上一節中，談到了session的工作原理（點選連結到上一節），但實際開發中，使用者可能把cookie禁用了，意味著伺服器向瀏覽器以cookie形式回送session的id號時，瀏覽器不接受這個id，那麼在結賬servlet中就不能再獲取到這個session的id，就會建立一個新的session。
解決：url重寫（點選超連結訪問伺服器時同時傳遞session的id）：
在訪問首頁時就建立session，建立session後，在每一個超連結後面都跟上session的id號，伺服器端得到這個id，獲得伺服器裡的session（getSession方法），那麼就要重寫所有的超連結，就是url重寫。
例：
建立一個servlet:WelcomeServlet作為首頁：

package cn.sun.session;

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;

//網站首頁
 

@WebServlet("/WelcomeSession")
public class WelcomeSession extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public WelcomeSession() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8"
 
);
        response.setContentType("text/html;charset=UTF-8");     
        PrintWriter out=response.getWriter();

        request.getSession(); //建立session

        String url1=response.encodeURL("/day07/SessionDemo1");  //該方法實現url重寫，會自動在這個url地址後面加上session的id號
        String url2=response.encodeURL("/day07/SessionDemo2"); 

        //輸出超連結
        out.print("<a href='"+url1+"'>購買</a>  ");
        out.print("<a href='"+url2+"'>結賬</a>");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
}

SessionDemo1：

package cn.sun.session;

import java.io.IOException;

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

//購買Servlet
@WebServlet("/SessionDemo1")
public class SessionDemo1 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public SessionDemo1() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession(); //得到使用者的session

        //為cookie設定有效期
        String sessionid=session.getId();  //得到session的ID
        Cookie cookie=new Cookie("JSESSIONID",sessionid); //回寫一個與伺服器回寫的cookie同名的cookie，將其覆蓋（就是覆蓋伺服器回寫的cookie）。注：伺服器回寫的session的名稱叫JSESSIONID
        cookie.setPath("/day07");  //設定相同的path將其覆蓋 
        cookie.setMaxAge(30*60);   //設定有效期為30分鐘
        response.addCookie(cookie);  //回寫session

        session.setAttribute("name", "洗衣機"); //儲存使用者購買的物品        
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }

}

SessionDemo2：

package cn.sun.session;

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;
import javax.servlet.http.HttpSession;

//結賬servlet
@WebServlet("/SessionDemo2")
public class SessionDemo2 extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public SessionDemo2() {
        super();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");     
        PrintWriter out=response.getWriter();

        HttpSession session = request.getSession();  //得到來訪者的session
        String product = (String) session.getAttribute("name");  //得到使用者購買的產品

        out.write("您購買的商品是："+product);      
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }

}

執行WelcomeServlet：

點選購買，再點選結賬：