reconsider plugin architecture. Currently they’re singletons (JavalinJson, JavalinRenderer). Maybe they should be put on the app.
• Remove case-insensitive path matching ?
• Do something about config? (ref #508)
• Do something about WsSession (also vs Context?)
• ~Rework casting and validation~ (DONE)
• Javalin logger to easily disable built in logging (in case people are building a framework on top?)

[wyatt-herkamp]

Rewrite to Java (sadly, Kotlin interop isn't as good as we thought) I know. Kotlin + Java causes issues when wanting Javadocs or documentation overall. So that will be nice.

[ghost]

1. Moving to Netty is 180 degrees shift in what Javalin always was, at least for me, so -1 here. (Asynchronous processing)
2. I’d vote against moving to Jetty 10 simply because of Java 11 requirement. There are still places where Javalin could be used, but its not possible to migrate from Java 8 since it brings effort and AdoptOpenJdk Azul IBM Amazon and others are still providing support for Java 8 and they will continue to do so for couple more years.
3. rewriting to Java can be an advertisement move, Kotlin users won’t even notice if we have a good wind, Java users who have their project’s requirements written in stone and vendor locked on Java might pick it up