<jsp:forward page="details.jsp"/>报错
<%--  
     Document   : vote
     Created on : 2011-9-15, 15:56:46
     Author     : Administrator
--%>
<%@page contentType="text/html" pageEncoding="GB2312"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
<%@page language="java" import="java.sql.*"%>
<jsp:useBean id="connDbBean" scope="page" class="vote.VoteConn"/>
<%
   String rb = request.getParameter("type");
   if(rb != null && rb != "") {
     String sql = "update vote Set c_num=c_num+1 where id=" + rb;
     connDbBean.executeUpdate( sql );
   }
%>
<jsp:forward page="details.jsp"/>
报错:
HTTP Status 500 -  
--------------------------------------------
type Exception report
message  
description 
The server encountered an internal error () that prevented it from fulfilling this request.exception  
org.apache.jasper.JasperException: An exception occurred processing JSP page /vote.jsp at line 20
17:     connDbBean.executeUpdate( sql );
18:   }
19: %>
20: <jsp:forward page="details.jsp"/>
Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handle
JspException(JspServletWrapper.java:510)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:401)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
root cause  
org.apache.jasper.JasperException: 
An exception occurred processing JSP page /details.jsp at line 28
25: <%
26:    // 获取总票数
27:    ResultSet tmpRs = connDbBean.executeQuery("select sum(c_num) As totalnum from vote");
28:    tmpRs.next();
29:    tot_num = tmpRs.getInt("totalnum");
30:    tmpRs.close();
31:    ResultSet rs = connDbBean.executeQuery("select * from vote");
Stacktrace:
	org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:510)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:419)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
	org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)
	org.apache.jasper.runtime.PageContextImpl.doForward(PageContextImpl.java:706)
	org.apache.jasper.runtime.PageContextImpl.forward(PageContextImpl.java:677)
	org.apache.jsp.vote_jsp._jspService(vote_jsp.java:79)
	org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
	org.apache.jasper.servlet.JspServlet.serviceJspFile(