1.原理图(简图)

    

2.代码

  设置session

import javax.servlet.http.*;

import javax.servlet.*;

import java.io.*;

public class setSession extends HttpServlet{

 public  void doGet(HttpServletRequest req,

                     HttpServletResponse resp)

              throws ServletException,

                      IOException{

           HttpSession session=req.getSession();//返回与当前request相关联的session，如果没有则在服务器端创建一个;

           session.setAttribute("username","zhangjie");

          

                   resp.getWriter().println("------setSession() is ok--------");

          }

}

获取session：

import javax.servlet.http.*;

import javax.servlet.*;

import java.io.*;

public class getSession extends HttpServlet{

 public  void doGet(HttpServletRequest req,

                     HttpServletResponse resp)

              throws ServletException,

                      IOException{

           HttpSession session=req.getSession();//返回与当前request相关联的session，如果没有则在服务器端创建一个;

           resp.getWriter().println(session.getAttribute("username"));

          

                   resp.getWriter().println("------getSession() is ok--------");

          }

}