Invoke private static method with MethodUtils from Apache commons-lang3

Question

Is it possible to invoke a private static method with MethodUtils?

 LocalDateTime d = (LocalDateTime)MethodUtils.invokeStaticMethod(Service.class,
     "getNightStart",
      LocalTime.of(0, 0),
      LocalTime.of(8,0));

This code throws the exception:

java.lang.NoSuchMethodException: No such accessible method: getNightStart()

If I change method's access modifier to public it works.

Answer 1

No, because MethodUtils.invokeStaticMethod() calls Class.getMethod() under the hood. Even if you try to hack the modifier it won't be visible to the MethodUtils as it won't see the modified Method reference:

Service.class
  .getDeclaredMethod("getNightStart", LocalTime.class, LocalTime.class)
  .setAccessible(true);
MethodUtils.invokeStaticMethod(Service.class, 
   "getNightStart", LocalTime.of(0, 0), LocalTime.of(8, 0)); 

will still fail with NoSuchMethodException just like plain reflection:

Service.class
  .getDeclaredMethod("getNightStart", LocalTime.class, LocalTime.class)
  .setAccessible(true);
Method m = Service.class.getMethod("getNightStart", LocalTime.class, LocalTime.class);
m.invoke(null, LocalTime.of(0, 0), LocalTime.of(8, 0));

This will only work when the Method object is reused:

Method m = Service.class.getDeclaredMethod("getNightStart", LocalTime.class, LocalTime.class);
m.setAccessible(true);
m.invoke(null, LocalTime.of(0, 0), LocalTime.of(8, 0));