刚学jsp,分页技术请高手指教!
每次都提示空指针,请高手指教
<%!
ResultSet rs = null;
ResultSet rsTmp = null;
String sql = "";
int PageSize = 13;
int Page = 1;
int totalPage = 1;
String str = "";
Hashtable ht = new Hashtable(); // Hashtable用于存储班级代号和班级信息之间的对应关系
public String ShowOnePage(ResultSet rs, int Page, int PageSize) {
str = "";
// 先将记录指针定位到相应的位置
try {
rs.absolute( (Page-1) * PageSize + 1);
}catch(SQLException e) {
}
int iPage=1;
for( iPage=1; iPage<=PageSize; iPage++) {
str += showOneRecord(rs,Page);
try {
if(!rs.next()) break;
}catch(Exception e) {}
}
return str;
}
// 显示单行记录子模块, 由于要将当前页码传递到后面的修改和删除页面,
// 因此,下面的shosOneRecord方法多了第二个参数
public String showOneRecord( ResultSet rs, int page ) {
String tt = "";
int endindex = 16; // 在默认情况下显示题目标题中的前12个汉字字符
String tmp = "";
int tmpselectid = 0;
int tmpquestionid = 0;
try {
tt += "<TR class=dbt4 align=middle>";
tmpquestionid = rs.getInt("questionid");
tt += "<TD>" + tmpquestionid + "</TD>";
tmpselectid = rs.getInt("selectid");
if(tmpselectid==1)
tt += "<TD>单选</TD>";
else if(tmpselectid==2)
tt += "<TD><font color=blue>多选</font></TD>";
tt += "<TD>" + (String)(ht.get(rs.getString("classid"))) + "</TD>";
tmp = rs.getString("qname");
if(tmp.length() < endindex)
endindex = tmp.length();
tt += "<TD align=left>" + tmp.substring(0,endindex) + "</TD>";
tt += "<TD><a href=javascript:openwin(" + tmpquestionid + ")>";
tt += "察看</a></TD>";
tt += "<TD><a href=questionchange.jsp?id=" + tmpquestionid + "&Page=" + page + ">修改</TD>";
tt += "<TD><a href=questiondel.jsp?id=" + tmpquestionid + "&Page=" + page + ">删除</TD>";
tt += "</TR>";
}catch(SQLException e) {}
return tt;
}
%>
<%
sql = "select * from test_classinfo";
try {
rs = smt.executeQuery( sql );
}catch(Exception e) {
out.println("访问课程信息数据出错!");
return;
}
if(!rs.next()) {
out.println("系统数据库中无课程信息数据!");
return;
}
do {
ht.put(rs.getString("classid"),rs.getString("classname"));
}while(rs.next());
sql = "select * from test_question_lib order by questionid";
try {
rs = smt.executeQuery( sql );
}catch(Exception e) {
out.println("访问题库信息出错!");
return;
}
%>
<html>
<head>
<title>试题库信息维护</title>
<link rel="stylesheet" href="../public/style.css">
<Script language="JavaScript">
//打开新窗口函数openwin
function openwin(id)
{
window.open('questiondetails.jsp?id='+id,'infoWin', 'height=400,width=600,scrollbars=yes,resizable=yes');
}
</Script>
</head>
<body class="ss">
<h2 ALIGN="CENTER">试题库信息维护</h2>
<hr>
<center>
<table class=dbt2 width=640 cellSpacing=1 cellPadding=3 border=0>
<tr class=dbt3 align=center>
<TH>题目编号</TH>
<TH>题型</TH>
<TH>课程名称</TH>
<TH width=200>题目简介</TH>
<TH>题目详细信息</TH>
<TH colspan=2>编辑操作</TH>
</TR>
<%
rsTmp = smt.executeQuery("select count(*) as mycount from test_question_lib");
rsTmp.next();
int totalrecord = rsTmp.getInt("mycount");
if(totalrecord % PageSize ==0) totalPage = totalrecord / PageSize; // 如果是当前页码的整数倍
else totalPage = (int) Math.floor( totalrecord / PageSize ) + 1; // 如果最后还空余一页
if(totalPage == 0) totalPage = 1;
rsTmp.close();
try {
if(request.getParameter("Page")==null || request.getParameter("Page").equals(""))
Page = 1;
else
Page = Integer.parseInt(request.getParameter("Page"));
// 捕获用户从浏览器地址拦直接输入类似于Page=sdfsdfsdf等非法信息所造成的异常
} catch(java.lang.NumberFormatException e) {
Page = 1;
}
if(Page < 1) Page = 1;
if(Page > totalPage) Page = totalPage;
out.println(ShowOnePage(rs, Page, PageSize));
%>
<TR class=dbt4 align=center>
<TD colspan=7><a href=questionadd.jsp>增加新题</a></TD>
</TR>
</table>
<form Action="questionmanager.jsp" Method="GET">
<%
if(Page != 1) {
out.println("<A HREF=questionmanager.jsp?Page=1>第一页</A>");
out.println("<A HREF=questionmanager.jsp?Page=" + (Page-1) + ">上一页</A>");
}
if(Page != totalPage) {
out.println("<A HREF=questionmanager.jsp?Page=" + (Page+1) + ">下一页</A>");
out.println("<A HREF=questionmanager.jsp?Page=" + totalPage + ">最后一页</A>");
}
rs.close();
%>
<p>输入页数:<input TYPE="TEXT" Name="Page" SIZE="3"> 页数:<font COLOR="Red"><%=Page%>/<%=totalPage%></font>
题目总数:<font color="red"><%=totalrecord%></font>
</p>
</form>
</center>
<hr>
</body>
</html>