Re: I get a null pointer when running my applet

From:
"Justin" <justin.lottes@gmail.com>
Newsgroups:
comp.lang.java.help
Date:
16 Jan 2007 11:08:30 -0800
Message-ID:
<1168974510.249405.321940@a75g2000cwd.googlegroups.com>
Heres two of my classes. The first one is the applet class. It
creates a DataConnection class. The DataConnection class queries an
access database.

//**************
//Applet class
//**************

package consultviewer;

import java.awt.*;
import javax.swing.*;
import javax.swing.border.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class Main2 extends javax.swing.JApplet{

    JPanel jpan;
    Panel panel;

    int width = 794;

    public void init(){
    setSize(width, 500);
    }

    public Main2(){
    DataConnection dc = new DataConnection();

    DefaultListModel testing = dc.queryConnection("SELECT * FROM
newconsult;");
    System.out.println(testing);
    }
}

//**********
//DataConnection Class
//**********

package consultviewer;

import java.sql.*;
import javax.swing.DefaultListModel;
import javax.swing.*;

class DataConnection
       {

    String filename = "C:\\Documents and Settings\\Owner\\Consult.mdb";

    public DefaultListModel queryConnection(String sql){

        sql = sql.replace('"', '\'');
        Connection connection = null; // manages connection
        Statement statement = null; // query statement
        DefaultListModel returnedResults = null;
        // connect to database books and query database
        try {
            Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
            String database = "jdbc:odbc:Driver={Microsoft Access
Driver (*.mdb)};DBQ=";
            database+= filename.trim() + ";DriverID=22;READONLY=true}";
// add on to the end
            // establish connection to database
            connection = DriverManager.getConnection( database ,"","");

            // create Statement for querying database
            statement = connection.createStatement();
            // query database

            ResultSet resultSet = statement.executeQuery(sql);

            // process query results
            ResultSetMetaData metaData = resultSet.getMetaData();
            int numberOfColumns = metaData.getColumnCount();

            returnedResults = new DefaultListModel();

            while ( resultSet.next()){
                for ( int i = 1; i <= numberOfColumns; i++ ){
                    returnedResults.addElement(resultSet.getObject(i));
                }
            } // end while

        } // end try

        catch ( SQLException sqlException ) {
            sqlException.printStackTrace();
            System.exit( 1 );
        } // end catch
        catch ( ClassNotFoundException classNotFound ) {
            classNotFound.printStackTrace();
            System.exit( 1 );
        } // end catch
        finally // ensure statement and connection are closed properly
        {
            try {
                statement.close();
                connection.close();
            } // end try
            catch ( Exception exception ) {
        System.out.println("it failed here");
                exception.printStackTrace();
                System.exit( 1 );
            } // end catch
        } // end finally
        return returnedResults;
    }
}

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