The MXBean specification says how certain parameterized types such as List<String> are handled, but does not say what happens with types that are not in this list. So for example, if I define...
    public class Whatsit<T> {
        public T getThing() {...}
    }
...then following the rules specified in javax.management.MXBean, I would expect "Mappings for other types" to apply, so that an MXBean interface like this...
    public interface SomeMXBean {
        public Whatsit<String> getA();
    }
...would define an attribute called A with the same type as if I had defined this...
    public class Whatsit {
        public String getThing() {...}
    }
    public interface SomeMXBean {
        public Whatsit getA();
    }
But the current implementation rejects this. Either the spec should be changed to rule out this case, or the implementation should be changed to accept it.