cookie的应用——浏览记录 - tzzt01

公告

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() + "&nbsp;" + p.getProName() + "&nbsp;" + 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;
    }
}

posted on 2017-08-14 16:29 tzzt01 阅读(170) 评论(0) 编辑收藏举报

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