jsp页面重定向到另外一个jsp页面时，重定向后如何获取到servlet的数据(已连接数据库)？

private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
    doPost(req, res);
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
    res.setCharacterEncoding("utf-8");//处理响应乱码
    PrintWriter out = res.getWriter();// 打印输出流
    //通过req.getParamater方法从网页中获取输入的信息
    String name = req.getParameter("name");// 根据参数名称获取参数值
    String sex = req.getParameter("sex");
    String age =req.getParameter("age");
    Integer age1 = null;
    if (age!=null && !age.equals("")) {
        age1 = Integer.parseInt(req.getParameter("age"));
    }
            String grade = req.getParameter("grade");
    String opt = req.getParameter("opt");
    String th =req.getParameter("th");
      if ("0".equals(opt)) {
          try {
            //查询
                List<Teacher> teacher = new TeacherDAO().selectTeacher(name, sex, grade);
                req.setAttribute("teacher", teacher);
                req.getRequestDispatcher("/page/teacher.jsp").forward(req, res);
                req.getRequestDispatcher("/page/select_teacher.jsp").forward(req, res);    
            //    res.sendRedirect("/page/teacher.jsp");    
            } catch (Exception e) {
                List<Teacher> teacher = new TeacherDAO().selectTeacher(name, sex, grade);
                req.setAttribute("teacher", teacher);
                req.getRequestDispatcher("/page/select_teacher.jsp").forward(req, res);
            }
     } else {
        req.getRequestDispatcher("/page/teacher.jsp").forward(req, res);
    } 
}

<%-- <%=((List)request.getAttribute("teacher")).size() %> --%> <% List list = (List) request.getAttribute("teacher");

        if (list != null) {
            for (Teacher e : list) {
    %>
    <tr>
        <td><%=e.getName()%></td>
        <td><%=e.getSex()%></td>
        <td><%=e.getGrade()%></td>
    <%--     <td><%=e.getAge()%></td> --%>
    </tr>
    <%
        }
        }
    %>
    
    <form id="th" action="teacher" method="post">
    <input type="text" id="opt" name="opt" style="display: none">
    <!-- <input type="hidden" id="opt" name="opt" > -->
    <p>
        名字: <input type="text" name="name">
    </p>
    <p>
        性别: <input type="text" name="sex">
    </p>
    <p>
        年龄: <input type="text" name="age">
    </p>
    <p>
        年级: <input type="text" name="grade">
    </p>
    <p>
        <input type="button" id="opt" value="查询" onclick="query();">
          <input type="button"value="添加" onclick="add();">
            <input type="button" value="修改" onclick="update();">
              <input type="button" value="删除" onclick="delete1();">
    </p>
    
</form>        
</table>

<%-- <%=((List)request.getAttribute("teacher")).size() %> --%>

姓名

性别

年级

<% List list = (List) request.getAttribute("teacher");

        if (list != null) {
            for (Teacher e : list) {
    %>
    <tr>
        <td><%=e.getName()%></td>
        <td><%=e.getSex()%></td>
        <td><%=e.getGrade()%></td>
    <%--     <td><%=e.getAge()%></td> --%>
    </tr>
    <%
        }
        }
    %>
    <form id="th" action="teacher" method="post">
    <input type="text" id="opt" name="opt" style="display: none">
    <!-- <input type="hidden" id="opt" name="opt" > -->

    <p>
        <input type="button" id="opt" value="查询" onclick="query();">
    </p>
</form>        
</table>

姓名

性别

年级

从作用域中取 放在session或者application

将你需要的数据放入session中，重定向后去这个session拿