Using a Document Listener to update a text field

Question

Hi,
Background:
I need to retrieve a number from a card using a hand scanner. I'm currently using a jTextField1 in Netbeans to do this. When the number is input (the format is 6 digits, i.e. 123456) the rest of the form fields are filled in and updated automatically from an oracle database as it should. I have the database being checked as soon as the field reaches 6 characters (doc.getLength() == 6), It all works great.
Problem:
The problem comes in when I need to input a card that has a newer, different format of numbers and characters, i.e. **001234567**, it's more than 6 characters. I need only the 123456 substring to update the form, and the 7 substring to input later.
What I tried:
I'm using the combination of pattern matching and substring to get the 1234567 part only. I thought of using a hidden field on the form to input the numbers to and then set the text of jTextField1. I'm not sure this would work and seems like a hack anyways.
Code:
        public void updateLog(DocumentEvent e, String action) {
        Document doc = (Document) e.getDocument();
        Integer docLength = doc.getLength();
        String isCardLegal = jTextField1.getText(); // getting card from textbox
        returnString Del = new returnString();
        String str = Del.getNewNumberFromCard(isCardLegal);
        System.out.println("str: "  +str);
        if (docLength == 6) {
          // see if number exists in database here
public class returnString {
    public String getNewNumberFromCard(String oldString) {
        Pattern p = Pattern.compile("\\*");
        Matcher m = p.matcher(oldString);
        String newString = m.replaceAll("");
        // takes off leading zeros when using a new card
        // otherwise just returns the string as-is
        if (newString.length() == 9) {
            newString = newString.substring(2);
            return newString;
        } else {
            return newString;
}Does anyone have a better way to do this? I hope I was clear in my explanation.
Thank You for your help,
Alan
Edited by: shadow_coder on Oct 8, 2009 12:01 PM

Answer 1

I really thank you for your help, I realize I wasn't clear because I wasn't sure about too many different things. I'll try it again:
I need to use a hand scanner to input id cards having 2 different character sets. I now realize I can have the scanner insert a carriage return at the end of the scan, so I need to be able to detect this carriage return. I'm using a documentlistener to look at each character in the textfield. The character sets I need to use are 6 characters long, and an 11 character long set (including asterisks).
Here is my SSCCE:
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.event.DocumentEvent;
import javax.swing.event.DocumentListener;
import javax.swing.text.BadLocationException;
import javax.swing.text.Document;
public class exampleCase extends JFrame implements ActionListener {
    JTextField textField1;
    public exampleCase() {
        getContentPane().setLayout(new FlowLayout());
        textField1 = new JTextField(15);
        textField1.getDocument().addDocumentListener(new MyDocumentListener());
        textField1.getDocument().putProperty("name", "TextField");
        getContentPane().add(textField1);
        setSize(300, 170);
        setVisible(true);
    public static void main(String argv[]) {
        new exampleCase();
    public void actionPerformed(ActionEvent e) {
        throw new UnsupportedOperationException("Not supported yet.");
    class MyDocumentListener implements DocumentListener {
        public void insertUpdate(DocumentEvent e) {
            updateLog(e, "inserted into ");
        public void removeUpdate(DocumentEvent e) {
            updateLog(e, "removed from ");
        public void changedUpdate(DocumentEvent e) {
            throw new UnsupportedOperationException("Not supported yet.");
        public void updateLog(DocumentEvent e, String action) {
            String newline = "\n";
            Document doc = (Document) e.getDocument();
            int changeLength = e.getLength();
            System.out.println(
                    changeLength  +" character"+
                    ((changeLength == 1) ? " " : "s ")
                    action+  doc.getProperty("name")  +"."+  newline
                    "  Text length = "+  doc.getLength()  +newline);
           try {
                String docCharacters = doc.getText(0, 2); // Exception when increased
                System.out.println("Characters are: "+  docCharacters);
                if (docCharacters.equals("\\r")) { // How to check for carriage return?
                    System.out.println("I'm Here, Yeeaaah!!");
            } catch (BadLocationException ex) {
               System.out.println("Error Here, bad location" + ex);
}When I increase the '2' to be able to handle the characters, I get javax.swing.text.BadLocationException: Invalid location can anyone tell me why? I'm not sure why it works when the number is at 2 but not others!
The other issue is, what is the correct way to detect a carriage return? I was able to test this when the number above was at 2. This doesn't work.