请解决一下这个JSP有关问题

请各位高手解决一下这个JSP问题
这段代码,我执行时出错如下;
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:358)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
root cause
java.lang.NullPointerException
bean.jdbcBean.closeDB(jdbcBean.java:41)
org.apache.jsp.checkout_jsp._jspService(checkout_jsp.java:172)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
note The full stack trace of the root cause is available in the Tomcat logs.
源码:
<%@ page contentType= "text/html; charset=gb2312 " language= "java " import= "java.sql.* " errorPage= " " %>
<!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> 网上碟店:碟碟不休 </title>
</head>
<body>
<%@ include file= "header.jsp "%>
<table width= "800 " height= "400 " border= "1 " align= "center ">
<tr>
<td> <%
Vector buylist = (Vector)session.getValue( "shopcar ");
if(buylist==null||buylist.size() <1)
{
%>
<jsp:forward page= "mydisk.jsp "> </jsp:forward>
<%}
String userid = (String)session.getValue( "uid ");
float pricenum =0;
for(int i=0;i <buylist.size();i++)
{
Disk disk = (Disk)buylist.elementAt(i);
pricenum = pricenum + disk.getBuynum()*disk.getPrice();
}

jdbcBean diskBean1=new jdbcBean();
String sql1= "INSERT INTO myorder(user_id, price_num, order_time) VALUES( ' "+userid+ " ', "+pricenum+ ", ' "+current_time+ " ') ";
int m=diskBean1.executeUpdate(sql1) ;
diskBean1.closeDB();
jdbcBean diskBean2=new jdbcBean();
String sql2= "SELECT order_id FROM myorder WHERE order_id= ' "+userid+ " ' AND order_time= ' "+current_time+ " ' ";
ResultSet rs=diskBean2.executeQuery(sql2) ;
rs.next();
String orderid = rs.getString( "order_id ");
diskBean2.closeDB();

for(int j=0; j <buylist.size(); j++)

{
Disk disk = (Disk)buylist.elementAt(j);
jdbcBean diskBean3=new jdbcBean();
String sql3= "INSERT INTO orderitem(order_id, sno, disk_num) VALUES( ' "+orderid+ " ', ' "+disk.getSno()+ " ', ' "+disk.getBuynum()+ " ') ";
int mm=diskBean3.executeUpdate(sql3);
diskBean3.closeDB();
}
%> </td>
</tr>
</table>
<%@ include file= "footer.jsp "%>
</body>
</html>

我已在header.jsp中包含了所需的包 <%@ page import= "java.io.* "%>
<%@ page import= "java.util.* "%>
<%@ page import= "java.sql.* "%>
<%@ page import= "java.text.* "%>
<%@ page import= "bean.* "%>
上面代码在然出错,但是它还是能在数据表myorder中插入了数据,期待各位的帮助!!

[解决办法]
空指常,NullPointerException
看看你的closeDB方法.接是否打?
逐步一下你的句,看有哪些量是有被值的.
[解决办法]
这个是你的 ResultSet rs; rs你没用过或是你已经关了 rs.close()多关了
[解决办法]
一步步的调试,不要一下全写出来
我的异常网推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.myexception.cn/java-web/317.html

请解决一下这个JSP有关问题

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