增加购物车功能

这个实例没用到数据库，用的map集合

 Book

package com.itheima.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 + "]";
}



}

DBUtil

package com.itheima.util;

import java.util.HashMap;
import java.util.Map;

import com.itheima.entity.Book;

public class DBUtil {
  static Map<String,Book>books=new HashMap<String ,Book>();
  static {
    books.put("1",new Book("1", "金瓶梅", 20, "王润鑫"));
    books.put("2",new Book("2", "葵花宝典", 20, "杨成毅"));
    books.put("3",new Book("3", "九阴真经", 30, "陈光"));
    books.put("4",new Book("4", "玉女心经", 10, "陈志家"));

  }
  //得到所有书
  public static Map<String ,Book> findAllBook(){

  return books;
  }
  /**
   * 
   * 根据id查找指定的书
   * */
  public static Book findBookById(String id){

  return books.get(id);  
  }




}

AddCart

package com.itheima.cart;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import javax.jms.Session;
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 {
//把界面ShowAllBooksServlet要添加购物车的书放到这里    
    private Map<String, Book> findAllBook;
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        //根据id得到书
        String id =request.getParameter("id");
        Book book = DBUtil.findBookById(id);
        //得到session对象
        HttpSession seesion=request.getSession();
        //从session中取到list(购物车)

        List<Book> list=(List<Book>)seesion.getAttribute("cart");//刚开始购物车是没有东西的,这个cart的session域也是没有创建的
        if (list==null) {
            list=new ArrayList<Book>();//数组为空，new一个数组
        }
        list.add(book);//根据id获得书放到数组里；
        seesion.setAttribute("cart", list);//把list放回到session域中

        PrintWriter out = response.getWriter();
        out.print("购买成功，2秒调回到商品列表界面");
        response.setHeader("refresh", "2;url=ShowAllBooksServlet");

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    doGet(request, response);


    }

}

ShowCart

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 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/>");
     //得到session对象

  List<Book>books=(List<Book>)request.getSession().getAttribute("cart") ;
  if (books==null) {
    out.print("你还什么都没呢");
    response.setHeader("refresh", "2;url=ShowAllBooksServlet");
     return;//这里不加return 会有错误。还会向下执行，那么book里面没东西，就会出现异常；
  }
   for (Book book : books) {
    out.print(book.getName()+"<br/>");
  }

  }

  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

     doGet(request, response);
  }

}

RemoveCar

package com.itheima.cart;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class RemoveCar extends HttpServlet {


  public void doGet(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    response.setContentType("text/html;charset=utf-8");
    request.getSession().removeAttribute("cart"); 
    PrintWriter out = response.getWriter();
    out.print("购物车清楚成功，2秒后,返回商品列表首页");
    response.setHeader("refresh", "2;url=ShowAllBooksServlet");

  }


  public void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {
         doGet(request, response);
  }

}