问个关于spring注解的问题 为什么测试类中不能用注解装配？

比如这是我的测试类 public class Test{ private Dao dao; private Person p; @Autowired public void setDao(Dao dao){ this.dao=dao; } @Autowired public void setP(Person p){ this.p=p; } public static void main(String[] args){ dao.s... 比如这是我的测试类 public class Test{ private Dao dao; private Person p; @Autowired public void setDao(Dao dao){ this.dao=dao; } @Autowired public void setP(Person p){ this.p=p; } public static void main(String[] args){ dao.save(p); } 运行后会报错是空指针 为什么？autowired不是已经赋值了么？