实体类
package entity; public class Product { private String id; private String proName; private String proType; private double price; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getProName() { return proName; } public void setProName(String proName) { this.proName = proName; } public String getProType() { return proType; } public void setProType(String proType) { this.proType = proType; } public double getPrice() { return price; } public void setPrice(double price) { this.price = price; } public Product(String id, String proName, String proType, double price) { super(); this.id = id; this.proName = proName; this.proType = proType; this.price = price; } public Product() { super(); // TODO Auto-generated constructor stub } @Override public String toString() { return "Product [id=" + id + ", price=" + price + ", proName=" + proName + ", proType=" + proType + "]"; } }
商品列表servlet
package servlet; import java.io.IOException; import java.io.PrintWriter; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import dao.ProductDao; import entity.Product; /* * 查询所有商品的servlet */ public class ListServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html; charset=utf-8"); ProductDao dao = new ProductDao(); List<Product> list = dao.findAll(); //2.把商品显示到浏览器 PrintWriter writer = response.getWriter(); String html = ""; html += "<html>"; html += "<head>"; html += "<title>显示商品列表</title>"; html += "</head>"; html += "<body>"; html += "<table border='1' align='center' width='600px'>"; html += "<tr>"; html += "<th>编号</th><th>商品名称</th><th>商品型号</th><th>商品价格</th>"; html += "</tr>"; //遍历商品 if (list != null) { for(Product p : list) { html += "<tr>"; html += "<td>"+p.getId()+"</td>" + "<td><a href='"+request.getContextPath()+"/DetailServlet?id="+p.getId()+"'>" +p.getProName()+"</a></td><td>"+p.getProType()+"</td><td>"+p.getPrice()+"</td>"; html += "<tr>"; } } html += "</table>"; /** * 显示浏览过的商品 */ html += "最近浏览过的商品：<br/>"; Cookie[] cookies = request.getCookies();// 获取cookie对象 if (cookies != null) { for(Cookie cookie : cookies) { if (cookie.getName().equals("prodHist")) { String prodHist = cookie.getValue(); String[] ids = prodHist.split(","); for (String id : ids) { //查询数据库，查询对应的商品 Product p = dao.findById(id); //显示到浏览器 html += "" + p.getId() + " " + p.getProName() + " " + p.getPrice() + "<br/>"; } } } } html += "</body>"; html += "</html>"; writer.write(html); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }
商品详情
package servlet; import java.io.IOException; import java.io.PrintWriter; import java.util.Arrays; import java.util.Collection; import java.util.LinkedList; import javax.servlet.ServletException; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import dao.ProductDao; import entity.Product; /** * 显示商品详细 * @author Administrator * */ public class DetailServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html; charset=utf-8"); //1.获取编号 String id = request.getParameter("id"); //2.到数据库中查询对应编号的商品 ProductDao dao = new ProductDao(); Product product = dao.findById(id); //3.显示到浏览器 PrintWriter writer = response.getWriter(); String html = ""; html += "<html>"; html += "<head>"; html += "<title>显示商品详细</title>"; html += "</head>"; html += "<body>"; html += "<table border='1' align='center' width='300px'>"; if(product!=null){ html += "<tr><th>编号:</th><td>"+product.getId()+"</td></tr>"; html += "<tr><th>商品名称:</th><td>"+product.getProName()+"</td></tr>"; html += "<tr><th>商品型号:</th><td>"+product.getProType()+"</td></tr>"; html += "<tr><th>商品价格:</th><td>"+product.getPrice()+"</td></tr>"; } html += "</table>"; html += "<center><a href='"+request.getContextPath()+"/ListServlet'>[返回列表]</a></center>"; html += "</body>"; html += "</html>"; writer.write(html); /** * 创建cookie，并发送 */ //1.创建cookie Cookie cookie = new Cookie("prodHist", createValue(request, id)); cookie.setMaxAge(1*60*60);//一个月 //2.发送cookie response.addCookie(cookie); } /* * 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） * @return */ public String createValue(HttpServletRequest request, String id) { Cookie[] cookies = request.getCookies(); String prodhist = null; if (cookies != null) { for(Cookie cookie : cookies) { if(cookie.getName().equals("prodhist")) { prodhist = cookie.getValue(); break; } } } // null或没有prodHist if (cookies == null || prodhist == null) { // 直接返回传入的id return id; } // 3,21 2 //String -> String[] -> Collection :为了方便判断重复id String[] ids = prodhist.split(","); Collection<String> colls = Arrays.asList(ids); // LinkedList 方便地操作（增删改元素）集合 // Collection -> LinkedList LinkedList<String> list = new LinkedList<String>(colls); //不超过3个 if(list.size() < 3) { if(list.contains(id)) { //去除重复id，把传入的id放最前面 list.remove(id); list.addFirst(id); } else { //直接把传入的id放最前面 list.addFirst(id); } } else { //等于3个 //id重复 if(list.contains(id)){ //去除重复id，把传入的id放最前面 list.remove(id); list.addFirst(id); }else{ //去最后的id，把传入的id放最前面 list.removeLast(); list.addFirst(id); } } // LinedList -> String StringBuffer sb = new StringBuffer(); for (Object obj : list) { sb.append(obj + ","); } //去掉最后的逗号 String result = sb.toString(); result = result.substring(0, result.length()-1); return result; } }
dao
package dao; import java.util.ArrayList; import java.util.List; import entity.Product; public class ProductDao { //模拟"数据库",存放所有商品数据 private static List<Product> data = new ArrayList<Product>(); /** * 初始化商品数据 */ static { //只执行一次 for(int i=1; i<=10; i++) { data.add(new Product("" + i, "笔记本" + i , "LN00" + i,34.0 + i )); } } /** * 提供查询所有商品的方法 */ public List<Product> findAll() { return data; } /** * 提供根据编号查询商品的方法 */ public Product findById(String id) { for (Product p : data) { if(p.getId().equals(id)) { return p; } } return null; } }