Session用法案例 -->实现简单购物车功能(实际项目可能不会这么使用)

07120170909

1、session是在cookie的基础之上，利用cookie返回JSESSIONID(key[服务器随机生成])存在客户端实现，正真的数据存在服务端[key-value]。

2、session的使用步骤：

1)、设置：request.getSession().setAttribute("username", username);

2)、获取：request.getSession(false).getAttribute(username); 注：[false表示沿用之前设置的；不设置，默认为true，如果存在session，则沿用之前的，没有则新建];

3、session是每个浏览器对应一个JSESSIONID;   --->注：例如设置session之后，在Resquest Headers 会存在Cookie:JSESSIONID=A75D52D01876F3B404B8CC668BC8180C

4、代码如下：

package com.tiger.two0906.bean;import java.io.*;import java.util.*;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.*;/** * 水果保存到购物车 * @author tiger * @time 2017年9月9日 */@WebServlet("/fruitSave")public class FruitSave extends HttpServlet {private static final long serialVersionUID = 1L;           public FruitSave() { }protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {List fruit_list = (List) request.getServletContext().getAttribute("fruit_list");String[] ids = request.getParameterValues("sg");List fruits = new ArrayList<>();for (Fruit fruit : fruit_list) {Integer id = fruit.getId();for (String d : ids) {if (id==Integer.parseInt(d)) {fruits.add(fruit);}}}//将信息添加到session中，不同的客户拥有不同的水果列表request.getSession().setAttribute("fruits", fruits);response.sendRedirect("shopCar");}protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}package com.tiger.two0906.bean;import java.io.*;import java.util.*;import javax.servlet.*;import javax.servlet.annotation.WebServlet;import javax.servlet.http.*;@WebServlet("/shopCar")public class FruitCar extends HttpServlet {private static final long serialVersionUID = 1L;protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8");response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");List fruits =  (List) request.getSession().getAttribute("fruits");PrintWriter out = response.getWriter();out.println("");out.println("");out.println("");out.println("");out.println("");out.println("");for (Fruit fruit : fruits) {out.println( ""+ ""+fruit.getId()+""+ ""+fruit.getName()+""+ ""+fruit.getPrice()+""+ ""+fruit.getCount() +""+ "");}out.println("");out.println("");out.println("");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);}}package com.tiger.two0906.bean;/** * 水果bean * @author tiger * @time 2017年9月6日 */public class Fruit {Integer id;String name;double price;int count;public void setId(Integer id) {this.id = id;}public Integer getId() {return 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 int getCount() {return count;}public void setCount(int count) {this.count = count;}public Fruit() { }public Fruit(Integer id, String name, double price, int count) {super();this.id = id;this.name = name;this.price = price;this.count = count;}@Overridepublic String toString() {return "Fruits [id=" + id + ", name=" + name + ", price=" + price + ", count=" + count + "]";}}package com.tiger.two0906.bean;import java.io.*;import java.util.*;import javax.servlet.*;import javax.servlet.annotation.WebServlet;import javax.servlet.http.*;/** * 07120170909 * 水果列表 * @author tiger * @time 2017年9月6日 */@WebServlet("/shopList")public class FruitList extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8");response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");//数据源Fruit[] fruits = {new Fruit(1,"苹果",2.32, 22),new Fruit(2,"雪梨",2.32, 22),new Fruit(3,"坚果",2.32, 22),new Fruit(4,"苹果",2.32, 22),new Fruit(5,"葡萄",2.32, 22)};//将数据源添加进List集合List fruit_list = new ArrayList();Collections.addAll(fruit_list, fruits);request.getServletContext().setAttribute("fruit_list", fruit_list);PrintWriter out = response.getWriter();out.println("");out.println("");out.println("");out.println("");out.println("");out.println("
");out.println("");out.println("");out.println("选择");out.println("水果名");out.println("价格");out.println("数量");out.println("");for (Fruit fruit : fruit_list) {out.println( ""+ ""+fruit.getName()+""+ ""+fruit.getPrice()+""+ ""+fruit.getCount() +"" );}out.println("");out.println("");out.println("");out.println("");out.println("");out.println("");out.println("");out.println("");}@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {doPost(req, resp);}}