Ivo Limmen

Changing a private variable for testing

Sometimes you just need to update the value of a static private variable for junit testing. It often is a code smell if this is needed, in this case as well but it was not allowed to redesign the software. So we made a reflection utility class that can change the values:

public static void setStaticPrivateVariable(Class<?> objectClass,
		String fieldName, Object value) throws Throwable {

	Field field = objectClass.getDeclaredField(fieldName);
	field.setAccessible(true);

	Field modifiersField = Field.class.getDeclaredField("modifiers");
	modifiersField.setAccessible(true);
	int modifiers = modifiersField.getInt(field);

	if (Modifier.isFinal(modifiers)) {
		modifiers &= ~Modifier.FINAL;
		modifiersField.setInt(field, modifiers);
	}

	field.set(null, value);
}