查看用户浏览器过的商品--Cookie
ProductDao：list数组模拟数据库，获取数据 Product：model 把数据对象化 Logic：service层 DetailServlet：显示单个商品数据 ListServlet：商品集合显示和显示浏览过的商品。 ProductDao： package dao; import java.util.ArrayList; import java.util.List; import entity.*; public class ProductDao { static List<Product> list=new ArrayList<Product>(); static { for(int i=0;i<10;i++) { Product product=new Product(); product.setNumber(i); product.setName("我是"+i); list.add(product); } } public Product findOne(int id) { for (Product product:list) { if(product.getNumber()==id) { return product; } } return null; } public List<Product> findList(){ return list; } } Product： package entity; public class Product { private int number; public int getNumber() { return number; } public void setNumber(int number) { this.number = number; } public String getName() { return name; } public void setName(String name) { this.name = name; } private String name; } Logic： package service; import java.util.List; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServletRequest; import dao.ProductDao; import entity.Product; public class Logic { public Product findOne(int id) { ProductDao productDao=new ProductDao(); return productDao.findOne(id); } public List<Product> findList(){ ProductDao productDao=new ProductDao(); return productDao.findList(); } } DetailServlet： package servlet; import java.io.IOException; import java.io.PrintWriter; import java.util.Arrays; import java.util.LinkedList; import java.util.List; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import entity.Product; import javafx.print.Collation; import service.*; @WebServlet("/DetailServlet") public class DetailServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); int id=Integer.parseInt(request.getParameter("id")); Logic logic=new Logic(); Product product=logic.findOne(id); String name=product.getName(); PrintWriter printWriter=response.getWriter(); String html=""; html+="<html>"; html+="<body>"; html+="<table border='1' align='center' width='600px'>"; html+="<tr>"; html+="<th>编号</th><th>名字</th>"; html+="</tr>"; if(product!=null) { html+="<tr>"; html+="<td>"+id+"</td>"+"<td>"+name+"</td>"; html+="</tr>"; } html+="</table>"; html+="<center><a href='"+request.getContextPath()+"/ListServlet'>"+"返回列表</a></center>"; html+="</body>"; html+="</html>"; printWriter.write(html); Cookie cookie=new Cookie("lastone", createValue(request, id)); cookie.setMaxAge(100); response.addCookie(cookie); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } //修改接收到的Cookie值 public String createValue(HttpServletRequest request,int id) { String idString=String.valueOf(id); String prodHist=null; Cookie[] cookies=request.getCookies(); if(cookies!=null) { for(Cookie cookie:cookies) { if(cookie.getName().equals("lastone")) { prodHist=cookie.getValue(); break; } } } if(prodHist==null||cookies==null) { return idString; } String[] strings=prodHist.split("#"); List<String> collation=Arrays.asList(strings); LinkedList<String> linkedList=new LinkedList<String>(collation); if(linkedList.size()<3) { if(linkedList.contains(idString)) { linkedList.remove(idString); linkedList.addFirst(idString); }else { linkedList.addFirst(idString); } }else { if(linkedList.contains(idString)) { linkedList.remove(idString); linkedList.addFirst(idString); }else { linkedList.removeLast(); linkedList.addFirst(idString); } } StringBuffer stringBuffer=new StringBuffer(); for(String string:linkedList) { stringBuffer.append(string+"#"); } String result=stringBuffer.toString(); result=result.substring(0, result.length()-1); return result; } } ListServlet： package servlet; import java.io.IOException; import java.io.PrintWriter; import java.util.List; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import entity.Product; import service.Logic; @WebServlet("/ListServlet") public class ListServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); //service层 Logic logic=new Logic(); List<Product> list=logic.findList(); PrintWriter printWriter=response.getWriter(); String html=""; html+="<html>"; html+="<body>"; html+="<table border='1' align='center' width='600px'>"; html+="<tr>"; html+="<th>编号</th><th>名字</th>"; html+="</tr>"; for(Product One:list) { String name=One.getName(); int id=One.getNumber(); html+="<tr>"; html+="<td>"+id+"</td>"+"<td><a href='"+request.getContextPath()+"/DetailServlet?id="+id+"'>"+name+"</a></td>"; html+="</tr>"; } html+="</table>"; String value=null; Cookie[] cookies= request.getCookies(); if(cookies!=null) { for(Cookie cookie:cookies) { if(cookie.getName().equals("lastone")) { value=cookie.getValue(); break; } } String[] strings=value.split("#"); for(String number:strings) { Product product=logic.findOne(Integer.parseInt(number)); html+=product.getNumber()+" "+product.getName()+"<br/>"; } } html+="</body>"; html+="</html>"; printWriter.write(html); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } } 难点：如何保留浏览过的商品？ 生成cookie的值 分析： 当前cookie值 传入商品id 最终cookie值 null或没有prodHist 1 1 （算法： 直接返回传入的id ） 1 2 2,1 （没有重复且小于3个。算法：直接把传入的id放最前面 ） 2,1 1 1,2（有重复且小于3个。算法：去除重复id，把传入的id放最前面 ） 3,2,1 2 2,3,1（有重复且3个。算法：去除重复id，把传入的id放最前面） 3,2,1 4 4,3,2（没有重复且3个。算法：去最后的id，把传入的id放最前面）
