jsp连接sybase数据库出错

我用jsp连接sybase出错。请帮忙看看sybase的jdbc连接时下载了一个jconn2.jar，并把它放到tomcat/common/lib下。程序如下：<%@page contentType="text/html;charset=gb2312" pageEncoding="gb2312" language="java" import="java.sql.*"%>
<%
 Class.forName("com.sybase.jdbc.SybDriver").newInstance(); 
 String url="jdbc:sybase:Tds:111.222.333.444:4100/dbname"; 
 String user="sa";
 String password="123456";
 Connection conn=DriverManager.getConnection(url,user,password); 
%><table width="600" border="1" cellpadding="5" cellspacing="0" bordercolorlight="#999999" bordercolordark="#FFFFFF" align="center">
  <tr bgcolor="#BFCCDF">  
    <td width="120" height="23"><div align="center"><b>借还日志</b></div></td>
    <td width="580" colspan="2" height="23"><div align="center"><b>显示所有数据</b></div></td>            
  </tr>         
<%
   Statement stmt = conn.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
   String sqlstr = "select top 10 * from circul.circulog_A";
   ResultSet rs = stmt.executeQuery(sqlstr);
   while(rs.next()) 
   {
    }
%>
错误提示是：
org.apache.jasper.JasperException: Exception in JSP: /test/test.jsp:3
1: <%@page contentType="text/html;charset=gb2312" pageEncoding="gb2312" language="java" import="java.sql.*"%>
2: <%
3: Class.forName("com.sybase.jdbc.SybDriver").newInstance(); 
4: String url="jdbc:sybase:Tds:111.222.333.444:4100/dbname"; 
5: String user="sa";
6: String password="123456";
7: Connection conn=DriverManager.getConnection(url,user,password); Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:467)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:371)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause javax.servlet.ServletException: com.sybase.jdbc.SybDriver
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:846)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:779)
org.apache.jsp.test.test_jsp._jspService(test_jsp.java:89)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)