分页显示解决Result set type is TYPE_FORWARD_ONLY

最新推荐文章于 2023-11-15 10:25:46 发布

原创最新推荐文章于 2023-11-15 10:25:46 发布 · 5.3k 阅读

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#string #input #import #action #border #html

本文介绍了一种在JSP页面中实现数据库查询结果分页显示的方法。通过将查询结果存储在Result对象中并计算总页数，实现了动态跳转及数据显示。文章还解决了Resultset类型为TYPE_FORWARD_ONLY时使用last()方法导致的错误。

jsp页面中，当进行数据库查询时，数据过多时，可用分页显示。常用的方法是把所有结果放到Result对象当中，然后用Result.last（）把指针移到未尾，然后对记录的数量用Result.getRow（）得到。完了以后就可进行分页设计。当指定的页码显示记录数为Size，总的记录有Count条，则总的页码数为N=（Size+Count-1）/Size.

整个页面如下：

<%@ page language="java" contentType="text/html; charset=gb2312" pageEncoding="gb2312"
%>
<%@ page import="java.sql.*" %>
<%@ page import="java.util.*" %>
<%@ page import="java.text.*" %>
<%@ page import="java.util.Date" %>
<jsp:useBean id="ConnectBean" scope="page" class="dbpackage.conn"></jsp:useBean>
<%if(session.getAttribute("logined").equals("yes")){
%>
<% int intPageSize;
int intRowCount=0;
int intPageCount;
int intPage;
String strPage;
intPageSize = 1;
strPage = request.getParameter("page");
if(strPage==null)
  intPage=1;
else
{
  intPage=Integer.parseInt(strPage);
  if(intPage<1)intPage=1;
}

String username=(String)session.getAttribute("username").toString();
String sql = "select * from subject where subject_teacher ='"+username+"'";
ResultSet rs=null;
rs = ConnectBean.executeQuery(sql);
//try
//{
rs.last();

intRowCount = rs.getRow();
//}
//catch(java.lang.Exception ex)
//{
//System.out.print(ex.getMessage());
//}

intPageCount = (intRowCount+intPageSize-1)/intPageSize;
if(intPage > intPageCount)intPage = intPageCount;

%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>登录页面</title>
</head>
<body>
  <p align="center"><img width="540" height="150" border="0" src="../image/222.JPG"></p><div align="center"><div align="left">               
  <%=session.getAttribute("username") %>老师<br></div>
  </div>
   <div align="right"><form method="post" action="add_subject.jsp">                                                                               
    <input type="submit" name="add_subject" value="添加题目"></form></div><div align="right"><form method="post" action="../logout.jsp">
    <input type="submit" name="logout" value="注销"></form></div>
  <form method="post" action="teacher_manage.jsp">
   第<%=intPage%>页共<%=intPageCount%>页
   <%if(intPage <intPageCount){%>
    <a href = "teacher_manage.jsp?page=<%=intPage+1%>">下一页</a>
   <%}%>

   <%if(intPage > 1){%>
    <a href = "teacher_manage.jsp?page=<%=intPage-1%>">上一页</a>
   <%}%>
   转到第：<input type="text" name = "page" size = "8">页
   <span><input type = "submit" name ="1"vlaue = "GO" ></span>
  </form>
  <table width="800" border="2">
   <tbody >
   <tr>
    <td width="50"align="center">序号</td>
    <td width="50"align="center">状态</td>
    <td width="250" align="center">题目</td>
    <td width="50" align="center">老师</td>
    <td width="50" align="center">选题</td>
    <td width="150" align="center">内容</td>
    <td width="100" align="center">操作</td>
   </tr>
   <%
   if( intPageCount > 0)
   {
    rs.absolute((intPage-1)*intPageSize+1);
    int xuhao=0;
    int i=0;
    while(i<intPageSize&&!rs.isAfterLast())
    {

    int subject_id = rs.getInt("subject_id");
    String subject_name = rs.getString("subject_name");
    String subject_teacher = rs.getString("subject_teacher");
    String subject_student = "";
    subject_student=rs.getString("subject_student");
    rs.next();
    i++;
   %>
  <tr>
   <td width="50"align="center"><%=Integer.toString(xuhao++)%></td>
   <td width="50"align="center">
   <%if(!(subject_student==null))
   { %>
    <input type="radio" checked="true" value="1" >
   <%}
   else{%>
    <input type="radio" value="1" >
   <%}%></td>
   <td width="250" align="center"><%=subject_name%></td>
   <td width="50" align="center"><%=subject_teacher%></td>
   <td width="50" align="center"><%=subject_student%><%=subject_id%></td>
   <td width="150" align="center"><%=subject_name%></td>
   <td width="100" align="center"><a href="change.jsp?subject_id=<%=subject_id%>">修改</a> _fcksavedurl=""change.jsp?subject_id=<%=subject_id%>">修改</a>" _fcksavedurl=""change.jsp?subject_id=<%=subject_id%>">修改</a>" <a href="delete.jsp?subject_id=<%=subject_id%>">删除</a></td>
   </tr>
   <%} %>
  </tbody></table>
</body>
</html>
<%}}%>

结果在控制台显示Result set type is TYPE_FORWARD_ONLY的错误信息。

查看数据库连接的Bean：dbpackage.conn，里面对Statement对象的创建是默认方。这样在返回的 Statement 对象创建的结果集在默认情况下类型为 TYPE_FORWARD_ONLY，并带有 CONCUR_READ_ONLY 并发级别。因此不允许用last（）方法，一旦调用这个方法就会出在上述错误。

对statement创建修改如下：Statement stmt = connect.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);

再运行程序，分页成功实现。