public boolean delete(Course n) {

    boolean f=false;

    int a=0;

    String sql="delete from submitcourse where teachername=?";//通过老师姓名来删除

    try {

         Connection conn=DBUtil.getConnection();

         PreparedStatement pstmt=conn.prepareStatement(sql);

         pstmt.setString(1,n.getTeachername());

          a=pstmt.executeUpdate();

          System.out.println("fuck you");

    } catch (SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

    if(a>0) f=true;

    return f;

}

package servlet;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import Bean.Course;

import dao.daoCourse;

/**

 * Servlet implementation class course_servlet

 */

@WebServlet("/course_servlet")

public class course_servlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

       daoCourse gooddao=new daoCourse();

    /**

     * @see HttpServlet#HttpServlet()

     */

    public course_servlet() {

        super();

        // TODO Auto-generated constructor stub

    }

    /**

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

     */

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

        // TODO Auto-generated method stub

        doPost(request, response);

    }

    /**

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

     */

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

        // TODO Auto-generated method stub

        request.setCharacterEncoding("utf-8");

        response.setCharacterEncoding("utf-8");

        String method=request.getParameter("method");

        if("add".equals(method))

        {

        String teachername=request.getParameter("teachername");

        String classname=request.getParameter("classname");

        String place=request.getParameter("place");

        Course n=new Course(classname,teachername,place);

        gooddao.add(n);

        request.setAttribute("message", "添加成功");

        request.getRequestDispatcher("NewFile2.jsp").forward(request, response);

        }

        else if("delete".equals(method)) {

            String teachername=request.getParameter("teachername");

            Course n=new Course();

            n.setTeachername(teachername);

            gooddao.delete(n);

            request.setAttribute("message", "删除成功");

            request.getRequestDispatcher("course_servlet?method=looklist").forward(request, response);

        }

        else if("looklist".equals(method)) {

            List<Course> nt= gooddao.list();

            request.setAttribute("nt", nt);

            System.out.println("王建民");

            request.getRequestDispatcher("NewFile3.jsp").forward(request, response);

        }

    }

}