分页操作
Posted GEORES
tags:
篇首语：本文由小常识网(cha138.com)小编为大家整理，主要介绍了分页操作相关的知识，希望对你有一定的参考价值。
进行网页开发，那么就少不了分页查询。分页查询在mysql中是最方便的，使用mysql的关键字LIMIT(mysql独有)，即可进行分页查询。如下是mysql的分页查询的sql语句：
SELECT * FROM hero LIMIT ?, ? # 第一个?表示的是从那条数据开始查询 # 第二个?表示的是每次查询的数据的条数
而在Oracle中也有一个方言，专门用来Oracle数据库的分页查询，关键字为：ROWNUM 和 row_number()
下面使用mysql演示分页：
jsp页面：
<%@ 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>分页操作</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 href="table.css" rel="stylesheet" type="text/css"> </head> <body> <div align="center"><h1 style="color: #000000; align:center">演示分页查询</h1></div> <table cellpadding="1" border="1" cellspacing="0" bordercolor="black" align="center"> <tr class="tab-2"> <td>编号</td> <td>英雄名字</td> <td>英雄Job</td> <td>英雄上司编号</td> <td>英雄雇佣日期</td> <td>英雄薪水</td> <td>英雄奖金</td> <td>英雄类型</td> </tr> <%-- <c:if test="${null ne heros }"> --%> <c:forEach items="${heros }" var="hero"> <tr class="tab-5"> <td>${hero.herono }</td> <td>${hero.heroname }</td> <td>${hero.herojob }</td> <td>${hero.heromgr }</td> <td>${hero.herohiredate }</td> <td>${hero.herosal }</td> <td>${hero.herocomm }</td> <td>${hero.herotype }</td> </tr> </c:forEach> <%-- </c:if> --%> </table><br/><br/> <div align="center"> <c:if test="${num-1 > 0 }"> <a href="<c:url value=\'/SplitServlet\'/>?method=splitenum&num=${num-1}">上一页</a> <a href="<c:url value=\'/SplitServlet\'/>?method=splitenum&num=${num-1}">第${num-1 }页</a> </c:if> <a href="<c:url value=\'/SplitServlet\'/>?method=splitenum&num=${num}">第${num }页</a> <c:if test="${num+1 <= all }"> <a href="<c:url value=\'/SplitServlet\'/>?method=splitenum&num=${num+1}">第${num+1 }页</a> <a href="<c:url value=\'/SplitServlet\'/>?method=splitenum&num=${num+1}">下一页</a> </c:if> <a href="<c:url value=\'/SplitServlet\'/>?method=splitenum&num=1">刷新</a> <font color="red" size="5px">总共 ${all } 页</font> </div> </body> </html>
dao：
package cn.geore.splitpage;
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 priv.geore.toolutils.jdbc.FirmQueRunner;
public class SplitPageDao {
QueryRunner runner = new FirmQueRunner();
/**
* 查询每页的数据
* @param page
* @param count
* @return
* @throws SQLException
*/
public List<Hero> findHero(int page, int count) throws SQLException {
String sql = "SELECT * FROM hero LIMIT ?,?";
Object[] params = {(page-1)*4,count};
return (List<Hero>) runner.query(sql, new BeanListHandler<Hero>(Hero.class), params);
}
/**
* 查询页数
* @return
* @throws SQLException
*/
public Number count() throws SQLException {
String sql = "SELECT count(*) FROM hero";
return runner.query(sql, new ScalarHandler<Number>());
}
}
servlet：
package cn.geore.splitpage;
import java.io.IOException;
import java.sql.SQLException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import priv.geore.toolutils.web.FirmHttpServlet;
public class SplitServlet extends FirmHttpServlet {
SplitPageDao dao = new SplitPageDao();
/**
* 分页查找数据
* @param request
* @param response
* @return
* @throws ServletException
* @throws IOException
*/
public String splitenum(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
int num = Integer.valueOf(request.getParameter("num"));
List<Hero> heros = null;
int all = 0;
try {
heros = dao.findHero(num, 4);
all = (int) Math.floor(dao.count().intValue() / 4.0);
} catch (SQLException e) {
throw new RuntimeException(e);
}
request.setAttribute("heros", heros);
request.setAttribute("num", num);
request.setAttribute("all", all);
return "f:/index.jsp";
}
}
运行截图：
以上是关于分页操作的主要内容，如果未能解决你的问题，请参考以下文章
FragmentStatePagerAdapter 视图分页器片段在活动重新创建后不显示