GH-599: Add support for GraalVM native images

artembilan commented 1 year ago

Fixes https://github.com/rometools/rome/issues/599

There is a lot of reflection in the project which probably has to be reworked this or other way eventually. But for now it is enough to have a proper reflection info exposed for GraalVM when it builds a native image for our application.

Used a native-image-agent to take a required native image config from the running sample application. More info in GraalVM docs: https://www.graalvm.org/22.0/reference-manual/native-image/Agent/. Works only if GraalVM is used to run the application, of course.

In general it is probably better to rework all the content of the rome.properties into a Java ServiceLoader API.

There is also too much clone() operations with reflection in the project: perhaps better to look into something like deep copy approach.

So, the fix is like this:

Add META-INF/native-image/romtools/resource-config.json to make all the properties from the project available for native image
Add META-INF/native-image/romtools/reflect-config.json for classes in the project used for reflection Mostly content of these files is generated by the mentioned above GraalVM agent
Remove LOG property from the CopyFromHelper since it is used only to log an error where we re-throw it immediately anyway. This was an attempt to see if initialize-at-build-time for some classes helps us somehow since there is a lot of static initialization, but turns out we still do that clone() with reflection, so pointless.

PatrickGotthard commented 1 year ago

Hi @artembilan,

can I merge this as-is to add support for GraalVM? I really have no time to dig deeper into this but at least I'm sure that this change does not break anything 🙃

Regards, Patrick

artembilan commented 1 year ago

You are right: it does not. As you see there is no code change , but this will help consumers of this project to be able to build GraalVM native images smoothly.

PatrickGotthard commented 1 year ago

Thanks for your contribution. I've merged it right now and all your mentioned improvements are planned for the future :)

artembilan commented 1 year ago

Good. Let me know when those changes are in, so I'll try it against native image and possibly contribute back according to a new state of matters.

rometools / rome

GH-599: Add support for GraalVM native images #636