这是看韩顺平老师的servlet视频,自己动手写的,楼主看韩顺平老师的servlet是2006制作的,用的是sql server数据库,自己又用的是oracle数据库,所以怕有的同学遇到同样的问题,不知道去哪参考oracle,所以想写一写oracle版本的servler分页技术!在写代码之前,首先要弄明白分页算法:
四个变量,int pageSize:每页显示多少条记录.int pageNow:希望显示第几页.int pageCount:一共有多少页,int rowCount:一共有多少条记录! 其中,pageSize是指定的,pageNow是用户或者默认的,就是现在显示第几条,rowCount是从表中查询得到的,pageCount是表示页数,有多少页,需要计算,计算的算法是:
if(rowCount%pageSize == 0) { pageCount = rowCount/pageSize; } else { pageCount = rowCount/pageSize + 1; }
从数据库中查询出记录总数的slq语句:
select count(*) from users
分页时候遇到一个问题,如果第十一条数据到第二十条数据中,缺少一条,也就是说,记录顺序不是连续的,是断开的,怎么查询出连续的记录?sql语句如下:
rs = st.executeQuery("select * from(select t.*, rownum rn from(select * from users order by userid) t where rownum <=" + pageNow*pageSize+ ") where rn >=" + ((pageNow-1)*pageSize+1) +"");
在不断的调试代码过程中,还顺便引入了css和加入动态图片,效果如图,
java代码:
package cn.com.shizongger; import javax.servlet.*; import javax.servlet.http.*; import java.sql.*; import java.io.*; public class FenYe extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse res){ int pageSize = 5; //每页显示5条记录 int pageNow = 1; //希望显示第几页,默认第一页 int pageCount = 0; //总数页,用总记录数除每页显示多少条记录 int rowCount = 0; //总记录数 //从数据库中计算出总记录数 Connection ct = null; Statement st = null; ResultSet rs = null; res.setContentType("text/html;charset=gbk"); //从url中获取要现实的页数 String pageStr = req.getParameter("pageNow"); try{ PrintWriter out = res.getWriter(); //1.加载驱动 Class.forName("oracle.jdbc.driver.OracleDriver"); //2.得到链接 ct = DriverManager.getConnection("jdbc:oracle:thin:@127.0.0.1:1521:orcl", "scott", "Shizongger_5476"); //获取状态 st = ct.createStatement(); //从数据库中获取总记录数 rs = st.executeQuery("select count(*) from users"); if(rs.next()) { rowCount = rs.getInt(1); if(rowCount%pageSize == 0) { pageCount = rowCount/pageSize; } else { pageCount = rowCount/pageSize + 1; } } if(pageStr != null) { //从字符串中转整型 pageNow = Integer.parseInt(pageStr); if(pageNow > pageCount) { pageNow = pageCount; } else if(pageNow < 1) { pageNow = 1; } } //从数据库中查询记录 //rs = st.executeQuery("select * from users where userid between " + ((pageNow-1)*pageSize+1) // + " and " + pageNow*pageSize + " order by userid"); rs = st.executeQuery("select * from(select t.*, rownum rn from(select * from users order by userid) t where rownum <=" + pageNow*pageSize+ ") where rn >=" + ((pageNow-1)*pageSize+1) +""); System.out.println(((pageNow-1)*pageSize+1) + " " + (pageNow*pageSize)); out.println("<html>\n<head>"); //为页面添加css样式 out.println("<link rel=\"stylesheet\" type=\"text/css\" href=\"mycss.css\" />"); out.println("</head>\n<body background=hudie.gif><center>"); out.println("<h1>恭喜,你已经成功登录系统</h1>"); out.println("总记录:" + rowCount); out.println("<table>"); out.println("<tr><th>用户ID</th><th>用户名</th><th>密码</th><th>Email</th><th>等级</th></tr>"); while(rs.next()) { out.println("<tr>"); out.println("<td>" + rs.getInt(1) + "</td>"); out.println("<td>" + rs.getString(2) + "</td>"); out.println("<td>" + rs.getString(3) + "</td>"); out.println("<td>" + rs.getString(4) + "</td>"); out.println("<td>" + rs.getInt(5) + "</td>"); out.println("</tr>"); } out.println("</table>"); //显示首页 out.println("<a href=fenye?pageNow=" + 1 + " >" + "首页" + "</a>"); //显示上一页 out.println("<a href=fenye?pageNow=" + (pageNow-1) + " >" + "上一页" + "</a>"); //显示页数 int start = (int)(pageNow/10)*10 + 1; for(int i = start; i <= start+9; i++) { if(i >= 1 && i <= pageCount) { if(i != pageNow) { out.println("<a href=fenye?pageNow=" + i + " >" + i + "</a>"); } else { out.println("<a class=style1 href=fenye?pageNow=" + i + " >" + i + "</a>"); } } } //显示上一页 out.println("<a href=fenye?pageNow=" + (pageNow+1) + " >" + "下一页" + "</a>"); //尾页 out.println("<a href=fenye?pageNow=" + pageCount + " >" + "尾页" + "</a>"); out.println("</center>\n</body>\n</html>"); } catch(Exception ex) { ex.printStackTrace(); } } @Override protected void doPost(HttpServletRequest req, HttpServletResponse res) { this.doGet(req, res); } }
外部css代码:
table { width:550px; } a:link{ text-decoration:none; color:blue; } a:visited{ text-decoration:line-through; color:blue; } a:hover{ text-decoration:underline; color:red; } a:active{ text-decoration:overline; color:red; } h1{ font-size:24px; color:red; } .style1{ font-size:22px; }