了request.setAttribute（ “姓名”，名字）;项目在第二次运行时不起作用

Question

我正在制作一个关于在线测试的项目。 当我第一次运行该项目时，它可以正常工作，但是在第二次运行我的项目时，控件不会从我的servlet页面传输到JSP页面。

我认为requset.setAttribute(" ","");无效。

我还尝试重置request，resetBuffer。

 ServletTest2.java

 public class ServletTest2 extends HttpServlet {

ArrayList sno=new ArrayList();
ArrayList question=new ArrayList();
ArrayList cans=new ArrayList();
ArrayList op1=new ArrayList();
ArrayList op2=new ArrayList();
ArrayList op3=new ArrayList();
ResultSet rs;
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {
        out.println("in ServletTest");


        try{ 
            sno.clear();
            question.clear();
            cans.clear();
            op1.clear();
            op2.clear();
            op3.clear();


            System.out.println("in process request");
         stmt=con.prepareStatement("select * from question order by rand() limit 3");
        // stmt.setInt(1,i);
         rs= stmt.executeQuery();

         while(rs.next())
         {


             sno.add(rs.getInt(1));
             question.add(rs.getString(2));
             cans.add(rs.getString(3));
             op1.add(rs.getString(4));
             op2.add(rs.getString(5));
             op3.add(rs.getString(6));
             //System.out.println(question);

         }



          System.out.println(request);
         sendToJsp(request,response);  // User-define method which send value to JSP page
        }

        catch(Exception e){ }
    }
}
static int i;
int ans;
public void sendToJsp(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException 
{      System.out.println("Before request Attribute");

        request.setAttribute("sno", sno.get(i).toString());
        request.setAttribute("question", question.get(i).toString());
         request.setAttribute("cans", cans.get(i).toString());
         request.setAttribute("op1", op1.get(i).toString());
         request.setAttribute("op2", op2.get(i).toString());
         request.setAttribute("op3", op3.get(i).toString());
          System.out.println("After request Attribute");
       // response.flushBuffer();
          //request.getServletContext().getRequestDispatcher("/hello.jsp");
         RequestDispatcher rd=getServletContext().getRequestDispatcher("/dataTest3.jsp");
         rd.forward(request, response);


}
int marks;
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    try{
    System.out.println("In GET Method");
    String answer=request.getParameter("option");
    if(cans.get(i).equals(answer))
    {
        System.out.println("yes ,,,, Get it");
        marks+=10;
    }
    else
    {
        marks-=10;
    }

    /*n++; System.out.println("n : "+n);
    if(n==5)
    { 
        request.setAttribute("marks",""+marks);
        RequestDispatcher rd=request.getRequestDispatcher("/finalSubmit.jsp");
        rd.forward(request, response);
    }*/

    //System.out.println("no of rows : "+(k+1));
    System.out.println("Marks : "+marks);
    i++;
    if(i==sno.size())
    {
        //rs.close();
        //stmt.close(); 
       //
       // stmt1.close();
        System.out.println("in close");
        con.close();
        request.setAttribute("marks",""+marks);
         RequestDispatcher rd=request.getRequestDispatcher("/finalSubmit.jsp");
         rd.forward(request, response);
    }
    sendToJsp(request,response);
    //System.out.println(answer);
    //processRequest(request, response);

    }catch(Exception e){  }
}
static int k,n=0;
String Canswer[]=new String[10];
Connection con=null;
PreparedStatement stmt=null;
Statement stmt1=null;
@Override

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
      try{ System.out.println("In POST Method");
         Class.forName("com.mysql.jdbc.Driver");
         con=(Connection)DriverManager.getConnection("jdbc:mysql://localhost:3306/student","root","");




          processRequest(request, response);
         }catch(Exception e){ }




     }



 }