【jsp】案例：显示商品列表 & 问题：List内添加元素，为什么值都变成一样的了
代码：
1.Product：
1 package domain; 2 3 public class Product { 4 5 /* `pid` varchar(50) NOT NULL, 6 `pname` varchar(150) DEFAULT NULL, 7 `market_price` double DEFAULT NULL, 8 `shop_price` double DEFAULT NULL, 9 `pimage` varchar(200) DEFAULT NULL, 10 `pdate` date DEFAULT NULL, 11 `is_hot` int(11) DEFAULT NULL, 12 `pdesc` varchar(255) DEFAULT NULL, 13 `pflag` int(11) DEFAULT NULL, 14 `cid` varchar(50) DEFAULT NULL, 15 PRIMARY KEY (`pid`)*/ 16 17 private String pid; 18 private String pname; 19 private double market_price; 20 private double shop_price; 21 private String pimage; 22 private String pdate; 23 private int is_hot; 24 private String pdesc; 25 private int pflag; 26 private String cid; 27 28 public Product(){ 29 pid=""; 30 pname=""; 31 pimage=""; 32 pdate=""; 33 pdesc=""; 34 cid=""; 35 } 36 37 public String getPid() { 38 return pid; 39 } 40 public void setPid(String pid) { 41 this.pid = pid; 42 } 43 public String getPname() { 44 return pname; 45 } 46 public void setPname(String pname) { 47 this.pname = pname; 48 } 49 public double getMarket_price() { 50 return market_price; 51 } 52 public void setMarket_price(double market_price) { 53 this.market_price = market_price; 54 } 55 public double getShop_price() { 56 return shop_price; 57 } 58 public void setShop_price(double shop_price) { 59 this.shop_price = shop_price; 60 } 61 public String getPimage() { 62 return pimage; 63 } 64 public void setPimage(String pimage) { 65 this.pimage = pimage; 66 } 67 public String getPdate() { 68 return pdate; 69 } 70 public void setPdate(String pdate) { 71 this.pdate = pdate; 72 } 73 public int getIs_hot() { 74 return is_hot; 75 } 76 public void setIs_hot(int is_hot) { 77 this.is_hot = is_hot; 78 } 79 public String getPdesc() { 80 return pdesc; 81 } 82 public void setPdesc(String pdesc) { 83 this.pdesc = pdesc; 84 } 85 public int getPflag() { 86 return pflag; 87 } 88 public void setPflag(int pflag) { 89 this.pflag = pflag; 90 } 91 public String getCid() { 92 return cid; 93 } 94 public void setCid(String cid) { 95 this.cid = cid; 96 } 97 98 }
2.ProductListD
1 package dao; 2 3 import java.sql.*; 4 import java.util.ArrayList; 5 import java.util.List; 6 7 import domain.Product; 8 9 public class ProductListDao { 10 11 public List<Product> getAllProduct(){ 12 List<Product> productList=new ArrayList<Product>();//List是接口，不能直接new List 13 // Product product=new Product();//不能只定义一个变量，页面上只显示最后一个商品 14 15 try { 16 Class.forName("com.mysql.jdbc.Driver"); 17 } catch (ClassNotFoundException e) { 18 e.printStackTrace(); 19 } 20 try { 21 Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/web17","root","root"); 22 PreparedStatement ps=con.prepareStatement("select * from product"); 23 ResultSet rs=ps.executeQuery(); 24 // int i=0; 25 while(rs.next()) { 26 Product product=new Product(); 27 28 product.setPid(rs.getString(1)); 29 product.setPname(rs.getString(2)); 30 product.setMarket_price(rs.getInt(3)); 31 product.setShop_price(rs.getInt(4)); 32 product.setPimage(rs.getString(5)); 33 product.setPdate(rs.getString(6)); 34 product.setIs_hot(rs.getInt(7)); 35 product.setPdate(rs.getString(8)); 36 product.setPflag(rs.getInt(9)); 37 product.setCid(rs.getString(10)); 38 39 // System.out.println(product.getPname()); 40 productList.add(product); 41 // System.out.println(productList.get(i).getPname()); 42 // i++; 43 } 44 45 rs.close(); 46 ps.close(); 47 con.close(); 48 } catch (SQLException e) { 49 e.printStackTrace(); 50 } 51 52 return productList; 53 } 54 55 }
3.ProductListServlet
1 package servlet; 2 3 import java.io.IOException; 4 import java.util.List; 5 6 import javax.servlet.ServletException; 7 import javax.servlet.http.HttpServlet; 8 import javax.servlet.http.HttpServletRequest; 9 import javax.servlet.http.HttpServletResponse; 10 11 import dao.ProductListDao; 12 import domain.Product; 13 14 public class ProductListServlet extends HttpServlet { 15 16 protected void doGet(HttpServletRequest request, HttpServletResponse response) 17 throws ServletException, IOException { 18 19 ProductListDao productListDao=new ProductListDao(); 20 List<Product> productList=productListDao.getAllProduct(); 21 // System.out.println(productList.isEmpty()); 22 23 request.setAttribute("productList", productList); 24 request.getRequestDispatcher("/product_list.jsp").forward(request, response); 25 26 } 27 28 protected void doPost(HttpServletRequest request, HttpServletResponse response) 29 throws ServletException, IOException { 30 doGet(request, response); 31 } 32 33 }
4.product_list.jsp
1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2 pageEncoding="UTF-8"%> 3 <%@ page import="java.util.*"%> 4 <%@ page import="domain.*"%> 5 <!DOCTYPE html> 6 <html> 7 <head> 8 <meta name="viewport" content="width=device-width, initial-scale=1"> 9 <title>会员登录</title> 10 <link rel="stylesheet" href="css/bootstrap.min.css" type="text/css" /> 11 <script src="js/jquery-1.11.3.min.js" type="text/javascript"></script> 12 <script src="js/bootstrap.min.js" type="text/javascript"></script> 13 <!-- 引入自定义css文件 style.css --> 14 <link rel="stylesheet" href="css/style.css" type="text/css" /> 15 16 <style> 17 body { 18 margin-top: 20px; 19 margin: 0 auto; 20 width: 100%; 21 } 22 23 .carousel-inner .item img { 24 width: 100%; 25 height: 300px; 26 } 27 </style> 28 </head> 29 30 <body> 31 32 33 <!-- 引入header.jsp --> 34 <jsp:include page="/header.jsp"></jsp:include> 35 36 37 <div class="row" style="width: 1210px; margin: 0 auto;"> 38 <div class="col-md-12"> 39 <ol class="breadcrumb"> 40 <li><a href="#">首页</a></li> 41 </ol> 42 </div> 43 44 <% 45 List<Product> productList = (List<Product>) request.getAttribute("productList"); 46 47 if (productList != null) { 48 for (Product product : productList) { 49 50 out.write("<div class='col-md-2'>"); 51 out.write("<a href='product_info.htm'> <img src='"+product.getPimage()+"' width='170' height='170' style='display: inline-block;'>"); 52 out.write("</a>"); 53 out.write("<p>"); 54 out.write("<a href='product_info.html' style='color: green'>"+product.getPname()+"</a>"); 55 out.write("</p>"); 56 out.write("<p>"); 57 out.write("<font color='#FF0000'>商城价：¥"+product.getShop_price()+"</font>"); 58 out.write("</p>"); 59 out.write("</div>"); 60 61 } 62 } 63 %> 64 65 </div> 66 67 <!--分页 --> 68 <div style="width: 380px; margin: 0 auto; margin-top: 50px;"> 69 <ul class="pagination" style="text-align: center; margin-top: 10px;"> 70 <li class="disabled"><a href="#" aria-label="Previous"><span 71 aria-hidden="true">«</span></a></li> 72 <li class="active"><a href="#">1</a></li> 73 <li><a href="#">2</a></li> 74 <li><a href="#">3</a></li> 75 <li><a href="#">4</a></li> 76 <li><a href="#">5</a></li> 77 <li><a href="#">6</a></li> 78 <li><a href="#">7</a></li> 79 <li><a href="#">8</a></li> 80 <li><a href="#">9</a></li> 81 <li><a href="#" aria-label="Next"> <span aria-hidden="true">»</span> 82 </a></li> 83 </ul> 84 </div> 85 <!-- 分页结束 --> 86 87 <!--商品浏览记录--> 88 <div 89 style="width: 1210px; margin: 0 auto; padding: 0 9px; border: 1px solid #ddd; border-top: 2px solid #999; height: 246px;"> 90 91 <h4 style="width: 50%; float: left; font: 14px/30px 微软雅黑">浏览记录</h4> 92 <div style="width: 50%; float: right; text-align: right;"> 93 <a href="">more</a> 94 </div> 95 <div style="clear: both;"></div> 96 97 <div style="overflow: hidden;"> 98 99 <ul style="list-style: none;"> 100 <li 101 style="width: 150px; height: 216; float: left; margin: 0 8px 0 0; padding: 0 18px 15px; text-align: center;"><img 102 src="products/1/cs10001.jpg" width="130px" height="130px" /></li> 103 </ul> 104 105 </div> 106 </div> 107 108 109 <!-- 引入footer.jsp --> 110 <jsp:include page="/footer.jsp"></jsp:include> 111 112 </body> 113 114 </html>
结果：
http://localhost:8080/WEB17_2/ProductListServlet
注意：
加入List内的元素只保存了地址，而不是复制元素。将元素加入List后，修改该元素值，会影响到List内的元素值。所以每次放入一个新元素都需要new一个新地址。否则结果只有最后一个元素值，前面的元素值都被覆盖了。
