@Autowired注入

1、根据类型找到对象注入

        @Autowired
        private UserService userService;

2、set方法注入

    private UserService userService;
    @Autowired
    public void setUserService(UserService userService) {
        this.userService = userService;
    }

3、构造方法注入

    private UserService userService;
    @Autowired
    public UserControlller(UserService userService) {
        this.userService = userService;
    }

4、形参上注入

    private UserService userService;
    
    public UserControlller(@Autowired UserService userService) {
        this.userService = userService;
    }

5、只有一个有参构造，无注解

    private UserService userService;

    public UserControlller( UserService userService) {
        this.userService = userService;
    }

6、根据名称注入

    @Autowired
    @Qualifier(value = "userServiceImpl")
    private UserService userService;