这段代码报错是什么情况？

package com.imooc.el;

public class Student {

private String name;

private String mobile;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getMobile() {

return mobile;

}

public void setMobile(String mobile) {

this.mobile = mobile;

}

}

package com.imooc.el;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class StudentServlet

 */

@WebServlet("/info")

public class StudentServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

    /**

     * @see HttpServlet#HttpServlet()

     */

    public StudentServlet() {

        super();

        // TODO Auto-generated constructor stub

    }

/**

* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

*/

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

Student stu=new Student();

        stu.setName("小明");

        stu.setMobile(null);

        String grade="A";

        request.setAttribute("student", stu);

        request.setAttribute("grade", grade);

        request.getRequestDispatcher("/info.jsp").forward(request, response);

}

}