JavaWeb学习-会话管理系列-8-Session练习-模拟购物车实现过程

野性酷女 2022-01-29 07:59 247阅读 0赞

前面学习cookie的时候，做了一个模拟浏览历史纪录的练习，这篇学习session，我们来再前面知识基础上，做一个模拟购物车的场景。前面文章中Book.java和DBUtil.java都需要拿过来使用。

**1.文件结构**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1NDE5NDY_size_16_color_FFFFFF_t_70][]

ShowAllBooksServlet.java是显示全部商品列表页面，提供点击一本书，点击效果就是模拟添加购物车功能。AddCart.java就是处理添加购物车逻辑，showCart.java就是显示购物页面。

**2.文件代码**

web.xml

<?xml version="1.0" encoding="UTF-8"?>
    <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
      <display-name>SessionDemo</display-name>
      
    
      <servlet>
        <servlet-name>showAllBooksServlet</servlet-name>
        <servlet-class>com.anthony.cart.ShowAllBooksServlet</servlet-class>
      </servlet>
      <servlet-mapping>
        <servlet-name>showAllBooksServlet</servlet-name>
        <url-pattern>/showAllBook</url-pattern>
      </servlet-mapping>
      
      <servlet>
        <servlet-name>addCart</servlet-name>
        <servlet-class>com.anthony.cart.AddCart</servlet-class>
      </servlet>
      <servlet-mapping>
        <servlet-name>addCart</servlet-name>
        <url-pattern>/addCart</url-pattern>
      </servlet-mapping>
      
      <servlet>
        <servlet-name>showCart</servlet-name>
        <servlet-class>com.anthony.cart.ShowCart</servlet-class>
      </servlet>
      <servlet-mapping>
        <servlet-name>showCart</servlet-name>
        <url-pattern>/showCart</url-pattern>
      </servlet-mapping>
      <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
      </welcome-file-list>
    </web-app>

DBUtil.java

package com.anthony.util;
     
    import java.util.HashMap;
    import java.util.Map;
     
    import com.anthony.entity.Book;
     
    public class DBUtil {
    	
    	private static Map<String, Book> books = new HashMap<String, Book>();
    	
    	//这里不走数据库查询，直接生成几本书来模拟下
    	static {
    		books.put("1", new Book("1", "西游记", 16.9, "吴承恩"));
    		books.put("2", new Book("2", "红楼梦", 37.3, "曹雪芹"));
    		books.put("3", new Book("3", "三国演义", 25.8, "罗贯中"));
    		books.put("4", new Book("4", "水浒传", 33.0, "施耐庵"));
    	}
    	
    	//得到所有图书
    	public static Map<String, Book> findAllBooks() {
    		return books;
    	}	
    	
    	//根据id查找到书
    	public static Book findBookById(String id) {
    		return books.get(id);
    	}
    }

Book.java

package com.anthony.entity;
     
    public class Book {
    	private String id;
    	private String name;
    	private double price;
    	private String author;
    	
    	public Book(String id, String name, double price, String author) {
    		super();
    		this.id = id;
    		this.name = name;
    		this.price = price;
    		this.author = author;
    	}
    	public String getId() {
    		return id;
    	}
    	public void setId(String id) {
    		this.id = id;
    	}
    	public String getName() {
    		return name;
    	}
    	public void setName(String name) {
    		this.name = name;
    	}
    	public double getPrice() {
    		return price;
    	}
    	public void setPrice(double price) {
    		this.price = price;
    	}
    	public String getAuthor() {
    		return author;
    	}
    	public void setAuthor(String author) {
    		this.author = author;
    	}
    	@Override
    	public String toString() {
    		return "Book [id=" + id + ", name=" + name + ", price=" + price + ", author=" + author + "]";
    	}
    	
    }

ShowAllBooksServlet.java

package com.anthony.cart;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.Map;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    import com.anthony.entity.Book;
    import com.anthony.util.DBUtil;
    
    public class ShowAllBooksServlet extends HttpServlet {
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		resp.setContentType("text/html;charset=UTF-8");
    		PrintWriter out = resp.getWriter();
    		
    		//显示本网站全部商品列表
    		out.print("本网站有以下好书：<br/>");
    		Map<String, Book> books = DBUtil.findAllBooks();
    		for (Map.Entry<String, Book> b : books.entrySet()) {
    			out.print("<a href='"+req.getContextPath()+"/addCart?id="+b.getKey()+"' target='_blank'</a>"+b.getValue().getName()+"</br>");
    		}
    		
    		//点击查看购物车
    		out.print("<a href='"+req.getContextPath()+"/showCart' target='_blank'>查看购物车</a><br/>");
    		
    	}
    
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req, resp);
    	}
    	
    	
    }

AddCart.java

package com.anthony.cart;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    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;
    
    import com.anthony.entity.Book;
    import com.anthony.util.DBUtil;
    
    public class AddCart extends HttpServlet {
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		resp.setContentType("text/html;charset=UTF-8");
    		PrintWriter out = resp.getWriter();
    		//根据id得到书
    		String id = req.getParameter("id");
    		Book book = DBUtil.findBookById(id);
    		
    		//从session中取出list(购物车)
    		HttpSession ss = req.getSession();
    		List<Book> list = (List<Book>) ss.getAttribute("cart");
    		//判断list为空
    		if(list == null) {
    			list = new ArrayList<Book>();
    		}
    		list.add(book);
    		out.print("购买成功！");
    		//把cart添加到session
    		ss.setAttribute("cart", list);
    	}
    
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req, resp);
    	}
    	
    	
    }

ShowCart.java

package com.anthony.cart;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    import java.util.ArrayList;
    import java.util.Iterator;
    import java.util.List;
    import java.util.Map;
    
    import javax.servlet.ServletException;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import javax.servlet.http.HttpSession;
    
    import com.anthony.entity.Book;
    import com.anthony.util.DBUtil;
    
    public class ShowCart extends HttpServlet {
    
    	@Override
    	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		resp.setContentType("text/html;charset=UTF-8");
    		PrintWriter out = resp.getWriter();
    		//得到session对象
    		List<Book> list = (List<Book>) req.getSession().getAttribute("cart");
    		//遍历list
    		if(list == null) {
    			list = new ArrayList<Book>();
    			out.print("您目前还添加商品到购物车!");
    			//重定向到商品页面
    			resp.setHeader("refresh", "2;url="+req.getContextPath()+"/showAllBook");
    			return;
    		}
    		for (Book book : list) {
    			out.print(book.getName() + "<br/>");
    		}
    	}
    
    	@Override
    	protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    		doGet(req, resp);
    	}
    	
    	
    }

**3.测试**

浏览器打开[http://localhost:8080/SessionDemo/showAllBook][http_localhost_8080_SessionDemo_showAllBook]

![20190521150459779.png][]

点击一本书名，相当于点击加入购物车操作。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1NDE5NDY_size_16_color_FFFFFF_t_70 1][]

返回showAllBooks页面，点击查看购物车

![20190521150622502.png][]

如果第一次没有点击直接看购物车，会打印没有添加商品，2秒后重定向到showAllBooks页面。

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1NDE5NDY_size_16_color_FFFFFF_t_70]: /images/20220129/1fabd982ea944432bb283e0bf780e9d9.png
[http_localhost_8080_SessionDemo_showAllBook]: http://localhost:8080/SessionDemo/showAllBook
[20190521150459779.png]: /images/20220129/6ef02673e2614ddda96554d108ef5092.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3UwMTE1NDE5NDY_size_16_color_FFFFFF_t_70 1]: /images/20220129/4533e5e3eaad48cd813ad4d0f5accbe4.png
[20190521150622502.png]: /images/20220129/d6e6c0d4311e48399b748694cf40733f.png