Showing how to use reflection to test inner fields

realObjectFromField.java

	// Somewhere in a different utility class for testing
	@SuppressWarnings("unchecked")
	public static <T> T realObjectFromField(Class<?> clazz, String fieldName, Object object) {
		Field declaredField = accessibleField(clazz, fieldName);
		try {
			return (T) declaredField.get(object);
		} catch (IllegalArgumentException | IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

	private static Field accessibleField(Class<?> clazz, String fieldName) {
		try {
			Field declaredField = clazz.getDeclaredField(fieldName);
			declaredField.setAccessible(true);
			return declaredField;
		} catch (NoSuchFieldException | SecurityException e) {
			throw new RuntimeException(e);
		}
	}


	// This is how we use it in a test method
	import static mypackage.ReflectionUtils.realObjectFromField;
	
	ItemFiltersMapperByFlag mapper = realObjectFromField(ItemsFilterExecutor.class, "filtersMapper", filterExecutor);
	assertNotNull("mapper is null. Check wiring", mapper);