好心人帮帮忙解决一下数据库连接的问题!急!急!

请高手们帮我看看这个问题，搞了好几次都出现错误（已经加载了sqlserver的3个驱动文件）,源程序和出现的错误提示如下:package shop;
import java.sql.*;public class DBConnectBean {
  public static Connection getSqlserverConn()
  {
   Connection conn=null;
   String url="com.microsoft.jdbc.sqlserver.SQLServerDriver";
   String sqldriver="jdbc:microsoft:sqlserver://localhost:1433;DataBaseName=jspdev";
  try {
    Class.forName(url);
    conn=DriverManager.getConnection(sqldriver,"sa","");
    conn.setCatalog("jspdev");
  }
  catch (Exception ex) {
    ex.printStackTrace();  }
    return conn;  }
}
---------------------------------------------------
<%@ page contentType="text/html; charset=GBK" import="java.sql.*"%>
<html>
<head>
<title>
logincheck.jsp
</title>
</head>
<body bgcolor="#ffffff">
<jsp:useBean id="dbconn" class="shop.DBConnectBean" scope="page"/>
<%
//获得请求参数
 String name=request.getParameter("username");
 String password=request.getParameter("userpassword");
 //连接数据库
  dbconn.getSqlserverConn();
  String usersql="select * from users where name='"+name+"'and password='"+password+"'";
  Connection con=null;
   Statement stmt=con.createStatement();
   ResultSet result=stmt.executeQuery(usersql);
   if(result.next())
  {
    %>
 欢迎你，<%=name%>
  <%}%>
</body>
</html>
------------------------------------------------
java.lang.NullPointerExceptionjava.lang.NullPointerException at org.apache.jsp.logincheck$jsp._jspService(logincheck$jsp.java:96) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:201) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:381) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:473) at javax.servlet.http.HttpServlet.service(HttpServlet.java:853) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.CertificatesValve.invoke(CertificatesValve.java:246) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174) at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472) at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943) at org.apache.catalina.connector.http.HttpProcessor.process(HttpProcessor.java:1027) at org.apache.catalina.connector.http.HttpProcessor.run(HttpProcessor.java:1125) at java.lang.Thread.run(Thread.java:536)