Ajax、Json对象及完成添加购物车的功能

痛定思痛。 2022-06-04 07:29 145阅读 0赞

Ajax：Asynchronous JavaScript and XML，其实这并不是一项新的技术，不过是融合了几种技术，实现了异步请求，即不需要刷新页面，用户并不会察觉到有请求的发生，但是实际上浏览器引擎发送了请求，只不过用户不再需要等到服务器的响应才去执行其他操作。  
关键对象：XMLHttpRequest  
关键方法：  
open();发送请求  
send();发送数据  
属性：  
readyState  
status （服务器返回的状态码）  
responseText  
responseXML  
事件：onreadystatechange

JSONObject对象所依赖的jar包：  
![SouthEast][]

package com.itdream.json;
    
    import com.itdream.domain.Book;
    import net.sf.json.JSONArray;
    import net.sf.json.JSONObject;
    import net.sf.json.JsonConfig;
    import org.junit.Test;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /** * Created by Dream on 2017/12/7. */
    public class JsonTest {
        @Test  //使用JSONObject封装数据对象类型数据
        public void test1(){
            Book b = new Book();
            b.setId("123");
            b.setName("Is your light still shinning?");
            b.setPrice(99);
            b.setCategory("启发");
            b.setPnum(15);
            b.setDescription("启发思维");
    
            String s = JSONObject.fromObject(b).toString();
            System.out.println(s);
        }
        //{
       "category":"启发","description":"启发思维","id":"123","name":"Is your light still shinning?","pnum":15,"price":99}
    
        @Test  //使用JSONArray封装List<Book>对象数据类型
        public void test2(){
            List<Book> list = new ArrayList<>();
            Book b1 = new Book();
            b1.setId("123");
            b1.setName("Is your light still shinning?");
            b1.setPrice(99);
            b1.setCategory("启发");
            b1.setPnum(15);
            b1.setDescription("启发思维");
    
            Book b2 = new Book();
            b2.setId("123");
            b2.setName("Is your light still shinning?");
            b2.setPrice(99);
            b2.setCategory("启发");
            b2.setPnum(15);
            b2.setDescription("启发思维");
    
            Book b3 = new Book();
            b3.setId("123");
            b3.setName("Is your light still shinning?");
            b3.setPrice(99);
            b3.setCategory("启发");
            b3.setPnum(15);
            b3.setDescription("启发思维");
    
            list.add(b1);
            list.add(b2);
            list.add(b3);
            String s = JSONArray.fromObject(list).toString();
            System.out.println(s);
        }
        //[{
       "category":"启发","description":"启发思维","id":"123","name":"Is your light still shinning?","pnum":15,"price":99},{
       "category":"启发","description":"启发思维","id":"123","name":"Is your light still shinning?","pnum":15,"price":99},{
       "category":"启发","description":"启发思维","id":"123","name":"Is your light still shinning?","pnum":15,"price":99}]
    
        @Test  //使用JsonConfig去除不要的字段数据
        public void test3(){
            List<Book> list = new ArrayList<>();
            Book b1 = new Book();
            b1.setId("123");
            b1.setName("Is your light still shinning?");
            b1.setPrice(99);
            b1.setCategory("启发");
            b1.setPnum(15);
            b1.setDescription("启发思维");
    
            Book b2 = new Book();
            b2.setId("123");
            b2.setName("Is your light still shinning?");
            b2.setPrice(99);
            b2.setCategory("启发");
            b2.setPnum(15);
            b2.setDescription("启发思维");
    
            Book b3 = new Book();
            b3.setId("123");
            b3.setName("Is your light still shinning?");
            b3.setPrice(99);
            b3.setCategory("启发");
            b3.setPnum(15);
            b3.setDescription("启发思维");
    
            list.add(b1);
            list.add(b2);
            list.add(b3);
            JsonConfig jc = new JsonConfig();
            jc.setExcludes(new String[]{
       "pnum","id","category","description"});
            String s = JSONArray.fromObject(list,jc).toString();
            System.out.println(s);
        }
        //结果：
        //[{
       "name":"Is your light still shinning?","price":99},{
       "name":"Is your light still shinning?","price":99},{
       "name":"Is your light still shinning?","price":99}]
    }

在进行购物的时候，我们将欲购买的商品添加至购物车，购物车应该存放于session对象中  
思路：  
初始化的数据num=1，便于对第一次加入购物车时的数据进行数量赋值  
1.首先获取session对象中的cart数据  
2.如果是第一次添加购物车，那么获取的cart对象则为空，这时我们new一个购物车对象  
3.判断添加的商品是否存在于购物车中，如果存在，则需要将原先存在于购物车中的商品的数量取出并进行+1操作；如果不存在于购物车中，则将初始化的num赋予给对应商品的数量  
4.将商品及其num值添加到cart中  
5.将cart设置到Session域中

public class AddCartServlet extends HttpServlet { 
        public void doGet(HttpServletRequest request,HttpServletResponse response)throws IOException{
            response.setContentType("text/html;charset=utf-8");
            String id = request.getParameter("id");
            BookService bs = new BookService();
            Book book = bs.findBookById(id);
            Map<Book,String> cart = (Map<Book, String>) request.getSession().getAttribute("cart");
            int num = 1; //记录数量
            if(cart == null){  //第一次加购物车，购物车还没放session
                cart = new HashMap<>();
            }
            if(cart.containsKey(book)){  //如果这本书已经存在于购物车，那么则需要取出cart中的value值，+1
                String n = cart.get(book);
                num = Integer.parseInt(n)+1;
            }
            cart.put(book,num+"");
            request.getSession().setAttribute("cart",cart);
            response.getWriter().write("<a href='"+request.getContextPath()+"/servlet/pageServlet'>继续购物</a>，<a href='"+request.getContextPath()+"/cart.jsp'>查看购物车</a>");
        }
        public void doPost(HttpServletRequest request,HttpServletResponse response)throws IOException{
            doGet(request,response);
        }
    }

[SouthEast]: /images/20220604/152fbd1908d046149d6cd87a15beb9a1.png