spring的依賴注入，為什么用接口的實現類而不是父類的繼承類？

@Resource
private EmployeeService employeeService;

public void setEmployeeService(EmployeeService employeeService) {
this.employeeService = employeeService;
}

報錯：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name '/login':

Injection of resource dependencies failed; nested exception is org.springframework.beans.factory.BeanNotOfRequiredTypeException:

Bean named 'employeeService' must be of type [com.xidian.service.imp.EmployeeService], but was actually of type [com.sun.proxy.$Proxy67]

 

改成接口方式：

@Resource
private EmployeeServiceInter employeeService;

public void setEmployeeService(EmployeeServiceInter employeeService) {
this.employeeService = employeeService;
}

就可以啦！

 

通常是service層需要aop。用接口的話，AOP可以使用java自帶的動態代理，但是有點麻煩要寫接口。用類就要用第三方包cglib，但是簡單，不用寫接口

jdk規定動態代理必須用接口；當然也可以用類，用cglib可以去處理就可以了。