Command-line example for Helidon MP?

[lprimak]

Hi, I am trying to write a command-line app in Helidon MP using CDI.
No web server, jax-rs or alike is required.

However, I cannot find any example that does this. Every example is about running rest calls, or other MP features which I do not need for this, just CDI is a requirement.

My original application uses Weld SE, but I would like to try out native image with Helidon.

Thank you.

[lprimak]

Anybody? @danielkec @ljnelson my CDI fella? Please?

[ljnelson]

Note also: https://stackoverflow.com/a/67117216/208288 Not sure if we honor that when we did our repackaging etc.

[lprimak]

The helidon-microprofile-cdi + weld repackaging + helidon-mp-graal-native-image-extension did the trick.

Just wondering, there a way to initialize Weld SE directly without using helidon-microprofile-cdi? Or using some part of it?
The issue is that I want to use Weld version that's not the same as the one Helidon's "amazing repackaging" provides.

I figured out how to produce the same repackaging for different versions of Weld. However, am missing some magic that helidon-microprofile-cdi provides still to initialize Weld SE directly.

Thank you.

[danielkec]

👀 @tomas-langer

[lprimak]

Alright, I found they "key ingredient" Weld needs to be statically initialized at build-time (native image):

    static {
        container = new Weld()
                .addServices(new HelidonProxyServices())
                .initialize();
    }

This way, no runtime initialization is performed and it works!

[lprimak]

Further looking at the Weld ProxyFactory code in Helidon, could this be done cleaner via SubstrateVM Substitution mechanism by any chance?

[tomas-langer]

Problem with Substitutions in GraalVM is that they are not that much promoted by the team and are considered a "hackish" solution. It is always preferable to do it differently (ideally by modifying the original library).

[lprimak]

I have created https://github.com/flowlogix/weld-native which uses GraalVM substitutions and ByteBuddy for non-GraalVM situations to patch Weld the same way Helidon does, but without modifying any code directly or shaded version of Weld.

[lprimak]

What do you think @tomas-langer ?

[lprimak]

Hi, @tomas-langer @ljnelson
I have renamed the project to https://github.com/flowlogix/weld-native
What do you think? I would like to contribute this to Helidon, IMHO its cleaner than the current way Helidon patches Weld.

Thank you!

[lprimak]

Usage example is here: https://github.com/flowlogix/native-java/tree/main/helidon/helidon-greeter

[tomas-langer]

Great job! I know how complicated it can be to weld Weld and native-image together (pun intended).
This solution is not really an option for us in Helidon, as one of the main rules we stand by (in our codebase) is not to play tricks on the classes - so ByteBuddy is out of the question. Anytime bytecode manipulation happens, we get something different than the sources tell us, which makes troubleshooting much harder. Also this requires some assumptions to be made about the classpath that I prefer not to make

[lprimak]

Maybe you can reconsider since time has passed?
I now see many GraalVM substitutions in Helidon itself, which does exactly the same thing as ByteBuddy does for running Java code.

The only reason even to have ByteBuddy is to have the same functionality on the JVM as GraalVM substitution does in native image.