Java enum anonymous inner class and reflection

Question

I have an enum with anonymous inner class like:

public enum Status {

    PRELIMINARY() {
    @Override
    boolean process() {
        return true;
    }

    SUBMITTED() {
    @Override
    boolean process() {
        return false;
    }

    abstract boolean process();

}

I have a model like

public class Foo {

    private Status status;

    public void setStatus(Status status) {
        this.status = status;
    }
}

I need to use reflection to set a Foo.status like:

private static <T> void setFieldValue(Foo instance, Class<?> klazz, Object value) {
    try {
        Class<?> aClass = value.getClass(); // Is Status$1 instead of Status
        Method method = klazz.getDeclaredMethod(getSetterName('setStatus'), aClass);
        method.invoke(instance, value);
    } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
        if (!klazz.equals(Object.class)) {
            setFieldValue(instance, klazz.getSuperclass(), fieldName, value);
        }
    }
}

This works when Status does not contain an inner class and is a simple enum, however for the above Status class it will throw a NoSuchMethodException . This is because the class of my value will be package.Status$1 instead of package.Status .

Is there a good work around for this?

Answer 1

You just need to change your means of locating the desired method. Something like the following should work:

private static @Nullable Method findMethod(Class<?> klass,
                                           final String methodName,
                                           final Object... args) {

    @Nullable Method candidate = null;

    classSearch:
    while (klass != null) {

        // Check all the class' methods for a matching one.
        methodSearch:
        for (final Method method : klass.getDeclaredMethods()) {
            if (!method.getName().equals(methodName)) continue;

            final Class<?>[] parameterTypes = method.getParameterTypes();
            if (parameterTypes.length != args.length) continue;

            // Check all parameters can come from the given args.
            for (int i = 0; i < args.length; i++) {
                if (!parameterTypes[i].isInstance(args[i])) continue methodSearch;
            }

            candidate = method;
            break classSearch;
        }

        // No matching method, check super class.
        klass = klass.getSuperclass();
    }

    // May be 'null' if no match was found.
    // Throw an Exception if this isn't a valid outcome in your case.
    return candidate;
}

Chaining this with your existing code (calling .invoke on the returned Method (if it's not null )) should give you the desired outcome.