Invoke private static method with MethodUtils from Apache commons-lang3

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

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));