jsp+JavaBEAN进行一个简单的登录数据库SQL

小弟初学JSP，想做一个简单登录，在JSP里面调用JAVABEAN,用的eclipse,在eclipse里面测试连接数据库能通过，在JSP不调用JAVABEAN连接数据库也能通过，但是2着结合就出问题了。下面是我的代码：
package opendb;
import java.sql.*;
public class opendb 
{
String sDBDriver="sun.jdbc.odbc.JdbcOdbcDriver";
String sConnStr="jdbc:odbc:ZHHAO";
Connection conn=null;
ResultSet rs=null;
public opendb()
{
try{
Class.forName(sDBDriver);
}
catch(java.lang.ClassNotFoundException e)
{
System.err.println("testJDBC():"+e.getMessage());
}
}
public ResultSet executeQuery(String testJDBC)
{
rs=null;
try{
conn=DriverManager.getConnection(sConnStr);
Statement stmt=conn.createStatement();
rs=stmt.executeQuery(testJDBC);

}
catch(SQLException ex)
{
System.err.println("aq.executeQuety:"+ex.getMessage());
}
return rs;
}
}
JSP代码：
<%@page language="java" import="java.sql.*"%>
<jsp:useBean id="RegisterBean" scope="page" class="opendb.opendb"/>
<%
String name1=request.getParameter("username");
String pwd1=request.getParameter("password");
String sql="select * from USER1 where username='"+name1+"' and password='"+pwd1+"'";
ResultSet rs=RegisterBean.executeQuery(sql);
if(rs.next())
{
rs.close();
session.putValue("username",name1);
%>
<script language=javacript>
window.location="info.jsp?str=haha""
</script>
<%
}
else{
rs.close();
session.putValue("login_message","Error on Login");
%>
<script language=javacript>
window.location="info.jsp?str=shibai""
</script>
<%
}
%>
</body>
</html>
错误显示：
type Exception reportmessage 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
org.apache.jsp.login_jsp._jspService(login_jsp.java:58)
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.