需求说明：
• 演示最终分页效果
• 提供分页素材
• 分页的作用
• 数据量大，一页容不下
• 后台查询部分数据而不是全部数据
• 降低带宽使用，提高访问速度
• 分页的实现思路
• MVC四个层次都需要参与分页操作SXT SXT 练习2——理解PageBean
• 需求说明：
• 提供面向对象的PageBean，降低分页难度，实现功能重用
• 理解PageBean的属性和方法
• 分页的三个基本属性
• 1.每页几条记录size 可以有默认值5
• 2.当前页号 index 可以有默认值1
• 3.记录总数totalCount：没有默认值，需查询数据库获取真正记录总数
• 分页的其他属性
• 一共多少页 ：totalPageCount=totalCount/size+1
• 上一页 index-1 当前页1，上一页1
• 下一页 index+1 当前页是最后一页 下一页：还是最后一页
• 扩展
• 分页Bean还可以放要查询的数据 protected List<T> list;
• 分页Bean还可以放页码列表 [1] 2 3 4 5 private int[] numbers;SXT SXT 练习2——理解PageBean
• public class PageBean<T> {
private int size = 5;//每页显示记录
private int index = 1;// 当前页号
private int totalPageCount = 1;// 总页数
private int totalCount = 0;// 记录总数
private int[] numbers;//展示页数集合
protected List<T> list;//要显示到页面的数据集
//赋值记录总数
public void setTotalCount(int totalCount) {}
//根据记录总数计算总页数
private void setTotalPageCountByRs() {}
//根据总页数计算页面显示的页号范围
public void setNumbers(int totalPageCount) {}
• }SXT SXT
练习2——理解PageBean
• 需要根据当前页和总页数的关系确定显示的页码
• 情况1：总页数21，当前14
• 9 10 11 12 13 [14] 15 16 17 18
• 情况2：总页数21，当前1,2,3,4
• 1 2 [3] 4 5 6 7 8 9 10
• 情况3：总页数21，当前19,20,21
• 12 13 14 15 16 17 [18] 19 20 21
• 情况4：总页数不够10页
• 1 2 [3] 4 5SXT SXT
练习3——实现基本分页的后台操作
• 需求说明：
• 控制层
• 获取当前页号
• 将当前页号给PageBean
• 传递PageBean到业务层
• 业务层
• 获取记录总数
• 使用记录总数计算PageBean其他属性值
• 调用数据访问层获取当前页数据并给PageBean
• 数据访问层
• 分页查询语句 String sql = "select * from (select rownum r,e2.* from "
+ "( select e.* from student e order by score desc) e2 "
+ "where rownum<="+end+" ) where r>"+startSXT SXT
练习4——实现基本分页的页面显示
• 需求说明：
• 视图层显示分页
• 使用JSTL/EL完成分页数据显示
练习5——完善基本分页
• 需求说明：
• 数据访问层
• 理解分页查询语句：
• Oracle :复杂 三层子查询
• MySQL：简单 select * from student limit 5,5//start,size
• 业务层
• 直接获取记录总数 select count (*) from student
• 视图层
• 改变每页记录数
• 直接跳到某一页
• 代码优化，提取JS方法
• 控制层
• 取当前页号和每页记录数
function change(index,size){
location.href="servlet/ShowAllServlet
?index="+index+"&size="+size;
}
练习6——带条件查询的分页
• 需求说明：
• 视图层：
• 查询表单
• 记忆查询条件
• 控制层：
• 获取表单数据，将表单数据（查询条件）传递到业务层
• 业务层：
• 获取符合查询条件的记录总数
• 获取符合查询条件的记录数据
• DAO层:
• 改变SQL查询语句，需要根据查询条件拼接SQL语句
练习7——完善带条件查询的分页
• 需求说明：
• 点击页码超链接的同时要提交表单
• 实现1：修改form的action属性
• document.forms[0].action="servlet/ShowAllServlet?index="+index+"&size="+size;
• 实现2：给表单添加hidden属性，表示index和size
• <input type="hidden" id="index" name="index" >
• <input type="hidden" id="size" name="size" >
• document.getElementById("index").value=index;
• document.getElementById("size").value=size;
• 实现直接输入页号并提交
• 与上个功能类似
• 更新删除后仍旧跳回当前页，而不是第一页
详细代码如下：
pageBean.java
package com.briup.common.util; import java.util.List; /** * 分页的三个基本属性 * 1.每页几条记录size 可以有默认值5 * 2.当前页号 index 可以有默认值1 * 3.记录总数totalCount：不可能有默认值，需要查询数据库获取真正的记录总数 * * 4.一共多少页 ：totalPageCount=totalCount/size+1 * 5 30 31 32 33 34 35 * 5.上一页 index-1 当前页1，上一页1 * 6.下一页 index+1 当前页是最后一页 下一页：还是最后一页 * * 扩展 * 分页Bean还可以放要查询的数据 protected List<T> list; * 分页Bean还可以放页码列表 [1] 2 3 4 5 private int[] numbers; * * @author Administrator * * @param <T> */ public class PageBean<T> { private int size = 5;//每页显示记录 // private int index = 1;// 当前页号 private int totalCount = 0;// 记录总数 ok private int totalPageCount = 1;// 总页数 ok private int[] numbers;//展示页数集合 //ok protected List<T> list;//要显示到页面的数据集 /** * 得到开始记录 * @return */ public int getStartRow() { return (index - 1) * size; } /** * 得到结束记录 * @return */ public int getEndRow() { return index * size; } /** * @return Returns the size. */ public int getSize() { return size; } /** * @param size * The size to set. */ public void setSize(int size) { if (size > 0) { this.size = size; } } /** * @return Returns the currentPageNo. */ public int getIndex() { if (totalPageCount == 0) { return 0; } return index; } /** * @param currentPageNo * The currentPageNo to set. */ public void setIndex(int index) { if (index > 0) { this.index = index; } } /** * @return Returns the totalCount. */ public int getTotalCount() { return totalCount; } /** * @param totalCount * The totalCount to set. */ public void setTotalCount(int totalCount) { if (totalCount >= 0) { this.totalCount = totalCount; setTotalPageCountByRs();//根据总记录数计算总页�? } } public int getTotalPageCount() { return this.totalPageCount; } /** * 根据总记录数计算总页�? * 5 * 20 4 * 23 5 */ private void setTotalPageCountByRs() { if (this.size > 0 && this.totalCount > 0 && this.totalCount % this.size == 0) { this.totalPageCount = this.totalCount / this.size; } else if (this.size > 0 && this.totalCount > 0 && this.totalCount % this.size > 0) { this.totalPageCount = (this.totalCount / this.size) + 1; } else { this.totalPageCount = 0; } setNumbers(totalPageCount);//获取展示页数集合 } public int[] getNumbers() { return numbers; } /** * 设置显示页数集合 * * 默认显示10个页码 * 41 42 43 44 [45 ] 46 47 48 49 50 * * * [1] 2 3 4 5 6 7 8 9 10 * * 41 42 43 44 45 46 47 [48] 49 50 * @param totalPageCount */ public void setNumbers(int totalPageCount) { if(totalPageCount>0){ //!.当前数组的长度 int[] numbers = new int[totalPageCount>10?10:totalPageCount];//页面要显示的页数集合 int k =0; // //1.数组长度<10 1 2 3 4 .... 7 //2.数组长度>=10 // 当前页<=6 1 2 3 4 10 // 当前页>=总页数-5 ......12 13 14 15 // 其他 5 6 7 8 9 当前页(10) 10 11 12 13 for(int i = 0;i < totalPageCount;i++){ //保证当前页为集合的中�? if((i>=index- (numbers.length/2+1) || i >= totalPageCount-numbers.length) && k<numbers.length){ numbers[k] = i+1; k++; }else if(k>=numbers.length){ break; } } this.numbers = numbers; } } public void setNumbers(int[] numbers) { this.numbers = numbers; } public List<T> getList() { return list; } public void setList(List<T> list) { this.list = list; } /* public static int getTotalPageCount(int iTotalRecordCount, int iPageSize) { if (iPageSize == 0) { return 0; } else { return (iTotalRecordCount % iPageSize) == 0 ? (iTotalRecordCount / iPageSize) : (iTotalRecordCount / iPageSize) + 1; } }*/ }
pojo
Customer.java
package com.briup.bean; import java.io.Serializable; public class Customer implements Serializable{ private static final long serialVersionUID = -1415977267636644567L; private Long id; private String name; private String password; private String zip; private String address; private String telephone; private String email; public Customer() { } public Customer(Long id, String name, String password, String zip, String address, String telephone, String email) { super(); this.id = id; this.name = name; this.password = password; this.zip = zip; this.address = address; this.telephone = telephone; this.email = email; } public Customer(String name, String password, String zip, String address, String telephone, String email) { super(); this.name = name; this.password = password; this.zip = zip; this.address = address; this.telephone = telephone; this.email = email; } public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public String getZip() { return zip; } public void setZip(String zip) { this.zip = zip; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } public String getTelephone() { return telephone; } public void setTelephone(String telephone) { this.telephone = telephone; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } }
dao
package com.briup.dao; import java.util.List; import com.briup.bean.Customer; import com.briup.bean.Student; public interface StudentDao { /** * ��ѯ����ѧ�� * @return */ public List<Customer> findAll(); /** * ��ѯָ����Χ��ѧ�� * @param start * @param end * @return */ public List<Customer> findStu(int start, int size); /** * ��ѯ��¼���� * @return */ public int findCount(); /** * ��ѯ��ϲ�ѯ�����ļ�¼���� * @param name * @param minScore * @return */ public int findCount(String name); /** * ��ѯ��ϲ�ѯ������ָ��ҳ���ѧ�� * @param start * @param end * @param name * @param minScore * @return */ public List<Customer> findStu(int start, int size, String name); }
dao.impl
package com.briup.dao.impl; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.List; import com.briup.bean.Customer; import com.briup.bean.Student; import com.briup.common.util.DBUtil; import com.briup.dao.StudentDao; public class StudentDaoImpl implements StudentDao { public List<Customer> findAll() { Connection conn =DBUtil.getConnection(); Statement stmt =null; ResultSet rs =null; List<Customer> stuList = new ArrayList<Customer>(); try { stmt =conn.createStatement(); rs = stmt.executeQuery("select * from student"); while(rs.next()){ Customer cus1 = new Customer(); cus1.setId(rs.getLong("customer_id")); cus1.setAddress(rs.getString("address")); cus1.setEmail(rs.getString("email")); cus1.setName(rs.getString("name")); cus1.setPassword(rs.getString("password")); cus1.setTelephone(rs.getString("telephone")); cus1.setZip(rs.getString("zip")); stuList.add(cus1); } } catch (SQLException e) { e.printStackTrace(); }finally{ DBUtil.closeAll(rs, stmt, conn); } return stuList; } public List<Customer> findStu(int start, int size) { Connection conn =DBUtil.getConnection(); PreparedStatement pstmt =null; ResultSet rs =null; List <Customer> stuList = new ArrayList<Customer>(); try { String sql = "select * from tbl_customer limit ?,?"; pstmt =conn.prepareStatement(sql); pstmt.setInt(1, start); pstmt.setInt(2, size); rs = pstmt.executeQuery(); while(rs.next()){ /*private Long id; private String name; private String password; private String zip; private String address; private String telephone; private String email;*/ Customer cus1 = new Customer(); cus1.setId(rs.getLong("customer_id")); cus1.setAddress(rs.getString("address")); cus1.setEmail(rs.getString("email")); cus1.setName(rs.getString("name")); cus1.setPassword(rs.getString("password")); cus1.setTelephone(rs.getString("telephone")); cus1.setZip(rs.getString("zip")); stuList.add(cus1); } } catch (SQLException e) { e.printStackTrace(); }finally{ DBUtil.closeAll(rs, pstmt, conn); } return stuList; } public int findCount() { Connection conn =DBUtil.getConnection(); Statement stmt =null; ResultSet rs =null; List <Student> stuList = new ArrayList<Student>(); int count = 0; try { stmt =conn.createStatement(); rs = stmt.executeQuery("select count(*) from tbl_customer"); rs.next(); count = rs.getInt(1); } catch (SQLException e) { e.printStackTrace(); }finally{ DBUtil.closeAll(rs, stmt, conn); } return count; } public int findCount(String name) { Connection conn =DBUtil.getConnection(); Statement stmt =null; ResultSet rs =null; List <Student> stuList = new ArrayList<Student>(); int count = 0; try { StringBuilder sql = new StringBuilder("select count(*) from tbl_customer where 1=1 "); if(name != null && !"".equals(name)){ sql.append(" and name like '%"+name+"%'"); } stmt =conn.createStatement(); rs = stmt.executeQuery(sql.toString()); rs.next(); count = rs.getInt(1); System.out.println("StudentDaoImpl.findCount()"+count); } catch (SQLException e) { e.printStackTrace(); }finally{ DBUtil.closeAll(rs, stmt, conn); } return count; } public List<Customer> findStu(int start, int size, String name ) { Connection conn =DBUtil.getConnection(); Statement stmt =null; ResultSet rs =null; PreparedStatement pstmt=null; List<Customer> stuList = new ArrayList<Customer>(); try { stmt =conn.createStatement(); StringBuilder sql = new StringBuilder("select * from tbl_customer cus where 1=1 "); if(name != null && !"".equals(name)){ sql.append(" and name like '%"+name+"%'"); } sql.append(" order by score desc"); String sql2 = "select * from tbl_customer limit ?,?"; pstmt = conn.prepareStatement(sql2); pstmt.setInt(1, start); pstmt.setInt(2, size); rs = pstmt.executeQuery(); while(rs.next()){ Customer cus1 = new Customer(); cus1.setId(rs.getLong("customer_id")); cus1.setAddress(rs.getString("address")); cus1.setEmail(rs.getString("email")); cus1.setName(rs.getString("name")); cus1.setPassword(rs.getString("password")); cus1.setTelephone(rs.getString("telephone")); cus1.setZip(rs.getString("zip")); stuList.add(cus1); } } catch (SQLException e) { e.printStackTrace(); }finally{ DBUtil.closeAll(rs, stmt, conn); } return stuList; } }
Service
package com.briup.service; import java.util.List; import com.briup.bean.Customer; import com.briup.bean.Student; import com.briup.common.util.PageBean; public interface StudentService { /** * ��ѯ����ѧ�� * @return */ public List<Customer> findAll(); /** * ��ɻ�ķ�ҳ�����������ѯ������ * @param pageBean */ public void findStu(PageBean<Customer> pageBean); /** * ��ɷ�ҳ���������ѯ������ * @param pageBean */ public void findStu(PageBean<Customer> pageBean, String name); }
Service.impl
package com.briup.service.impl; import java.util.List; import com.briup.bean.Customer; import com.briup.bean.Student; import com.briup.common.util.PageBean; import com.briup.dao.StudentDao; import com.briup.dao.impl.StudentDaoImpl; import com.briup.service.StudentService; public class StudentServiceImpl implements StudentService { private StudentDao stuDao = new StudentDaoImpl(); public List<Customer> findAll() { return this.stuDao.findAll(); } public void findStu(PageBean<Customer> pageBean) { //��ѯ��ݿ���ȡ��¼���� //int totalCount = this.stuDao.findAll().size();//???? int totalCount = this.stuDao.findCount(); System.out.println("count="+totalCount); //ʹ�ü�¼�������PageBean�е���������(totalCount,totalPageCount,numbers)���Ͳ�list���� pageBean.setTotalCount(totalCount); //����DAO���ȡָ��ҳ��ѧ����ݣ�������pageBean��list���� /* *ÿҳsize = 5����¼ * �ڼ�ҳ ��ʼ��¼��>= �����¼��<= < * 1 0 4 5 * 2 5 9 10 * 3 10 14 15 * * index (index-1)*size index*size * */ //int start = (pageBean.getIndex()-1)*pageBean.getSize(); //int end= pageBean.getIndex()*pageBean.getSize(); int start = pageBean.getStartRow(); int end = pageBean.getEndRow(); int size = pageBean.getSize(); List<Customer> list = this.stuDao.findStu(start,size); pageBean.setList(list); } public void findStu(PageBean<Customer> pageBean, String name) { //��ѯ��ݿ���ȡ��ϲ�ѯ�����ļ�¼���� int totalCount = this.stuDao.findCount(name); System.out.println("count="+totalCount); //ʹ�ü�¼�������PageBean�е���������(totalCount,totalPageCount,numbers)���Ͳ�list���� pageBean.setTotalCount(totalCount); //����DAO���ȡָ��ҳ��ѧ����ݣ�������pageBean��list���� int start = pageBean.getStartRow(); int end = pageBean.getEndRow(); int size = pageBean.getSize(); List<Customer> list = this.stuDao.findStu(start,size,name); pageBean.setList(list); } }
Servlet
package com.briup.web.servlet; import java.io.IOException; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import com.briup.bean.Customer; import com.briup.common.util.PageBean; import com.briup.service.StudentService; import com.briup.service.impl.StudentServiceImpl; public class ShowAllServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { request.setCharacterEncoding("utf-8"); String sindex = request.getParameter("index"); // null "" int index = 1; System.out.println(index); try { index = Integer.parseInt(sindex);//"5" } catch (NumberFormatException e) { e.printStackTrace(); } String ssize = request.getParameter("size"); // null "" int size = 5; try { size = Integer.parseInt(ssize);//"5" } catch (NumberFormatException e) { e.printStackTrace(); } String name = request.getParameter("name"); // 2 PageBean<Customer> pageBean = new PageBean<Customer>(); pageBean.setIndex(index); pageBean.setSize(size); StudentService stuService = new StudentServiceImpl(); //List<Student> stuList = stuBiz.findAll(); //stuService.findStu(pageBean);//����Ҫ����stuList����Ϊ����ҵ��㴦�?���е���ݶ���PageBean�� stuService.findStu(pageBean,name); request.setAttribute("pageBean", pageBean);// !!!!!!! request.setAttribute("name", name); // 3com.bjsxt request.getRequestDispatcher("/jsp/showAll.jsp").forward(request, response); } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doGet(request, response); } }
jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> <% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <base href="<%=basePath%>"> <title>查询并显示所有学生信息</title> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"> <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"> <meta http-equiv="description" content="This is my page"> <!-- <link rel="stylesheet" type="text/css" href="styles.css"> --> <script type="text/javascript"> function changeIndex(index){ location.href="stu?index="+index; } function changeSize(size){ //alert(size); location.href= "stu?size="+size; } function change2(index,size){ //location.href="servlet/ShowAllServlet?index="+index+"&size="+size; document.forms[0].action="stu?index="+index+"&size="+size; document.forms[0].submit(); } function change(index,size){ document.forms[0].index.value = index; //document.forms[0].size.value = size; document.getElementById("size").value = size; document.forms[0].submit(); } </script> </head> <body> <hr> <form action="stu" method="post" id="form1"> <table align="center"> <tr> <td>姓名</td> <td> <input type="text" name="name" value="${name }"> <input type="hidden" name="index" value=""> <input type="hidden" id="size" name="size"> </td> <td><input type="submit" value="提交"></td> </tr> </table> </form> <hr> <!-- 显示所有学生 /stumanager/ --> <table align="center" border="1" width="60%"> <tr> <th>学生 编号</th> <th>学生姓名</th> <th>学生年龄</th> <th>学生成绩</th> <th>vs.index</th> <th>更新操作</th> <th>删除操作</th> </tr> <c:forEach items="${pageBean.list}" var="stu" varStatus="vs"> <tr> <td>${stu.id }</td> <td>${stu.name }</td> <td>${stu.password}</td> <td>${stu.zip }</td> <td>${stu.address }</td> <td>${stu.telephone }</td> <td>${stu.email }</td> <td>${vs.index }</td> <td><a href="/stumanager/servlet/StudentServlet?operate=preupdate&sid=${stu.id}">更新</a></td> <td><a href="/stumanager/servlet/StudentServlet?operate=delete&sid=${stu.id}">删除</a></td> </tr> </c:forEach> <tr> <td colspan="11" align="center"> <a href="javascript:change(1,${pageBean.size })">首页</a> <c:if test="${pageBean.index !=1 }"> <a href="javascript:change(${pageBean.index-1 },${pageBean.size })">上一页 </a> </c:if> <c:if test="${pageBean.index ==1 }"> 上一页 </c:if> <c:forEach items="${pageBean.numbers }" var="num"> <c:if test="${num ==pageBean.index }"> [<a href="javascript:change(${num },${pageBean.size })">${num }</a>] </c:if> <c:if test="${num != pageBean.index }"> <a href="javascript:change(${num },${pageBean.size })">${num }</a> </c:if> </c:forEach> <c:if test="${pageBean.index != pageBean.totalPageCount }"> <a href="javascript:change(${pageBean.index+1 },${pageBean.size })">下一页</a> </c:if> <c:if test="${pageBean.index == pageBean.totalPageCount }"> 下一页 </c:if> <a href="javascript:change(${pageBean.totalPageCount },${pageBean.size })">末页</a> 每页 <select onchange="change(${pageBean.index},this.value)"> <c:forEach begin="5" end="25" step="5" var="i"> <c:if test="${i==pageBean.size }"> <option value="${i }" selected="selected">${i }</option> </c:if> <c:if test="${i!=pageBean.size }"> <option value="${i }">${i }</option> </c:if> </c:forEach> </select> 条记录 直接跳到第 <select onchange="change(this.value,${pageBean.size})"> <c:forEach begin="1" end="${ pageBean.totalPageCount }" var="num"> <c:if test="${num == pageBean.index }"> <option value="${num }" selected="selected">${num }</option> </c:if> <c:if test="${num != pageBean.index }"> <option value="${num }">${num }</option> </c:if> </c:forEach> </select> 页 共${pageBean.totalCount }条记录 </td> </tr> </table> </body> </html>
分页细节分析见github。