Unable to instantiate Action, action.UsersAction, defined for 'Users_login' in

<!--?xml version="1.0" encoding="UTF-8" ?-->

今天遇到一个很奇葩的问题，就是我在没有动过struts.xml情况下，无端端地执行action会出现下面的情况：

Unable to instantiate Action, action.UsersAction,  defined for 'Users_login' in 
namespace '/users'action.UsersAction - action - file:/D:/tomcat/webapps/Sapt/WEB-INF/
classes/struts.xml:12:63
而且执行登陆的action也是没有问题的，以下是我的struts.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
	"-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
	"http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>
	<constant name="struts.i18n.encoding" value="UTF-8" />
	<package name="default" namespace="/" extends="struts-default">

	</package>
	<package name="users" namespace="/users" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
		<result name="login_success">/users/Users_login_success.jsp</result>
		<result name="login_failure">/users/Users_login.jsp</result>
		<result name="logout_success">/users/Users_login.jsp</result>
		<result name="input">/users/Users_login.jsp</result>
		</action>
	</package>

	<package name="students" namespace="/students" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
		<result name="query_success">/students/Students_query_success.jsp</result>
		<result name="add_success">/students/Students_add_success.jsp</result>
		<result name="save_success">/students/Students_modify_success.jsp</result>
		<result name="save_fail">/students/Students_modify_fail.jsp</result>
		<result name="modify_success">/students/Students_modify.jsp</result>
		<result name="queryone_success">/students/Students_queryone.jsp</result>
		<result name="Query_result">/students/Students_Query_result.jsp</result>
		<result name="Query_noresult">/students/Students_Query_noresult.jsp</result>
		<result name="delete_success" type="chain">Students_query</result>
		<result name="Login_success">/students/Students_login_success.jsp
		</result>
		<result name="Login_failure">/students/Students_login.jsp</result>
		<result name="add_student">/students/Students_add.jsp</result>
		<result name="input">/students/Students_add.jsp</result>
<result type="redirect" name="add_student_success">/students/Students_add.jsp</result>
<result type="redirectAction" name="selectByCondition">Students_selectByCondition.action</result>
		</action>
	</package>

	<package name="webStudent" namespace="/webStudent" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
		<result name="input">/webStudent/webStudent_inputExcel.jsp</result>
	<result name="inputExcel_success">/webStudent/webStudent_inputExcel_success.jsp
		</result>
	<result name="inputExcel_failed">/webStudent/webStudent_inputExcel_failed.jsp
		</result>
		</action>
	</package>
	<package name="score" namespace="/score" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
	<result name="scoreQuery_success">/score/Score_query_success.jsp</result>
	<result name="addScore_success">/score/AddScore_success.jsp</result>
		<result name="updateScore_success">/score/UpdateScore_success.jsp</result>
		</action>
	</package>

	<package name="sign" namespace="/sign" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
			<result name="AddSign_success">/sign/AddSign.jsp</result>
		</action>
	</package>

	<package name="database" namespace="/database" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">

		</action>
	</package>
	<package name="excel" namespace="/webScore" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
			<result name="success">/score/listUI.jsp</result>
		</action>
	</package>

	<package name="class" namespace="/class" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
			<result name="listUI">/class/listUI.jsp</result>
			<result name="listStudentUI">/class/listStudentUI.jsp</result>
			<result name="input">/class/addUI.jsp</result>
	<result type="redirectAction" name="listUIAction">Class_listUI.action</result>
		</action>
	</package>

	<package name="scores" namespace="/scores" extends="default">
		<action name="*_*" class="action.{1}Action" method="{2}">
			<result name="listUI">/score/listUI.jsp</result>
			<result name="listClassUI">/score/listClassUI.jsp</result>
		</action>
	</package>

</struts>

然后我就按照它提示的路径打开tomcat里的struts.xml，发现内容没错啊。我猜系myeclipse sort佐，重启一下就ok了。