Struts2 注入属性错误，实例化action失败

Struts Problem Report
Struts has detected an unhandled exception:

Messages: No unique bean of type [com.ideasmaker.service.user.impl.UserServiceImpl] is defined: Unsatisfied dependency of type [class com.ideasmaker.service.user.impl.UserServiceImpl]: expected at least 1 matching bean
Error creating bean with name 'userAction': Injection of resource methods failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [com.ideasmaker.service.user.impl.UserServiceImpl] is defined: Unsatisfied dependency of type [class com.ideasmaker.service.user.impl.UserServiceImpl]: expected at least 1 matching bean
Unable to instantiate Action, userAction, defined for 'login' in namespace '/'Error creating bean with name 'userAction': Injection of resource methods failed; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No unique bean of type [com.ideasmaker.service.user.impl.UserServiceImpl] is defined: Unsatisfied dependency of type [class com.ideasmaker.service.user.impl.UserServiceImpl]: expected at least 1 matching bean 

该异常是因为action在实例化的时候注入属性出现依赖的UserServiceImpl的类型不唯一，这个时候注入的Service的类型应该是它的接口，也就是说要注入的UserServiceImpl的类型应该是它实现的接口，只要把UserServiceImpl修改为它实现的接口类型即可