Rewrite Groovy code generation to Java

[mpkorstanje]

🤔 What's the problem you've observed?

The cucumber-java and cucumber-java8 module generate annotations and interfaces using a groovy script.

Unfortunately the groovy-maven-plugin doesn't support Java 17 source code yet (groovy/gmaven#28). While we currently only have to run on Java 17 for #2644 it is not unimaginable that at some point in the future we'll also want to compile our own source code with 17 as well.

✨ Do you have a proposal for making it better?

With the increased release cadence of Java it would be prudent to keep the technology stack shallow and remove the dependency on Groovy and Groovy related components al together. So replacing the whole stack with pure Java would be beneficial.

📚 Any additional context?

There is a small chicken and egg problem to solve. Generating code with Java requires that the Java code is compiled. However because we are generating code, nothing has been compiled yet.

[mpkorstanje]

It is possible to execute the maven-compile-plugin in the generate-sources phase. So it should be possible to compile the source generation code before executing it.

https://stackoverflow.com/a/43187728/3945473

[mlvandijk]

Potential templating engines:

• Apache Velocity
• Apache FreeMarker
• StringTemplate

[mlvandijk]

From quick search, FreeMarker looks to be the most popular / active, so I'll try that out.