JDBC virgin needs help.

Question

Hi, I am a 2nd year university student doing JDBC for the first time.
I think my problem lies in the ODBC data sources rather than the code since the code works on the machine in university (NT) but not on my home PC (XP). When I run the code I get no errors but nothing happens in terms of interrogating or writing to the database (Access).
I have tried a crude debug by performing a System.out.print at various stages and the result is that the message will display before I implement executeUpdate but not after. Any wise tips on how to ensure that my database is set up and working properly in XP? (I am sure this is the root of the problem rather than the code <supplied here anyway>)
import java.sql.*;
import java.io.DataInputStream;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;
public class JDBCFrame extends JFrame implements ActionListener{
     JButton insert,extract,edit,delete;
     JTextField textid,textname;
     JTextArea output;
     JScrollPane scroll;
     Connection db_connection;
     Statement db_statement;
     public JDBCFrame(){
          // set up GUI
          Container content = this.getContentPane();
          content.setLayout(new GridLayout(5,1));
          textid=new JTextField("ID goes here");
          textname = new JTextField("Name goes here");
          content.add(textid);
          content.add(textname);
          insert = new JButton("Insert");
          insert.addActionListener(this);
          extract = new JButton("Extract");
          extract.addActionListener(this);
          edit = new JButton("Edit");
          edit.addActionListener(this);
          delete = new JButton("Delete");
          delete.addActionListener(this);
          content.add(insert);
          content.add(extract);
          content.add(edit);
          content.add(delete);
          output = new JTextArea();
          scroll = new JScrollPane(output);
          content.add(scroll);
          try{
               Class.forName("sun.jdbc.odbc.JdbcOdbcDriver").newInstance();
               //String url = "jdbc:odbc:"+"demo";
               String url = "jdbc:odbc:demo";
               //String url = "jdbc:odbc:;Driver={Microsoft Access Driver (*.mdb)};DBQ=demo.mdb";
               db_connection = DriverManager.getConnection(url,"","");
          catch(Exception ce){}
     public void actionPerformed(ActionEvent ev){
          if(ev.getSource()==extract){
               try{
                    extract();
               catch(Exception e){}
          if(ev.getSource()==edit){
               try{
                    edit();
               catch(Exception e){}
          if(ev.getSource()==insert){
               try{
                    insert();
               catch(Exception e){}
          if(ev.getSource()==delete){
               try{
                    delete();
               catch(Exception e){}
     public void edit() throws Exception{
          String names = textname.getText();
          String id = textid.getText();
          System.out.print("*** Connecting ***");
          db_statement.executeUpdate("UPDATE employee SET name="+names+"WHERE ID="+id);
          db_connection.commit();
     public void insert() throws Exception{
          String names = textname.getText();
          String id = textid.getText();
          db_statement.executeUpdate("INSERT INTO employee VALUES("+id+","+names+")");
          db_connection.commit();
     public void delete() throws Exception{
          String id = textid.getText();
          db_statement.executeUpdate("DELETE FROM employee WHERE ID= "+textid.getText());
     public void extract() throws Exception{
          output.setText("");
          if(textname.getText().equals("")){
               ResultSet result2 = db_statement.executeQuery("SELECT * FROM employee WHERE ID="+textid.getText());
               while(result2.next()){
                    output.setText(output.getText()+"ID:"+result2.getInt("ID")+"t"+result2.getString("Name")+"\n");
          ResultSet result=db_statement.executeQuery("SELECT * FROM employee WHERE name="+textname.getText()+"");
          while(result.next()){
               output.setText(output.getText()+"ID:"+result.getInt("ID")+"\t"+result.getString("Name")+"\n");
     public static void main(String args[]){
          JDBCFrame win=new JDBCFrame();
          win.setSize(100,200);
          win.setVisible(true);
          win.addWindowListener(new WindowAdapter(){
               public void windowClosing(WindowEvent e){
                    System.exit(0);
          

Answer 1

Obviously "NullPointerException", because "db_statement" IS NEVER ASSIGNED A VALUE! [D'OH]
Aren't you missing some code, like:
db_statement = db_connection.createStatement();(for example)?
Hope this helps.
Good Luck,
Avi.