老师我的代码哪里有问题

来源：2-6 自由编程

慕侠92699508

2020-06-10 11:50:17

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
 <form action="/servlet_advanced/sum">
  <input type="text" name="num" placeholder="请输入100以内的数字">
  <input type="submit" value="求累加和">
 </form>
</body>
</html>

package com.imooc.servlet.direct;
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 SumAll
 */
@WebServlet("/sum")
public class SumCheckServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SumCheckServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
 /**
  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  String num=request.getParameter("num");
  int n=Integer.parseInt(num);
  int sum=0;
  for(int i=1;i<=n;i++) {
   sum+=i;
  }
  request.setAttribute("result", sum);
  request.getRequestDispatcher("/sumindex").forward(request, response);
 }
}

package com.imooc.servlet.direct;
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 SumIndexServlet
 */
@WebServlet("/sumindex")
public class SumIndexServlet extends HttpServlet {
 private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public SumIndexServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
 /**
  * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
  */
 protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
  request.setCharacterEncoding("utf-8");
  response.setCharacterEncoding("utf-8");
  response.setContentType("text/html;charset=utf-8");
     Object sum=request.getAttribute("result");
  response.getWriter().println("计算结果为："+sum);
 }
}

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