又是Null?该如何解决

package com.fuyou.servlet;import java.io.IOException;import java.sql.ResultSet;import java.sql.SQLException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.fuyou.util.DBConnection;import com.fuyou.util.mvconnection;public class loginservlet extends HttpServlet {    private DBConnection dbc = new DBConnection();    private static final long serialVersionUID = -3265621922663327137L;    public loginservlet() {    }    public void destroy() {        super.destroy();    }    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doPost(request, response);    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        String username = request.getParameter("username");        String password = request.getParameter("password");        String conformPswd = "";        String sql = "select * from user where username='" + username + "'";        ResultSet rs = null;        mvconnection mvc = new mvconnection();        if (mvc != null) {            rs = mvc.getResultSet(sql);        } else {            return;        }        if (rs != null) {            try {                if (rs.getString("password") != null) {                    conformPswd = rs.getString("PASSWORD");                }                return;            } catch (SQLException e) {                e.printStackTrace();            } finally {                this.dbc.closeResultSet(rs);            }        }        if (password.equals(conformPswd)) {        }    }    public void init() throws ServletException {    }}

rs.hasNext()
------解决方案--------------------
嘿嘿，没法了，换驱动吧。
------解决方案--------------------
你的这段程序好像不怎么对：
       if (rs != null) {