package com.imooc.servlet;

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

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

public class TestServlet extends HttpServlet{

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String n = request.getParameter("n");
        int sum = 0;
        int m = Integer.parseInt(n);
        for(int i = 1 ;i <= m;i++) {
            sum = sum + i;
        }
        PrintWriter out = response.getWriter();//向浏览器输出的数据流
        out.println(sum);
    }
    
}

=========================================

  <servlet>
  <servlet-name>test</servlet-name>
  <servlet-class>com.imooc.servlet.TestServlet</servlet-class>
  </servlet>
 
  <servlet-mapping>
  <servlet-name>test</servlet-name>
  <url-pattern>/test</url-pattern>
  </servlet-mapping>