EXT JS

Hi, i created a grid panel with a check box in each row and i retrieved data from database and set the value for grid panel. i set a value for check box also but when i read the value of the check box it displays null. how to set the value for the check box from mysql in extjs grid. below is my coding.

<%@page contentType="text/html" pageEncoding="UTF-8"%> <%@page import = "java.sql.*"%>

    <%
                        try {
                            Class.forName("com.mysql.jdbc.Driver");
                            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/BankDb", "root", "ims");
                            Statement stmt = con.createStatement();
                            String query = "select AccountNumber,AccountNumber,Fullname,AccountType,MobileNumber,Email from details";
                            ResultSet rs = stmt.executeQuery(query);
                            int i;
                            String gridData = "";
                            rs.last();
                            int numrows = rs.getRow();
                            rs.first();
                            rs.beforeFirst();

                            for (i = 0; i <= numrows; i++)
                                {
                                 while (rs.next()) 
                                  {
                                    if (gridData.equals("")) 
                                    {
                                        gridData = "['" + rs.getString(1) + "','" + rs.getString(2) + "','" + rs.getString(3) + "','" + rs.getString(4) + "','" + rs.getString(5) + "','"+rs.getString(6)+"']";
                                    } 
                                    else 
                                    {
                                        gridData += ",['" + rs.getString(1) + "','" + rs.getString(2) + "','" + rs.getString(3) + "','" + rs.getString(4) + "','" + rs.getString(5) + "','"+rs.getString(6)+"']";
                                    }
                                 }
                                }


                           %>

<% con.close(); } catch (Exception e) { out.print(e); } %>