更改的代码如下：求大神指点

// 查询所有学生的动作

public String query() {

StudentsDAO studentsDAO = new StudentDAOImpl();

List<Students> list = studentsDAO.queryAllStudents();

// 放进session中

if (list != null && list.size() > 0) {

session.setAttribute("students_list", list);

}

System.out.println(list.size());

return "query_success";

}

<package name="students" namespace="/students" extends="default">

<action name="*_*" class="com.mr.action.{1}Action" method="{2}">

<result name="query_success">/students/Students_query_success.jsp</result>

</action>

</package>

<!-- #代表上下文栈 -->
	<s:iterator value="#session.students_list" var="stu">
		<tr class="list">
			<td><s:property value="#stu.sid"/></td>
			<td><s:property value="#stu.sname"/></td>
			<td><s:property value="#stu.gender"/></td>
			<td><s:date name="#stu.birthday" format="yyyy年MM月dd日"/></td>
			<td><s:property value="#stu.address"/></td>
			<td><a href="#">删除</a></td>
		</tr>
	</s:iterator>

{ level:2, name:"学生列表", ico:"images/icon_default.gif",link:"students/Students_query.action"},