【C015054】使用构造器实现依赖注入的配置方式（）。

• A.<bean id="userService" class="com.ky.service.UserService">
  
   <constructor-arg ref="userDao">
  
   </constructor-arg>
  
  </bean>

• B.<bean id="userService" class="com.ky.service.UserService"  constructor-arg ref="userDao">
  
  </bean>

• C.<bean id="userService" class="com.ky.service.UserService">
  
   <property name="userDao" ref="userDao"></property>
  
  </bean>

• D.<bean id="userService" class="com.ky.service.UserService"  ref=”userDao”>
  
  </bean>