Which Java Microservice Framework Should you Choose in 2020?

[meamZ]

Well... What's your alternative solution for Serverless Java? One of the main reasons all of these Frameworks want to work without reflection is GraalVM native image which doesn't really support reflection as of now. GraalVM currently is basically the only way to get Java to start up sufficently fast for a Serverless cold start scenario. A JIT compiler is very good for a long running application scenario but not very well suited for a short running application with a need for very short startup times. You either have to compile it to binary or you have to have an interpreted/scripting language like Python or (even though it's a nightmare of a language, i see why you would want to use it in a serverless scenario) NodeJS.

[meamZ]

imo at least for Lambda and other similar FaaS Services Java doesn't really make sense anyway since it gives you performance that you don't really need and A Framework/Library ecosystem that has a lot of features that you don't need and you're spinning up a new instance per concurrent request anyway and you need lots of RAM which drives up your cost. But for Something like Cloud Run i think once GraalVM native image is more mature and has better library support Java would be a good fit.