jsp+javabean+oracle，求指出错误

package com.mingri.dbconn;

import java.sql.*;

public class DBResult {
public static Connection conn = null;{
try {
// Context ctx = new InitialContext();
// ctx = (Context) ctx.lookup("java:comp/env");
// DataSource ds = (DataSource) ctx.lookup("jdbc/mingri"); // 获取连接池对象

        String url="jdbc:oracle:thin:@192.168.1.101:1521:sale";
        String username="此处为用户名";
        String password="此处为密码";
       Class.forName("oracle.jdbc.driver.OracleDriver").newInstance();
       conn= DriverManager.getConnection(url, username, password);
       }catch(Exception e){
   }
}
/**
 * 用于获得执行SQL语句的ResultSet对象
 */
public ResultSet getResult(String sql) {
    try {
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery(sql);
        return rs;
    } catch (Exception e) {
    }
    return null;
}

/**
 * 用于执行SQL语句没有返回值
 */
public void doExecute(String sql) {
    try {
        Statement stmt = conn.createStatement();
        stmt.executeQuery(sql);
    } catch (Exception e) {
    }
}

/**
 * 用于获得执行SQL语句的PreparedStatement(预处理)对象
 */
public PreparedStatement getPreparedStatement(String sql) {
    try {
        PreparedStatement pstmt = conn.prepareStatement(sql);
        return pstmt;
    } catch (Exception e) {
    }
    return null;
}

}
我在jsp里调用总是连不上数据库，classes12.jar已放到lib下，在jsp页面用代码就能连上数据库，调用了javabean就不行了
<%@ page contentType="text/html;charset=gb2312" language="java"%>
<%@ page import="java.io.*,java.sql.*"%>


<%
request.setCharacterEncoding("gb2312");//对请求进行统一编码，能正常接收中文
String username=request.getParameter("username"); //接收表单中的username属性
String password=request.getParameter("password");//接收表单中的password属性

String sql="select * from users where"+" user_name='"+username+"' and password='"+password+"'";
ResultSet rs = rst.getResult(sql);
//session.setAttribute("isLog",new String("0"));//判断用户是否登录，当isLog的属性为0时，说明用户并没有登录
if(!rs.next())//结果集没有找到所要查找的行
{
out.println("alert(&#39;用户名或密码错误&#39;);&quot;+<br> &quot;parent.location.href=&#39;index.html&#39;;");
}
else
{ response.sendRedirect("main.html");//登录成功后转到系统主页面
}
%>
提示运行到13行if（rs.next）就不运行了，好像是未连接数据库导致

贴出报错信息呀，不然怎么知道错在哪

报错信息type Exception report

message An exception occurred processing JSP page /jxc-unfinished/login.jsp at line 13

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /jxc-unfinished/login.jsp at line 13

10: String sql="select * from users where"+" user_name='"+username+"' and password='"+password+"'";
11: ResultSet rs = rst.getResult(sql);
12: //session.setAttribute("isLog",new String("0"));//判断用户是否登录，当isLog的属性为0时，说明用户并没有登录
13: if(!rs.next())//结果集没有找到所要查找的行
14: {
15: out.println("alert(&#39;用户名或密码错误&#39;);&quot;+<br> 16: &quot;parent.location.href=&#39;index.html&#39;;");

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:521)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)

root cause

java.lang.NullPointerException
org.apache.jsp.jxc_002dunfinished.login_jsp._jspService(login_jsp.java:85)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)

note The full stack trace of the root cause is available in the Apache Tomcat/6.0.45 logs.

空指针 肯定是你rs为null，数据没有查到东西吧。你可以先判断下rs不为null再进行下一步操作