session完成简单购物功能

原理：

项目目录：

Book.java代码：

package com.haidi8.book;

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;
	}
	@Override
	public String toString() {
		return "Book [id=" + id + ", name=" + name + ", price=" + price
				+ ", author=" + author + "]";
	}
	
	
}

 showallbooksservlet.java代码：

package com.haidi8.car;

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.haidi8.book.Book;
import com.haidi8.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();
		out.print("本网站有一下好书<br/>");
		Map<String, Book> books = DBUtil.findAllBooks();
		for (Map.Entry<String, Book> book : books.entrySet()) {
			String url = request.getContextPath()+"/addcar?id="+book.getKey();
			out.print("<a href='"+response.encodeURL(url)+"' >"+book.getValue().getName()+"</a><br/>");
		}
		String url2 = request.getContextPath()+"/showcar";
		out.print("<a href='"+response.encodeURL(url2)+"'>查看购物车</a>");
	
	}

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

		
	}

}

addcar.java代码：

package com.haidi8.car;

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.haidi8.book.Book;
import com.haidi8.util.DBUtil;

public class addcar 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("car");
		if(list==null){
			list=new ArrayList<Book>();
			
		}
		list.add(book);
		out.print("购买成功！");
		String url = request.getContextPath()+"/showallbooksservlet";
		response.setHeader("refresh", "2;url="+response.encodeURL(url));
		session.setAttribute("car", list);//把list放回session域中
		
		
		

		
	}

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

		
	}

}

showcar.java:

package com.haidi8.car;

import java.io.IOException;
import java.io.PrintWriter;
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 com.haidi8.book.Book;

public class showcar 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("购物车中有一下商品");
		//得到session对象
		List<Book> books = (List<Book>) request.getSession().getAttribute("car");
		if(books==null){
			out.print("你还没有忘购物车中添加商品");
			response.setHeader("refresh", "2;url="+request.getContextPath()+"/showallbooksservlet");
			
			
			//response.sendRedirect(request.getContextPath()+"/showallbooksservlet");
		}
		for(Book book:books){
			out.write(book.getName()+"<br/>");
			
		}

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

	}

}

DBUtil.java代码：

package com.haidi8.util;

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

import com.haidi8.book.Book;


public class DBUtil {
	private static Map<String, Book> books = new HashMap<String, Book>();
	
	static{
		books.put("1", new Book("1", "金瓶梅", 20, "王瑞鑫"));
		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> findAllBooks(){
		return books;
	}
	
	/**
	 * 根据id查找指定的书
	 * @param id
	 * @return
	 */
	public static Book findBookById(String id){
		return books.get(id);
	}
}

web.xml代码:

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
	xmlns="http://java.sun.com/xml/ns/javaee" 
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name>
  
  <servlet>
    <servlet-name>showallbooksservlet</servlet-name>
    <servlet-class>com.haidi8.car.showallbooksservlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>addcar</servlet-name>
    <servlet-class>com.haidi8.car.addcar</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>showcar</servlet-name>
    <servlet-class>com.haidi8.car.showcar</servlet-class>
  </servlet>





  <servlet-mapping>
    <servlet-name>showallbooksservlet</servlet-name>
    <url-pattern>/showallbooksservlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>addcar</servlet-name>
    <url-pattern>/addcar</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>showcar</servlet-name>
    <url-pattern>/showcar</url-pattern>
  </servlet-mapping>	
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

运行效果：