CODEWITHSUNDEEP
javaandroidantlr4byte-buddy
loloof64
loloof64

Reputation: 5392

Override a class method from a string with byte-buddy?

Let's say I have the following class (or can it be done with an interface also ?) :

class MyCustomClass {
    boolean myCustomMethod(int a, int b){}
}

And the following string :

Math.abs(a - b) >= 10;

Is there a way, with Byte Buddy, to inject the code from the string into a new subclass of MyCustomClass, in the method myCustomMethod ? Even if the String is processed with ANTLR before ?

So I get

class MyCustomClass_SubClassInstance extends MyCustomClass {
    // I know that with ByteBuddy, all this "ceremonial" code is not needed.
    boolean myCustomMethod(int a, int b){
         Math.abs(a - b) >= 10; // Injected code from the string
    }
}

Upvotes: 2

Views: 967

Answers (2)

Rafael Winterhalter
Rafael Winterhalter

Reputation: 44032

This is not the idea behind Byte Buddy. The Byte Buddy way of doing such a thing would be to implement a class that offers the method you want to invoke and then you generate a proxy to delegate to this method invocation from the instrumented type.

Javassist offers such functionaltiy but performance-wise, it is not great to compile strings at runtime so I would try to avoid this at all costs. Especially on Android where you typically have limited ressources. Class generation is quite expensive.

Upvotes: 2

GhostCat
GhostCat

Reputation: 140427

I think you are going down the wrong way. Why use ByteBuddy to generate class code?!

Instead: use the JavaCompiler feature to simply build that class as Java source - then compile it, then use the "dynamically" compiled class.

Meaning: you are somehow overcomplicating things. You actually know what you want to end up with - so create that as java source, and programmatically turn to javac to turn that into byte code.

For Android, the JavaSourceToDex class might be the thing to use.

Upvotes: 2

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