案例-商品浏览历史记录

用户浏览过的商品.png

案例-商品浏览历史记录

entity

package gz.itcast.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 + "]";
    }
    
}

dao

package gz.itcast.dao;
import gz.itcast.entity.Product;
import java.util.ArrayList;
import java.util.List;
/**
 * 该类中存放对Prodcut对象的CRUD方法
 * @author APPle
 *
 */
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;
    }
}

servlet

package gz.itcast.servlet;
import gz.itcast.dao.ProductDao;
import gz.itcast.entity.Product;
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;
/**
 * 查询所有商品的servlet
 * @author APPle
 *
 */
public class ListServlet extends HttpServlet 
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        //1.读取数据库,查询商品列表
        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>";
                // /day11_hist/DetailServlet?id=1 访问DetailSErvlet的servlet程序,同时传递 名为id,值为1 的参数
                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/>";
        //取出prodHist的cookie
        Cookie[] cookies = request.getCookies();
        if(cookies!=null){
            for (Cookie cookie : cookies) {
                if(cookie.getName().equals("prodHist")){
                    String prodHist = cookie.getValue(); // 3,2,1
                    String[] ids = prodHist.split(",");
                    //遍历浏览过的商品id
                    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);
    }
}
package gz.itcast.servlet;
import gz.itcast.dao.ProductDao;
import gz.itcast.entity.Product;
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;
/**
 * 显示商品详细
 * @author APPle
 *
 */
public class DetailServlet extends HttpServlet {
    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*30*24*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
     */
    private 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 colls = Arrays.asList(ids); //<3,21>
        // LinkedList 方便地操作(增删改元素)集合
        // Collection -> LinkedList
        LinkedList list = new LinkedList(colls);
        //不超过3个
        if(list.size()<3){
            //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{
                //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 object : list) {
            sb.append(object+",");
        }
        //去掉最后的逗号
        String result = sb.toString();
        result = result.substring(0, result.length()-1);
        return result;
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }
}
最后修改:2019 年 06 月 05 日 01 : 01 AM

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