There is no Action mapped for namespace /student and action

There is no Action mapped for namespace /student and action name classes_list.- [unknown location]
\x05
\x05\x05
\x05\x05\x05/WEB-INF/sample/student_list.jsp
\x05\x05
\x05\x05
\x05\x05\x05/WEB-INF/sample/classes_list.jsp
\x05\x05
\x05\x05
\x05\x05\x05/WEB-INF/sample/student_edit.jsp
\x05\x05\x05/WEB-INF/sample/student_edit.jsp
\x05\x05\x05student_list.do?currentPage=${currentPage}&operate=${operate}
\x05\x05\x05
\x05\x05
\x05\x05
student_*和manage_*可以访问,但是classes_*访问就会出现上面的提示.怎么会找不到list的映射文件呢,我几个写的一样,怎么student能访问classes就不能呢