[splix]

Here is what we use and I'd recommend to others.

The most common: - Kotlin for most of the backend code, but Java for shared libs. We still use Java 8 for some libs which may be used in Android, that's an unfortunate reality

- Gradle for build config

- Spring for application architecture

And few things that may significantly improve your dev process, but are not so common:

- Spring Reactor (and Webflux) for processing data and requests. Takes a time to learn, but it worth it

- Thymeleaf for UI

- Spock for testing. Highly recommended for designing tests

- Testcontainers for integration tests

- Micrometer to see what's going on with your app. I.e., to export all internal metrics to use with Prometheus/Grafana/etc

For the environment

- SDKMan to manager the environment

- Gradle Application plugin or Google's Jib to pacakge your app. First prepares a Zip with all binaries, second a Docker container

- IntelliJ IDEA

- Github Actions - turns out to be the most usable CI. Though the Jetbrains TeamCity may be better for a large team

[farmerbb]

> Kotlin for most of the backend code, but Java for shared libs. We still use Java 8 for some libs which may be used in Android, that's an unfortunate reality

Considering Kotlin is a supported, first-class language on Android, why not write your shared libs in Kotlin as well?

[splix]

I'm talking about open-source libs, i.e., I don't know who is going to use the lib, which env and target language they have, etc.

So I think that Java is the best middle ground here because it guaranties the full support of JVM features and 3rd party tools. I mean just avoiding a risk that it would be incompatible with something.