LambdaMetaFactory boxing / unboxing parameters and return types

I've got the following two methods:

  public static <T, R> IGetter<T, R> createGetterViaMethodname( final Class<T> clazz, final String methodName,                                                                final Class<R> fieldType )      throws Throwable  {    final MethodHandles.Lookup caller = MethodHandles.lookup();    final MethodType methodType = MethodType.methodType( fieldType );    final MethodHandle target = caller.findVirtual( clazz, methodName, methodType );    final MethodType type = target.type();    final CallSite site = LambdaMetafactory.metafactory(        caller,"get",        MethodType.methodType( IGetter.class ),        type.erase(),        target,        type );    final MethodHandle factory = site.getTarget();    return (IGetter<T, R>) factory.invoke();  }  public static <T, I> ISetter<T, I> createSetterViaMethodname( final Class<T> clazz, final String methodName,                                                                final Class<I> fieldType )      throws Throwable  {    final MethodHandles.Lookup caller = MethodHandles.lookup();    final MethodType methodType = MethodType.methodType( void.class, fieldType );    final MethodHandle target = caller.findVirtual( clazz, methodName, methodType );    final MethodType type = target.type();    final CallSite site = LambdaMetafactory.metafactory(        caller,"set",        MethodType.methodType( ISetter.class ),        type.erase(),        target,        type );    final MethodHandle factory = site.getTarget();    return (ISetter<T, I>) factory.invoke();  }

including the following two interfaces:

@FunctionalInterfacepublic interface IGetter<T, R>{  @Nullable  R get( T object );}@FunctionalInterfacepublic interface ISetter<T, I>{  void set( T object, @Nullable I value );}

This works great for all Class-Types, including the Number-Wrappers for primitive types such as Integer for int. However, if I have a setter that takes an int or a getter that returns an ìnt, it tries passing / returning the Number-Wrapper, resulting in an exception.

What's the correct way to box / unbox this without having to make another method. The reason here is to keep the API clean and simple to use. I am willing to take a small performance hit for the boxing / unboxing here.