Library jar generation with only list of available methods and members

Question

Maybe someone can help me.
How can I generate a jar library similar to android.jar located in android sdk-platform. It should remove all methods implementations and replace it with throw new RuntimeException("Stub!"); like this:

AppWidgetManager() { throw new RuntimeException("Stub!"); }
public NdefMessage(NdefRecord[] records) { throw new RuntimeException("Stub!"); } 
public NdefRecord[] getRecords() { throw new RuntimeException("Stub!"); } 

All public members are also present.

Answer 1

If no one else gives a solution, it is a very simple case.

Simplest might be to use java's reflection, reading all classes from a jar and generate java source code.

Amd then there are libraries like ASM; byte code manipulation and also java dom source generation libraries.

Answer 2

A simple solution with javassist (I did not test, but roughly, this should be it):

ClassPool pool = new ClassPool();
pool.appendClassPath("pathToYourJar");
CtClass clazz = pool.get("Your class");

CtMethod throwingMethod = CtMethod.make("throw new RuntimeException();",clazz);

for(CtMethod method : clazz.getDeclaredMethods()){
    method.setBody(throwingMethod,null);
}

clazz.writeFile("pathToYourNewClassDirectory");



//zip the classes in your new class directory into a jar,
// add a manifest if you need to, deploy to where you want it