car1.run();
System.out.println("=================================");
Car car2 = extensionLoader.getExtension("sport", Utils.kv2Map(Wheel.class.getName(), "wood"));
car2.run(); // 缺省使用RubberWheel
System.out.println("=================================");
Car car3 = extensionLoader.getExtension(Utils.kv2Map(Car.class.getName(), "racing", Wheel.class.getName(), "wood"));
car3.run(); // 缺省使用RubberWheel