android-buddy VS Byte Buddy

That's what happened to me when I tried to write some bytecode transformations using Byte Buddy. I noticed that they wouldn't work for Android right away, and instead, some sort of adapter is needed in order to make the connection between these bytecode transforming tools and the Android compilation so that said transformations happen at compile time. Sadly for me, such compilation adapter didn't exist for Byte Buddy and Android, which is why I took the time to create one: Android Buddy.

As seen above, the API exposes the user to low-level bytecode manipulation via byte arrays. It would be unwieldy to do it directly. Hence, real-life projects rely on bytecode manipulation libraries. ASM has been the traditional library for this, but it seems that Byte Buddy has superseded it. Note that Byte Buddy uses ASM but provides a higher-level abstraction.

Just a drive-by comment: ByteBuddy is worth a look https://bytebuddy.net/. It is built on top of ASM.

> can you show an example of how you'd parse, say, a .java.in

The canonical way to do such a thing is through the java annotation processing api [1] and using a tool like java poet [2]. Before you did that, you'd probably decide if you wanted to instead use bytecode generation with a library like bytebuddy [3]

But, assuming for some reason, you wanted to torture yourself and actually consume a java.in file and apply a regex, then you'd probably pull out the "maven-replacer-plugin" [4] and configure that for the task at hand. (or use your favorite templating language plugin. There's a million of them).

Though, to be fair, this really isn't something that comes up in regular java programming due to the nature of the ecosystem. Anything you'd want to codegen likely already has a library and anything you didn't would receive (legitimate) push back.

[1] https://www.baeldung.com/java-annotation-processing-builder

[2] https://github.com/square/javapoet

[3] https://bytebuddy.net/

[4] https://github.com/beiliubei/maven-replacer-plugin

Have a look at byte buddy.

If you've ever used libraries like https://github.com/JakeWharton/hugo or https://hibernate.org/ (if you've ever done some backend development) and wondered how do they seem to add some code/logic into your app just by adding some annotation to some method, or if you ever wondered how mocking frameworks like Mockito can change a class behavior for example, then most likely you're interested in a programming technique that allows to modify existing code, usually known as Aspect oriented programming (also known in Java as Bytecode instrumentation) which, even though it might sound intimidating at first, some really cool tools such as Byte Buddy or AspectJ make it quite easy to accomplish.