session实现购物车操作

1.新建一个entity实体包，里面存放Book的信息

Book.java里的内容：

package com.itheima.entity;import java.io.Serializable;public class Book implements Serializable{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;}@Overridepublic String toString() {return "Book [id=" + id + ", name=" + name + ", price=" + price+ ", author=" + author + "]";}}

2.新建一个util包，关联数据库，这里没有关联数据库，直接引入本地的书籍

DBUtil.java内容：

package com.itheima.util;import java.util.HashMap;import java.util.Map;import com.itheima.entity.Book;public class DBUtil {private static Map<String, Book> books = new HashMap<String, Book>();static{books.put("1", new Book("1", "谁动了我的奶酪", 20, "斯宾塞·约翰逊"));books.put("2", new Book("2", "唤醒心中的巨人", 20, "安东尼·罗宾斯"));books.put("3", new Book("3", "做最好的自己", 30, "李开复"));books.put("4", new Book("4", "时间简史", 10, "霍金"));}//�õ�������public static Map<String, Book> findAllBooks(){return books;}/** * ���id����ָ������ * @param id * @return */public static Book findBookById(String id){return books.get(id);}}

3.新建购物车包，包含展现所有图书信息，添加图书，和查看购物车三个操作

（1）ShowAllBooksServlet.java

package com.itheima.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.itheima.entity.Book;import com.itheima.util.DBUtil;public class ShowAllBooksServlet 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.print("本网站有以下好书<br/>");Map<String, Book> books = DBUtil.findAllBooks();for (Map.Entry<String, Book> book : books.entrySet()) {String url = request.getContextPath()+"/servlet/addCart?id="+book.getKey();out.print("<a href='"+response.encodeURL(url)+"' >"+book.getValue().getName()+"</a><br/>");}String url2 = request.getContextPath()+"/servlet/showCart";out.print("<a href='"+response.encodeURL(url2)+"'>查看购物车</a>");}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

(2)AddCart.java

package com.itheima.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.itheima.entity.Book;import com.itheima.util.DBUtil;public class AddCart extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=UTF-8");PrintWriter out = response.getWriter();//根据id得到书String id = request.getParameter("id");Book book = DBUtil.findBookById(id);//得到session对象 HttpSession session = request.getSession();//从session中取出list(购物车)List<Book> list = (List<Book>)session.getAttribute("cart");if(list==null){list = new ArrayList<Book>();}list.add(book);session.setAttribute("cart", list);//把list放回session域中out.print("购物成功");String url = request.getContextPath()+"/servlet/showAllBooksServlet";//response.setHeader("refresh", "2;url="+response.encodeURL(url));}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

(3)ShowCart.java

package com.itheima.cart;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;import com.itheima.entity.Book;public class ShowCart extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=UTF-8");PrintWriter out = response.getWriter();out.print("购物车有以下商品:<br/>"); HttpSession session = request.getSession();//得打session对象List<Book> books = (List<Book>)session.getAttribute("cart");if(books==null){out.print("你还什么都没买呢");response.setHeader("refresh", "2;url="+request.getContextPath()+"/servlet/showAllBooksServlet");//response.sendRedirect(request.getContextPath()+"/servlet/showAllBooksServlet");return;}for (Book book : books) {out.write(book.getName()+"<br/>");}//session.setMaxInactiveInterval(10);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}