Accessing fields on parameters of instrumented method using ByteBuddy

Question

I am trying to generate efficient property accessors at runtime. Specifically this means I am generating classes that implement the following interface using ByteBuddy:

interface PropertyAccess<T> {
    void set(Object instance, T value);
    T get(Object instance);
}

Implementations should look something like this:

class SomeProperty implements PropertyAccess<String> {
    public void set(Object o, String s) {
        ((SomeClass) o).setFoo(s);
    }
    public String get(Object o) {
        return ((SomeClass) o).getFoo();
    }
 }

Doing this for a getter/setter pair is easy ( getter and setter being the java.lang.reflect.Method objects for the actual getter and setter):

new ByteBuddy()
    .subclass(Object.class)
    .implement(PropertyAccess<String>.class) // pseudo syntax, I am using Guava's TypeToken here in reality
    .method(named("get")).intercept(invoke(getter).onArgument(0))
    .method(named("set")).intercept(invoke(setter).onArgument(0).withArgument(1))

(I left out here the assigner typing that will allow the cast from Object to SomeClass ).

But now I want to also allow generating such a class for a directly accessed field and I cannot find a way to do so without writing a custom Implementation class, because FieldAccessor only allows access to fields of the generated class (or one of it's parents).

Am I missing something?

Answer 1

You are right, there is currently no way to access a field rather then a method. I think this should however be easy to fix by treating a field access similar to a getter or setter. I am tracking this limitation in ticket #225 .