【Java】 Java分页功能实现，
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【Java】 Java分页功能实现，
实现步骤：
**
**
product模型类定义如下(根据自己的数据库而定)
**
package cn.jishupeng.bookstore.model;
public class Product {
private String id;
private String name;
private double price;
private String category;
private int pnum;
private String imgurl;
private String description;
public Product() {
}
public Product(String id, String name, double price, String category, int pnum, String imgurl, String description) {
this.id = id;
this.name = name;
this.price = price;
this.category = category;
this.pnum = pnum;
this.imgurl = imgurl;
this.description = description;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getPrice() {
return price;
}
public void setPrice(double price) {
this.price = price;
}
public String getCategory() {
return category;
}
public void setCategory(String category) {
this.category = category;
}
public int getPnum() {
return pnum;
}
public void setPnum(int pnum) {
this.pnum = pnum;
}
public String getImgurl() {
return imgurl;
}
public void setImgurl(String imgurl) {
this.imgurl = imgurl;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
@Override
public String toString() {
return "Product{" +
"id='" + id + '\'' +
", name='" + name + '\'' +
", price=" + price +
", category='" + category + '\'' +
", pnum=" + pnum +
", imgurl='" + imgurl + '\'' +
", description='" + description + '\'' +
'}';
}
}
1 定义一个pageResult模型用于存储分页相关信息， 实现代码如下：
**
package cn.jishupeng.bookstore.model;
import java.util.List;
public class PageResult<T> {
List<T> list;
long totalCount;
int pageSize = 4;
int totalPage;
int currentPage;
public PageResult() {
}
public PageResult(List<T> list, long totalCount, int pageSize, int totalPage, int currentPage) {
this.list = list;
this.totalCount = totalCount;
this.pageSize = pageSize;
this.totalPage = totalPage;
this.currentPage = currentPage;
}
public List<T> getList() {
return list;
}
public void setList(List<T> list) {
this.list = list;
}
public long getTotalCount() {
return totalCount;
}
public void setTotalCount(long totalCount) {
this.totalCount = totalCount;
}
public int getPageSize() {
return pageSize;
}
public void setPageSize(int pageSize) {
this.pageSize = pageSize;
}
public int getTotalPage() {
return totalPage;
}
public void setTotalPage(int totalPage) {
this.totalPage = totalPage;
}
public int getCurrentPage() {
return currentPage;
}
public void setCurrentPage(int currentPage) {
this.currentPage = currentPage;
}
@Override
public String toString() {
return "PageResult{" +
"totalCount=" + totalCount +
", pageSize=" + pageSize +
", totalPage=" + totalPage +
", currentPage=" + currentPage +
'}';
}
}
**
2. 创建一个IProductDao接口和ProductImpl实现类， 编写dao层代码：
**
dao/IProductDao.interface
package cn.jishupeng.bookstore.dao;
import cn.jishupeng.bookstore.model.Product;
import java.sql.SQLException;
import java.util.List;
public interface IProductDao {
/*
* 根据商品分类查询商品总数量
* */
public abstract long count(String category) throws SQLException;
/*
* 通过分类和页码数查找对应分类的商品详细信息, 将数据封装进一个列表并返回
* */
public abstract List<Product> findProductByCategoryAndCurrentPage(String category, int currentPage, int pageSize) throws SQLException;
}
/dao/ProductDaoImpl
package cn.jishupeng.bookstore.dao.daoImpl;
import cn.jishupeng.bookstore.dao.IProductDao;
import cn.jishupeng.bookstore.model.Product;
import cn.jishupeng.bookstore.utils.C3P0Util;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
public class ProductDaoImpl implements IProductDao {
@Override
public long count(String category) throws SQLException {
/*
* 定义一个初始化count变量
* */
long count=0;
QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
String sql = "select count(*) from products where 1=1";
/*
* 判断: 当参数category部位空对象, 并且不为空字符串, 才将category作为查询条件
* */
if (category != null && !"".equals(category)) {
sql += " and category = ?";
count = (long)qr.query(sql, new ScalarHandler(), category);
} else {
/*
* 否则就查询所有商品总数, new ScalarHandler()返回的是一个但行单列的数据, 类型为Object
* */
count = (long)qr.query(sql, new ScalarHandler());
}
return count;
}
@Override
public List<Product> findProductByCategoryAndCurrentPage(String category, int currentPage, int pageSize) throws SQLException {
QueryRunner qr = new QueryRunner(C3P0Util.getDataSource());
/*
* 技巧: 定义一个列表对象用于存储查询参数, 执行query查询的时候可以直接传入列表
* */
List<Object> list = new ArrayList<>();
String sql = "select * from products where 1=1";
if (category != null && !"".equals(category)) {
sql += " and category=?";
/*
* 当category有效, 则把参数放入列表中
* */
list.add(category);
}
/*
* 定义跳过数据条数skip和每次显示数据长度length
* */
int skip = (currentPage - 1) * pageSize;
int length = pageSize;
list.add(skip);
list.add(length);
sql += " limit ?,?";
return qr.query(sql, new BeanListHandler<Product>(Product.class), list.toArray());
}
public static void main(String[] args) throws SQLException {
IProductDao pDao = new ProductDaoImpl();
long count = pDao.count(null);
List<Product> products = pDao.findProductByCategoryAndCurrentPage(null, 1, 4);
System.out.println(count);
for (Product product : products) {
System.out.println(product);
}
}
}
**
3. 编写service代码
**
IProductService
package cn.jishupeng.bookstore.service;
import cn.jishupeng.bookstore.model.ModifyUser;
import cn.jishupeng.bookstore.model.PageResult;
import cn.jishupeng.bookstore.model.Product;
import cn.jishupeng.bookstore.model.User;
public interface IProductService {
/*
* 根据分类和当前页查找商品数据,
* 此方法需要将查询到的数据封装到PageResult<Product>中, 并且返回给前台
* */
public abstract PageResult<Product> findProductByCategoryAndCurrentPage(String category, int currentPage, int pageSize) throws Exception;
}
/service/ProductServiceImpl
package cn.jishupeng.bookstore.service.UserServiceImpl;
import cn.jishupeng.bookstore.dao.IProductDao;
import cn.jishupeng.bookstore.dao.daoImpl.ProductDaoImpl;
import cn.jishupeng.bookstore.model.PageResult;
import cn.jishupeng.bookstore.model.Product;
import cn.jishupeng.bookstore.service.IProductService;
import java.sql.SQLException;
import java.util.List;
public class ProductServiceImpl implements IProductService {
IProductDao proDao = new ProductDaoImpl();
@Override
public PageResult<Product> findProductByCategoryAndCurrentPage(String category, int currentPage, int pageSize) throws SQLException {
/*
* 实例化PageResult模型
* */
PageResult<Product> pr = new PageResult<>();
/*
* 获取并设置总商品数量
* */
long totalCount = proDao.count(category);
pr.setTotalCount(totalCount);
/*
* 获取并设置每页显示的数量
* */
pr.setCurrentPage(currentPage);
/*
* 计算并设置总页数totalPage
* */
int totalPage = (int)(totalCount % pr.getPageSize() == 0 ? totalCount / pr.getPageSize() : (totalCount / pr.getPageSize()) + 1);
pr.setTotalPage(totalPage);
/*
* 执行查询并设置 list
* */
List<Product> list = proDao.findProductByCategoryAndCurrentPage(category, currentPage, pageSize);
pr.setList(list);
/*
* 返回pageResult对象
* */
return pr;
}
}
**
4. servlet代码实现
**
package cn.jishupeng.bookstore.web.servlet;
import cn.jishupeng.bookstore.model.PageResult;
import cn.jishupeng.bookstore.model.Product;
import cn.jishupeng.bookstore.service.IProductService;
import cn.jishupeng.bookstore.service.UserServiceImpl.ProductServiceImpl;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
@WebServlet("/showProductByPage")
public class ShowProductByPageServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
IProductService productService = new ProductServiceImpl();
String category = req.getParameter("category");
String currentPage = req.getParameter("page");
int page = 1;
try {
if (currentPage != null && !currentPage.equals("")) {
page = Integer.parseInt(currentPage);
}
PageResult<Product> pageResult = productService.findProductByCategoryAndCurrentPage(category, page, 4);
req.setAttribute("pageResult", pageResult);
req.setAttribute("category", category);
req.getRequestDispatcher("/product_list.jsp").forward(req, resp);
} catch (Exception e) {
e.printStackTrace();
}
}
}
**
6.jsp页面功能
**
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>bookStore列表</title>
<%--导入css --%>
<link rel="stylesheet" href="css/main.css" type="text/css" />
</head>
<body class="main">
<jsp:include page="head.jsp" />
<jsp:include page="menu_search.jsp" />
<div id="divpagecontent">
<table width="100%" border="0" cellspacing="0">
<tr>
<td>
<div >
<a href="index.jsp">首页</a> > 计算机 > 图书列表
</div>
<table cellspacing="0" class="listcontent">
<tr>
<td>
<h1>商品目录</h1>
<hr />
<h1>计算机</h1> 共${pageResult.totalCount}种商品
<hr />
<div >
<img src="images/productlist.gif" width="100%" height="38" />
</div>
<table cellspacing="0" class="booklist">
<tr>
<c:forEach items="${pageResult.list}" var="product">
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/101.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:${product.name}<br />售价: ${product.price}</a>
</div></td>
</c:forEach>
<%--<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/102.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/103.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/104.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>--%>
</tr>
</table>
<%--<table cellspacing="0" class="booklist">
<tr>
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/101.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/102.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/103.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>
<td>
<div class="divbookpic">
<p>
<a href="product_info.jsp"><img src="bookcover/104.jpg" width="115"
height="129" border="0" /> </a>
</p>
</div>
<div class="divlisttitle">
<a href="product_info.jsp">书名:xxx<br />售价:xxx </a>
</div></td>
</tr>
</table>--%>
<div class="pagination">
第${pageResult.currentPage}页 / 共${pageResult.totalPage}页
<ul>
<c:if test="${pageResult.currentPage == 1}">
<li class="disablepage"><a href="${pageContext.request.contextPath}/showProductByPage?category=${category}&page=1">上一页>></a></li>
</c:if>
<c:if test="${pageResult.currentPage != 1}">
<li class="disablepage"><a href="${pageContext.request.contextPath}/showProductByPage?category=${category}&page=${pageResult.currentPage - 1}">上一页>></a></li>
</c:if>
<%--<li class="currentpage">1</li>--%>
<c:forEach begin="1" end="${pageResult.totalPage}" var="i">
<li><a href="${pageContext.request.contextPath}/showProductByPage?category=${category}&page=${i}">${i}</a>
</li>
</c:forEach>
<c:if test="${pageResult.currentPage == pageResult.totalPage}">
<li class="nextpage"><a href="${pageContext.request.contextPath}/showProductByPage?category=${category}&page=${pageResult.totalPage}">下一页>></a>
</li>
</c:if>
<c:if test="${pageResult.currentPage != pageResult.totalPage}">
<li class="nextpage"><a href="${pageContext.request.contextPath}/showProductByPage?category=${category}&page=${pageResult.currentPage + 1}">下一页>></a>
</c:if>
</ul>
</div>
</td>
</tr>
</table></td>
</tr>
</table>
</div>
<jsp:include page="foot.jsp" />
</body>
</html>
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