我想实现一个很简单的投票功能,但每次提示while(rs.next())这里有错.由于不能完成编译,我用System.out.println()也看不到执行情况,麻烦一下.谢谢!部分代码如下:
<%@ page contentType="text/html;charset=GBK" %>
<%@ page language="java" import="java.sql.*"%>
<jsp:useBean id="vote" scope="page" class="voteConn.VoteConn"/>
<html>
<head>
<title>网上调查表</title>
</head>
<%!
ResultSet rs=null;
%>
<%
try{
rs = vote.executeQuery("select * from vote");
System.out.println(rs==null);
}catch(Exception ex){
System.out.println("连接数据库时异常");
}
%>
<body bgcolor="#FFCCCC">
<center>
<font face="隶书" size="6">调查问卷,请您投票：</font><br>
<font face="隶书" size="5">您认为哪种技术最好（单选）</font><p>
<Table width="114" border bgcolor="#FFFFCC">
<form action="vote.jsp">
<%while(rs.next()){%>
}
<TR><TD>
<input type="radio" name="type" value=<%=rs.getString("id")%>>
<%=rs.getString("content")%>
</TD></TR>
<%
}
rs.close();
%>
<TR align="center"><TD><Input type="submit" value="投票"></TD></TR>
</form>
</Table>
<br><A href="view.jsp">查看投票</A>
</center>
</body>
</html>
<%@ page contentType="text/html;charset=GBK" %>
<%@ page language="java" import="java.sql.*"%>
<jsp:useBean id="vote" scope="page" class="voteConn.VoteConn"/>
<html>
<head>
<title>网上调查表</title>
</head>
<%!
ResultSet rs=null;
%>
<%
try{
rs = vote.executeQuery("select * from vote");
System.out.println(rs==null);
}catch(Exception ex){
System.out.println("连接数据库时异常");
}
%>
<body bgcolor="#FFCCCC">
<center>
<font face="隶书" size="6">调查问卷,请您投票：</font><br>
<font face="隶书" size="5">您认为哪种技术最好（单选）</font><p>
<Table width="114" border bgcolor="#FFFFCC">
<form action="vote.jsp">
<%while(rs.next()){%>
}
<TR><TD>
<input type="radio" name="type" value=<%=rs.getString("id")%>>
<%=rs.getString("content")%>
</TD></TR>
<%
}
rs.close();
%>
<TR align="center"><TD><Input type="submit" value="投票"></TD></TR>
</form>
</Table>
<br><A href="view.jsp">查看投票</A>
</center>
</body>
</html>
}
为:
while(rs.next())
{%>
org.apache.jasper.JasperException: An exception occurred processing JSP page /chap.jsp at line 2724: <form action="vote.jsp">
25: <%
26:
27: while(rs.next())
28:
29: {%>
30:
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:524)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:435)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause java.lang.NullPointerException
org.apache.jsp.chap_jsp._jspService(chap_jsp.java:91)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:393)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:320)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:266)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)