Intercept and Call Original Method

[marinofernandes]

Hi, I'm trying to intercept a method call and then call the original code. However, when I add @supercall Callable<?> call to the intercepted method, I get the following exception:

Exception java.lang.IllegalArgumentException: None of [public static void ByteBuddyTest$Interceptor.enter(java.lang.Object[],ByteBuddyTest$MyClass,java.util.concurrent.Callable)] allows for delegation from public void ByteBuddyTest$MyClass.sayHello(java.lang.Object)

Do you know what am I missing in this code?

static {
    replaceMethodByteBuddy(MyClass.class, "sayHello", Interceptor.class);
}

public static void main(String[] args)
    throws Exception {

    new MyClass().sayHello("World");
}

public static class MyClass {

    public void sayHello(Object name) {
        System.out.println("Hello ");
    }
}

public static void replaceMethodByteBuddy(Class originalClass,
                                          String originalMethod,
                                          Class replaceClassWithOverwriteMethod) {
    try {

        ByteBuddyAgent.install();
        new ByteBuddy()
            .redefine(originalClass)
            .method(named(originalMethod))
            .intercept(MethodDelegation.to(replaceClassWithOverwriteMethod))
            .make()
            .load(originalClass.getClassLoader(), ClassReloadingStrategy.fromInstalledAgent());
    }
    catch (Exception e) {
        System.out.println("Exception " + getException(e));
    }
}

public static class Interceptor {

    public static void enter(@AllArguments Object[] allArguments,
                             @This MyClass self,
                             @SuperCall Callable<?> call) {
        System.out.println("Before interception");
        System.out.println("Arguments: ");
        try {
            call.call();  // Invokes the original method
        }
        catch (Exception e) {
            throw new RuntimeException(e);
        }
        System.out.println("After interception");
    }
}

}

`

[raphw]

You are likely looking for rebase, not redefine as the latter fully replaces the targeted method.

[marinofernandes]

Thanks Raphw!
If I just replace redefine by rebase I get the following exception:
Exception java.lang.UnsupportedOperationException: class redefinition failed: attempted to add a method at sun.instrument.InstrumentationImpl.retransformClasses0(Native Method) at sun.instrument.InstrumentationImpl.retransformClasses(InstrumentationImpl.java:144) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at net.bytebuddy.utility.Invoker$Dispatcher.invoke(Unknown Source) at net.bytebuddy.utility.dispatcher.JavaDispatcher$Dispatcher$ForNonStaticMethod.invoke(JavaDispatcher.java:1032) at net.bytebuddy.utility.dispatcher.JavaDispatcher$ProxiedInvocationHandler.invoke(JavaDispatcher.java:1162) at net.bytebuddy.dynamic.loading.$Proxy19.retransformClasses(Unknown Source) at net.bytebuddy.dynamic.loading.ClassReloadingStrategy$Strategy$2.apply(ClassReloadingStrategy.java:399) at net.bytebuddy.dynamic.loading.ClassReloadingStrategy.load(ClassReloadingStrategy.java:227) at net.bytebuddy.dynamic.TypeResolutionStrategy$Passive.initialize(TypeResolutionStrategy.java:101) at net.bytebuddy.dynamic.DynamicType$Default$Unloaded.load(DynamicType.java:6325)

[raphw]

I see now that you are using reloading. This brings some limitations. Have a look at AgentBuilder which allows you to register a listener to class loading which applied the transformation prior.

Alternatively, have a look at Advice over Method delegation.