简单购物车

实现的功能:

1.显示所有物品 ShowBookServlet

2.能把选中物品放到购物车中(客户端禁用Cookie的前提下，仍然可以使用) BuyServlet

3.显示购物车，并且有清除所选物品的功能 ShowCartServlet ClearCartServlet

ShowBookServlet.java

BuyServlet.java

 1 import java.io.IOException;
 2 import java.io.PrintWriter;
 3 import java.util.ArrayList;
 4 import java.util.List;
 5 
 6 import javax.servlet.ServletException;
 7 import javax.servlet.http.HttpServlet;
 8 import javax.servlet.http.HttpServletRequest;
 9 import javax.servlet.http.HttpServletResponse;
10 import javax.servlet.http.HttpSession;
11 
12 import com.itheima.domain.Book;
13 import com.itheima.domain.BookDB;
14 
15 /**
16  实现功能：将传送过来的书加入购物车
17  
18  功能分析：
19         1.得到传送过来的参数，通过BookDB得到书
20         2.得到session  不存在则创建并加入  存在则直接加入到ArrayList中
21 */
22 public class BuyServlet extends HttpServlet {
23 
24     public void doGet(HttpServletRequest request, HttpServletResponse response)
25             throws ServletException, IOException {
26         response.setContentType("text/html;charset=UTF-8");
27         PrintWriter out = response.getWriter();
28         
29         //得到要买的书
30         String id = request.getParameter("id");
31         Book book = BookDB.findBookById(id);
32         //向购物车中放书
33         HttpSession session = request.getSession();
34         List<Book> cart = (List<Book>) session.getAttribute("cart");//此处书不止一本且重复用ArrayList集合作为书的所选正合适
35         if(cart==null){
36             cart = new ArrayList<Book>();//第一次购物产生
37             session.setAttribute("cart", cart);
38         }
39         //有购物车  
40         cart.add(book);//作为引用不用刷新
41         String url = request.getContextPath()+"/servlet/ShowBooksServlet";
42         url = response.encodeURL(url);
43         out.write("【"+book.getName()+"】已经放入您的购物车了！<a href='"+url+"'>继续购物</a>");
44     }
45 
46     public void doPost(HttpServletRequest request, HttpServletResponse response)
47             throws ServletException, IOException {
48 
49         doGet(request, response);
50     }
51 
52 }

ClearCartServlet

 1 import java.io.IOException;
 2 import java.io.PrintWriter;
 3 import javax.servlet.ServletException;
 4 import javax.servlet.http.HttpServlet;
 5 import javax.servlet.http.HttpServletRequest;
 6 import javax.servlet.http.HttpServletResponse;
 7 import javax.servlet.http.HttpSession;
 8 //清空购物车，重新购买
 9 public class ClearCartServlet extends HttpServlet {
10 
11     public void doGet(HttpServletRequest request, HttpServletResponse response)
12             throws ServletException, IOException {
13         response.setContentType("text/html;charset=UTF-8");
14         PrintWriter out = response.getWriter();
15         
16         HttpSession session = request.getSession(false);
17         if(session==null){
18             out.write("你都没有购物车，你销个鬼");
19             return;
20         }
21 //        session.invalidate();//太绝   会把全部的session 清空  不适合
22         session.removeAttribute("cart");
23         String url = request.getContextPath()+"/servlet/ShowBooksServlet";
24         url = response.encodeURL(url);
25         out.write("您的购物车清空完毕<br/><a href='"+url+"'>继续购物</a>");
26         
27     }
28 
29     public void doPost(HttpServletRequest request, HttpServletResponse response)
30             throws ServletException, IOException {
31 
32         doGet(request, response);
33     }
34 
35 }

ShowCartServlet

 1 import java.io.IOException;
 2 import java.io.PrintWriter;
 3 import java.util.List;
 4 import javax.servlet.ServletException;
 5 import javax.servlet.http.HttpServlet;
 6 import javax.servlet.http.HttpServletRequest;
 7 import javax.servlet.http.HttpServletResponse;
 8 import javax.servlet.http.HttpSession;
 9 
10 import com.itheima.domain.Book;
11 //显示购物车中的商品
12 public class ShowCartServlet extends HttpServlet {
13 
14     public void doGet(HttpServletRequest request, HttpServletResponse response)
15             throws ServletException, IOException {
16         response.setContentType("text/html;charset=UTF-8");
17         PrintWriter out = response.getWriter();
18         
19         HttpSession session = request.getSession(false);//仅作查看
20         if(session==null){
21             out.write("对不起，您还没有买任何的东东");
22             return;
23         }
24         List<Book> cart = (List<Book>)session.getAttribute("cart");
25         //此处在移除后cart的值为空，若是cart.size()在前 则会出现NullPointerException
26         if(cart==null||cart.size()<1){
27             out.write("对不起，您还没有买任何的东东");
28             return;
29         }
30         String url0 = request.getContextPath()+"/servlet/ClearCartServlet";
31         url0 = response.encodeURL(url0);
32         out.write("您购买的商品如下：<a href='"+url0+"'>清空购物车</a><br/>");
33         for(Book b:cart){
34             out.write(b.getName()+"<br/>");
35         }
36         String url = request.getContextPath()+"/servlet/ShowBooksServlet";
37         url = response.encodeURL(url);
38         out.write("<br/><a href='"+url+"'>继续购物</a>");
39     }
40 
41     public void doPost(HttpServletRequest request, HttpServletResponse response)
42             throws ServletException, IOException {
43 
44         doGet(request, response);
45     }
46 
47 }