java分页的写法

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第一步：

首先需要到如各部分岁对应的包，例如数据库驱动的包，实体类的包，c3p0的包，以及c3p0的配置文件

创建数据库，创建数据库所对应的一个实体类，例如：student类，里边包含私有的属性，及set和get方法

第二步：

创建另一个关于分页的实体类，里边只包含5项，如下可见

package com.qf.javabean;import java.util.List;public class PagStudent<T> {    private int currentpage;//当前页    private int pagsize;//每页的数据量    private int totalpage;//总页数    private int totalcount;//总数据量    private List<T> list;public synchronized int getCurrentpage() {return currentpage;}public synchronized void setCurrentpage(int currentpage) {this.currentpage = currentpage;}public synchronized int getPagsize() {return pagsize;}public synchronized void setPagsize(int pagsize) {this.pagsize = pagsize;}public synchronized int getTotalpage() {return (int)Math.ceil(totalcount*1.0/pagsize);}     //记住需要删除一个方法，是算出来的，不是被设置的public synchronized int getTotalcount() {return totalcount;}public synchronized void setTotalcount(int totalcount) {this.totalcount = totalcount;}public synchronized List<T> getList() {return list;}public synchronized void setList(List<T> list) {this.list = list;}public PagStudent(int currentpage, int pagsize, int totalcount, List<T> list) {super();this.currentpage = currentpage;this.pagsize = pagsize;this.totalcount = totalcount;this.list = list;}public PagStudent() {super();}  }

第三步：创建JSP页面

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%><%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>My JSP 'StudentPaging.jsp' starting page</title>    <meta charset="UTF-8"><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">-->  </head><!-- Student [id=1, name=张无惧, sex=null, age=0, password=null, qq=null, phone=null, major=null, grade=null] -->  <body>      <table border="1px" align="center" width="90%" cellspacing="0px">      <tr>      <th colspan="9"><h1>学员信息展示平台</h1></th>      </tr>        <tr>             <th >学员编号</th>             <th >姓名</th>             <th >性别</th>             <th >年龄</th>             <th >密码</th>             <th >QQ号</th>             <th >手机号</th>             <th >专业</th>             <th >班级</th>          </tr>        <c:forEach items="${page.list }" var="it"> <!--      属性导航 -->           <tr>             <td>${it.id }</td>             <td>${it.name }</td>             <td>${it.sex }</td>             <td>${it.age }</td>             <td>${it.password }</td>             <td>${it.qq }</td>             <td>${it.phone }</td>             <td>${it.major }</td>             <td>${it.grade }</td>                    </tr>      </c:forEach>         </table>   <center>                <c:if test="${page.currentpage != 1 }">                        <a href="${pageContext.request.contextPath }/servlet/PagStudent?currentpage=${page.currentpage-1 }">[上一页]</a>                      </c:if>                  <!-- 表里中间位置   ${page.totalpage }-->             <c:forEach var="i" begin="1" end="${page.totalpage}" step="1">             <%--  <c:forEach var="i" begin="${i }" end="${(i+8)>page.totalpage?page.totalpage:(i+8) }" step="1">   --%>              <!--  当页数过多时，显示部分页数，随着页数的增大，隐藏前边页数，显示后边的页数 -->               <c:if test="${page.currentpage == i }">                   ${i }                   </c:if>                         <c:if test="${page.currentpage !=i }">                  <a href="${pageContext.request.contextPath }/servlet/PagStudent?currentpage=${i }">${i }</a>               </c:if>                </c:forEach>          <c:if test="${page.totalpage != page.currentpage }">             <a href="${pageContext.request.contextPath }/servlet/PagStudent?currentpage=${page.currentpage+1 }">[下一页]</a>           </c:if>                      <br/>                                  当前${page.currentpage }/总共${page.totalpage }      </center>  </body></html>

第四步：创建servlet，里边包含（获取数据，调用逻辑，转发或重定向）

package com.qf.web;import java.io.IOException;import java.sql.SQLException;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.qf.javabean.Student;import com.qf.service.StudentService;public class PagStudent extends HttpServlet {private static final long serialVersionUID = 1L;public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8");int currentpage = Integer.parseInt(request.getParameter("currentpage"));// 当第一次访问的时候应该从请求中传递一个页数// System.out.println(currentpage+"获取了数据");int pagesize = 5;// 控制每页显示的数据量try {com.qf.javabean.PagStudent<Student> pagStudent = new StudentService().findPage(currentpage, pagesize);request.getSession().setAttribute("page", pagStudent);System.out.println("我又回到了这个界面");System.out.println(pagStudent.toString());List<Student> list = pagStudent.getList();for (Student student : list) {System.out.println(student);}System.out.println(pagStudent.getPagsize());System.out.println(pagStudent.getList());response.sendRedirect(request.getContextPath() + "/StudentPaging.jsp");} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();request.getSession().setAttribute("msg", "分页展示数据错误");response.sendRedirect(request.getContextPath() + "/msg.jsp");}}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doGet(request, response);}}

第五步：创建一个Servlet包，里边包含两个方法

package com.qf.service;import java.sql.SQLException;import java.util.List;import com.qf.dao.PagDao;import com.qf.javabean.PagStudent;import com.qf.javabean.Student;public class StudentService {public com.qf.javabean.PagStudent<Student> findPage(int currentpage, int pagesize) throws SQLException {PagDao dao= new PagDao();int totalcount= dao.findcount();//调用两个方法    List<Student> list=dao.findListPage(currentpage,pagesize);//return new PagStudent<Student>(currentpage,pagesize,totalcount,list);}}

第六步：连接数据库的Dao，里边执行SQL语句

package com.qf.dao;import java.sql.Connection;import java.sql.SQLException;import java.util.List;import org.apache.commons.dbutils.QueryRunner;import org.apache.commons.dbutils.handlers.BeanListHandler;import org.apache.commons.dbutils.handlers.ScalarHandler;import com.qf.javabean.Student;import com.qf.utils.DataSourceUtiles;public class PagDao {public int findcount() throws SQLException {// TODO Auto-generated method stubQueryRunner runner= new QueryRunner();String sql = "select count(*) from student;";Connection conn = DataSourceUtiles.getConnection();Object query = runner.query(conn,sql,new ScalarHandler());//DataSourceUtiles.close(conn);System.out.println("数据库可以走到聚合函数");return ((Long)query).intValue();//此处的query为long型，转化}public List<Student> findListPage(int currentpage, int pagesize) throws SQLException {// TODO Auto-generated method stubQueryRunner runner= new QueryRunner();String sql="select *from student limit ?,?;";Connection connection = DataSourceUtiles.getConnection();List<Student> list = runner.query(connection, sql, new BeanListHandler<Student>(Student.class), (currentpage-1)*pagesize,pagesize);System.out.println("这一个数据也可以走到的");for (Student student : list) {System.out.println(student);}//DataSourceUtiles.close(connection);return list;}}

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