The content of element type "package" must match "(result-types?,interceptors?,default-intercept .

在编写后台登陆模块时，将许多默认的设置放在一个名为default的package
里。然后再定义其他package继承该包。之前我的struts.xml配置如下
<struts>
    <constant
name="struts.objectFactory" value="org.apache.struts2.spring.StrutsSpringObjectFactory"
/>
    <constant
name="struts.devMode" value="true" />
   
    <package
name="exam_default" extends="struts-default" namespace="/">
        <!--自定义拦截器及拦截器栈-->
        <interceptors>
            <!--用户认证拦截器-->
            <interceptor
name="authentication" class="action.admin.AuthenticationInterceptor"/>
             <!--用户认证拦截器栈，用于防止用户非法访问-->
            <interceptor-stack
name="user" >
                <interceptor-ref
name="authentication" />
                <interceptor-ref
name="defaultStack"/>
            </interceptor-stack>
            <interceptor-stack
name="guest" >
                <interceptor-ref
name="defaultStack"/>
            </interceptor-stack>
        </interceptors>
        <!--全局异常映射-->
        <global-exception-mappings>
            <exception-mapping
result="error" exception="java.lang.Exception"/>
        </global-exception-mappings>
       <!--全局result-->
        <global-results>
            <result
name="error">/error.jsp</result>
        </global-results>
    </package>
   
    <package
name="admin" extends="exam_default" namespace="/admin">
        <action
name="login" class="login">
            <result
type="redirectAction">index</result>