分页操作
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：
