无法达到预期效果

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<form action="/myjsp/sum" method="get">
		<input type="text" name="number" 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;

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 display
 */
@WebServlet("/display")
public class display extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public display() {
        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
		response.getWriter().append("Served at: ").append(request.getContextPath());
	}

}

package com.imooc.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/sum")
public class sum extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		String number = request.getParameter("number");
		int n = Integer.parseInt(number);
		int sumall=0;
		for (int i = 0; i <= n; i++) {
			sumall=i+sumall;
		}
		PrintWriter out=response.getWriter();
		// 请求转发
		request.setAttribute("sum", sumall);
		request.getRequestDispatcher("/display").forward(request, response);
	}

}

提交之后显示这个

周鸿宁 2020-02-05

源自：Servlet与JSP进阶 3-4 Session的实现原理