1.什么是数据分页：数据分页就是将很多条记录像书本一样分页，每页显示多少行记录；

2.为什么要数据分页：当我们进行sql语句查询时，假如数据有成千上万行记录，如果在同一个页面去显示，那这个页面得有多大，数据就要很多，而我们所需的记录又很少，不使用分页，查看起来那么繁琐，而且一不小心容易看着眼花。使用数据分页，就行书本一样，有页数，一目了然。相当简洁。

3.核心sql语句：SELECT * FROM stud LIMIT m,n ————m表示要显示的页数，n表示显示的记录行数

4.核心思想：

• 总行数(rows): select count(1) from stud;每页显示的行数(PAGE_SIZE): 固定值---已知的一个常量页数: pageSize= num/n + (num%n==0)?0:1 当前页号: currentPage当前要显示的页面数据的起始行号和终止行号 :startRow: (currentPage-1)*pageSize如何显示从startN开始的pageSize条记录 select * from stud limit startN, pageSize;当前显示的开始页号：showStart=currentPage-showSize/2;当前显示的结束页号：showEnd=showStart+showSize-1;模糊查询：select count(*) from stud where 1=1 and........

  5.成果图：

  6.代码实现

  需要的包和配置文件：

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  1. myConUtil.jar----自己写的c3p0pool工具类
  2. commons-dbutils-1.4.jar
  3. mysql-connector-java-5.1.34-bin.jar
  4. c3p0-0.9.1.2.jar
  5. c3p0-config.xml

     index.jsp

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     1. <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
     2. <%@taglib prefix="c" uri="java.sun/jsp/jstl/core" %>
     8. 查看分页技术

     10. show,jsp

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         学号	姓名
         ${stud.id }	${stud.name }

         1. <%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
         2. <%@taglib prefix="c" uri="java.sun/jsp/jstl/core"%>
         8. media="screen">
         9. <script type="text/javascript">
         10. function onsub(obj){
         11. window.location.href="https://2cto/database/201608/"+obj.value;
         12. }
         13. </script>

         17. 以下是当前页的内容

         19. • 请输入要查询的关键字：
             • 学号:
             • 姓名:
     12. 上一页
     17. href="">${idx}
     22. ${idx}
     27. 下一页
     33. nchange="onsub(this)">selected="selected" value="${i}" > 第 ${i } 页

     35. table.css

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         1. table{
         2. color: green;
         3. border: 1px solid blue;
         4. border-collapse: collapse;
         5. width:500px;
         6. margin: auto;
         7. }
         8. td{
         9. border: 1px solid blue;
         10. }
         11. th{
         12. border: 1px solid blue;
         13. }
         14. body{
         15. text-align: center;
         16. }

             PageServlet.Java

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             1. package cn.hncu.page1.servlet;
             3. import java.io.IOException;
             4. import java.sql.SQLException;
             5. import java.util.Map;
             7. import javax.servlet.ServletException;
             8. import javax.servlet.http.HttpServlet;
             9. import javax.servlet.http.HttpServletRequest;
             10. import javax.servlet.http.HttpServletResponse;
             12. import cn.hncu.page1.domain.Stud;
             13. import cn.hncu.page1.service.IPageService;
             14. import cn.hncu.page1.service.PageService;
             16. public class PageServlet extends HttpServlet {
             17. private IPageService service=new PageService();
             19. public void doGet(HttpServletRequest request, HttpServletResponse response)
             20. throws ServletException, IOException {
             22. doPost(request, response);
             23. }
             26. public void doPost(HttpServletRequest request, HttpServletResponse response)
             27. throws ServletException, IOException {
             28. request.setCharacterEncoding("utf-8");
             29. //这里是搜索区域的操作
             30. Stud stud=null;
             31. if(request.getMethod().equals("POST")){
             32. if (stud==null) {
             33. stud = new Stud();
             34. }
             35. String serachId = request.getParameter("serachId");
             36. String serachName = request.getParameter("serachName");
             37. stud.setId(serachId);
             38. stud.setName(serachName);
             39. request.getSession().setAttribute("stud", stud);
             40. }else{
             41. stud=(Stud) request.getSession().getAttribute("stud");
             42. if (stud==null) {
             43. stud = new Stud();
             44. }
             45. }
             49. //封装studs对象
             50. int currentPage=1;
             51. try {
             52. currentPage = Integer.parseInt(request.getParameter("page"));
             53. } catch (NumberFormatException e) {
             54. currentPage=1;
             55. }
             56. Map map=null;
             57. try {
             58. map=service.query(currentPage,stud);
             59. } catch (SQLException e) {
             60. e.printStackTrace();
             61. }
             62. map.put("currentPage", currentPage);
             63. //显示滚动页号
             64. int showStart=0;//从第几个页号开始显示
             65. int showEnd=0;//从第几个页号结束显示
             66. int showSize=10;//显示多少页数
             67. int pageCount=Integer.parseInt(""+map.get("pageCount"));
             68. if(showSize>pageCount){//显示页数大于于总页数
             69. showStart=1;
             70. showEnd=pageCount;
             71. }else{
             72. if(currentPage<=showSize/2){
             73. showStart=1;
             74. showEnd=showSize;
             75. }else{
             76. showStart=currentPage-showSize/2;
             77. showEnd=showStart+showSize-1;
             78. }
             79. }
             80. if(showEnd>pageCount){
             81. showEnd=pageCount;
             82. showStart=showEnd-showSize;
             83. }
             84. map.put("showStart", showStart);
             85. map.put("showEnd", showEnd);
             87. request.setAttribute("map", map);
             88. request.getRequestDispatcher("/jsps/show.jsp").forward(request, response);
             89. }
             91. }

                 IPageService.java

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                 1. package cn.hncu.page1.service;
                 3. import java.sql.SQLException;
                 4. import java.util.Map;
                 6. import cn.hncu.page1.domain.Stud;
                 8. public interface IPageService {
                 9. public Map query(int currentPage, Stud stud) throws SQLException;
                 11. }
                 12. PageService.java[html] view plain copy
                     1. package cn.hncu.page1.service;
                     3. import java.sql.SQLException;
                     4. import java.util.Map;
                     6. import cn.hncu.page1.dao.PageDao;
                     7. import cn.hncu.page1.dao.PageDaoJdbc;
                     8. import cn.hncu.page1.domain.Stud;
                     10. public class PageService implements IPageService{
                     11. private PageDao dao=new PageDaoJdbc();
                     12. @Override
                     13. public Map query(int currentPage, Stud stud)
                     14. throws SQLException {
                     15. return dao.query(currentPage,stud);
                     16. }
                     18. } PageDao.java[html] view plain copy
                         1. package cn.hncu.page1.dao;
                         3. import java.sql.SQLException;
                         4. import java.util.Map;
                         6. import cn.hncu.page1.domain.Stud;
                         8. public interface PageDao {
                         9. public Map query(int currentPage, Stud stud) throws SQLException;
                         11. } PageDaoJdbc.java[html] view plain copy
                             1. package cn.hncu.page1.dao;
                             3. import java.sql.SQLException;
                             4. import java.util.HashMap;
                             5. import java.util.List;
                             6. import java.util.Map;
                             8. import javax.sql.DataSource;
                             10. import org.apachemons.dbutils.QueryRunner;
                             11. import org.apachemons.dbutils.handlers.MapListHandler;
                             12. import org.apachemons.dbutils.handlers.ScalarHandler;
                             13. import org.junit.Test;
                             15. import cn.hncu.page1.domain.Stud;
                             16. import cn.hncu.page1.service.IPageService;
                             17. import cn.hncu.pool.C3p0Pool;
                             19. public class PageDaoJdbc implements PageDao{
                             20. private static final int PAGE_SIZE=10;
                             21. @Override
                             22. public Map query(int currentPage, Stud stud) throws SQLException {
                             23. Map map=new HashMap();
                             24. DataSource pool=C3p0Pool.getPool();
                             25. QueryRunner qr=new QueryRunner(pool);
                             26. String sql="select count(*) from stud where 1=1 ";
                             27. if(stud.getId()!=null&&stud.getId().trim().length()>0){
                             28. sql+="and id like '%"+stud.getId()+"%'";
                             29. }
                             30. if(stud.getName()!=null&&stud.getName().trim().length()>0){
                             31. sql+="and name like '%"+stud.getName()+"%'";
                             32. }
                             34. int rows=Integer.parseInt(""+ qr.query(sql, new ScalarHandler()));
                             35. int pageCount=rows/PAGE_SIZE+((rows%PAGE_SIZE==0)?0:1);
                             36. map.put("pageCount", pageCount);
                             38. int startRow=(currentPage-1)*PAGE_SIZE;
                             39. map.put("startRow", startRow);
                             41. String sql2="select * from stud where 1=1 ";//这种判断方法，很不错
                             42. if(stud.getId()!=null&&stud.getId().trim().length()>0){
                             43. sql2+="and id like '%"+stud.getId()+"%'";
                             44. }
                             45. if(stud.getName()!=null&&stud.getName().trim().length()>0){
                             46. sql2+="and name like '%"+stud.getName()+"%' ";
                             47. }
                             48. sql2+="limit "+startRow+" , "+PAGE_SIZE;
                             49. List> datas=qr.query(sql2, new MapListHandler());
                             50. map.put("datas", datas);
                             51. return map;
                             52. }
                             55. }

                                 Stud.java

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                                 1. package cn.hncu.page1.domain;
                                 3. public class Stud {
                                 4. private String id;
                                 5. private String name;
                                 6. public String getId() {
                                 7. return id;
                                 8. }
                                 9. public void setId(String id) {
                                 10. this.id = id;
                                 11. }
                                 12. public String getName() {
                                 13. return name;
                                 14. }
                                 15. public void setName(String name) {
                                 16. this.name = name;
                                 17. }
                                 18. @Override
                                 19. public String toString() {
                                 20. return "Stud [id=" + id + ", name=" + name + "]";
                                 21. }
                                 23. }