Session简单实现购物功能

1,IndexServlet.java 主页Servlet实现主页显示商品

    import java.io.IOException;  
    import java.io.PrintWriter;  
    import java.util.LinkedHashMap;  
    import java.util.Map;  
    import java.util.Set;  
    import javax.servlet.ServletException;  
    import javax.servlet.http.HttpServlet;  
    import javax.servlet.http.HttpServletRequest;  
    import javax.servlet.http.HttpServletResponse;  
      
    //首页：列出所有书  
    public class IndexServlet extends HttpServlet {  
      
        public void doGet(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            response.setContentType("text/html;charset=UTF-8");  
            PrintWriter out = response.getWriter();   
            request.getSession();     
            out.write("本网站有如下书：<br/>");     
            Set<Map.Entry<String,Book>> set = DB.getAll().entrySet();  
            for(Map.Entry<String,Book> me : set){  
                Book book = me.getValue();  
                String url = "/day07/servlet/BuyServlet?id=" + book.getId();  
                url = response.encodeURL(url);  
                out.println(book.getName()  + "   <a href='"+url+"'>购买</a><br/>");  
            }     
        }  
      
        public void doPost(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            doGet(request, response);  
        }  
      
    }  

2,BuyServlet.java 该Servlet实现购买页面

    import java.io.IOException;  
    import java.util.ArrayList;  
    import java.util.List;  
    import javax.servlet.ServletException;  
    import javax.servlet.http.HttpServlet;  
    import javax.servlet.http.HttpServletRequest;  
    import javax.servlet.http.HttpServletResponse;  
    import javax.servlet.http.HttpSession;  
    public class BuyServlet extends HttpServlet {  
        public void doGet(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            String id = request.getParameter("id");  
            Book book = (Book) DB.getAll().get(id);  //得到用户想买的书   
            HttpSession session = request.getSession();  
            /*Cookie cookie = new Cookie("JSESSIONID",session.getId()); 
            cookie.setMaxAge(30*60); 
            cookie.setPath("/day07"); 
            response.addCookie(cookie);*/     
            List list = (List) session.getAttribute("list");  //得到用户用于保存所有书的容器  
            if(list==null){  
                list = new ArrayList();  
                session.setAttribute("list", list);  
            }  
            list.add(book);  
            //request.getRequestDispatcher("/servlet/ListCartServlet").forward(request, response);    
            String url = response.encodeRedirectURL("/day07/servlet/ListCartServlet");//重新URL  
            //System.out.println(url);  
            response.sendRedirect(url);   
        }  
        public void doPost(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            doGet(request, response);  
        }  
      
    }  

3，ListCartServlet.java 实现将购买的商品通过Session保存发给ListCartServlet,显示你购买的商品

    import java.io.IOException;  
    import java.io.PrintWriter;  
    import java.util.List;  
    import javax.servlet.ServletException;  
    import javax.servlet.http.HttpServlet;  
    import javax.servlet.http.HttpServletRequest;  
    import javax.servlet.http.HttpServletResponse;  
    import javax.servlet.http.HttpSession;  
    public class ListCartServlet extends HttpServlet {  
      
        public void doGet(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
            response.setContentType("text/html;charset=UTF-8");  
            PrintWriter out = response.getWriter();   
            HttpSession session = request.getSession();  
            List<Book> list = (List) session.getAttribute("list");  
            if(list==null || list.size()==0){  
                out.write("对不起，您还没有购买任何商品!!");  
                return;  
            }     
            //显示用户买过的商品  
            out.write("您买过如下商品:<br>");  
            for(Book book : list){  
                out.write(book.getName() + "<br/>");  
            }         
        }  
        public void doPost(HttpServletRequest request, HttpServletResponse response)  
                throws ServletException, IOException {  
      
            doGet(request, response);  
        }  
      
    }