variable rs might not have been initialized

<%@ page contentType="text/html; charset=GBK" %>
<%@ page import="java.sql.*" %>
<html>
<head>
<title>
jg
</title>
</head>
<body bgcolor="#ffc7c7">
<h1>
JBuilder Generated JSP
</h1>
<form method="post" action="jg.jsp">
<br><br></form><%
String SQL="";
String key=request.getParameter("key");
String way=request.getParameter("type");
if(way.trim().equals("0"))
{
  SQL="select * from book where bookno like'%"+key+"%'";
}
if(way.trim().equals("1"))
{
  SQL="select * from book where bookname like'%"+key+"%'";
}
if(way.trim().equals("2"))
{
  SQL="select * from book where kindno like'%"+key+"%'";
}
if(way.trim().equals("3"))
{
  SQL="select * from book where author like'%"+key+"%'";
}
if(way.trim().equals("4"))
{
  SQL="select * from book where cbs like'%"+key+"%'";
}
if(way.trim().equals("5"))
{
  SQL="select * from book where memo like'%"+key+"%'";
}%><% out.println("<div align='center'><font size='5' color='red'><b>符合条件的书如下:</b></font></div>");
out.println("<br>");
out.println("<table width='770' align='center'bgcolor=cccccc>");
out.println("<tr>") ;
out.println("<td width='100'><b>书号</b></td>");
out.println("<td width='100'><b>书名</b></td>");
out.println("<td width='100'><b>图书类别</b></td>");
out.println("<td width='100'><b>作者</b></td>");
out.println("<td width='100'><b>价格</b></td>");
out.println("<td width='100'><b>图书数量</b></td>");
out.println("<td width='100'><b>出版社</b></td>");
out.println("<td width='100'><b>备注</b></td>");
out.println("</tr>") ;
out.println("</table>");
%>
<%
Connection con;
Statement st;
ResultSet rs;
try{
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:library1");
st=con.createStatement();
rs=st.executeQuery(SQL);
}
catch(Exception ex)
{
  ex.printStackTrace();
}int searchnum=0;
try
{
  while(rs.next())这里出错
  {String bookno,bookname,kindno,author,cbs,memo;
   int price,number;
   bookno=new String(rs.getString("bookno")) ;
   bookname=new String(rs.getString("bookname")) ;
   kindno=new String(rs.getString("kindno")) ;
   author=new String(rs.getString("author")) ;
   price=rs.getInt("price") ;
   number=rs.getInt("number") ;
   cbs=new String(rs.getString("cbs") ) ;
   memo=new String(rs.getString("memo") ) ;   //输出从数据库读出的结果
   out.println("<table width='770'align='center'>");
   out.println("<tr>");
   out.println("<td width='100'>"+bookno+"</td>");
   out.println("<td width='100'>"+bookname+"</td>");
   out.println("<td width='100'>"+kindno+"</td>");
   out.println("<td width='100'>"+author+"</td>");
   out.println("<td width='100'>"+price+"</td>");
   out.println("<td width='100'>"+number+"</td>");
   out.println("<td width='100'>"+cbs+"</td>");
   out.println("<td width='100'>"+memo+"</td>");
   out.println("<td width='100'>");
   out.println("</tr>");
   out.println("</table>");
   searchnum++;
   }
   rs.close() ;
   out.println("<br>");
   out.println("<table width='770' align='cebter'>");
   out.println("<tr>");
   out.println("<td>");
   out.println("共搜索到<b><font color=red>"+searchnum+"</font></b>条记录.");
   out.println("</td>");
   out.println("</tr>");
   out.println("</table>");}
catch(Exception ex)
{
  ex.printStackTrace();
}
 %></body>
</html>