Real Model View Controller with JTextField

Question

Hi!
I am new to Java (so please bear with me). I am building a swing application. I already have added a JTable with a corresponding table model that extends AbstractTableModel. Rather than store the data in the table model, I have modified setValueAt and getValueAt to write and read cell data to another location. So far, everything is fine. When doing setValueAt, I have a fireTableCellUpdated statement that I use to update the edited cell. So far, things are all still fine.
I would like to do the same thing with a JTextField. I found an example in Core Java Volume 1 for create a class that extends PlainDocument. It uses insertString to update the document in a way that ensures that only numbers are entered. I implemented this. Everything is still fine. I changed insertString to update my remote repository (a field in another class). Everything is still fine. Next, I tried to change (override) both getText methods to read from the repository. This works, but is not reflected on the screen.
I realize that I need the equivalent of a fireTableCellUpdated statement for the class that extends PlainDocument, but do not know how to do this.
I have looked a lot over the internet for the model view controller implementation. I know that it can be done using event and event listeners, but this seems to defeat the purpose of the model view controller - it seems like you ought to be able to directly modify the model object to access external data.
My code is below.
Thanks/Phil Troy
* PlainDocument class to make it possible to:
* - Make sure input in unsigned integer
* - Automatically save data to appropriate locate
* This will hopefully eventually work by overriding the insertString and getText methods
* and creating methods that can be overridden to get and save the numerical value
class UnsignedIntegerDocument extends PlainDocument
     TutorSchedulerPlusSettings settings;
     JTextField textField;
     public UnsignedIntegerDocument(TutorSchedulerPlusSettings settings)
     {     super();
          this.settings = settings;
     public void setTextField(JTextField textField)
     {     this.textField = textField;
     // Overridden method
     public void insertString(int offs, String str, AttributeSet a) throws BadLocationException
     {     if (str == null) return;
          String oldString = getText(0, getLength());
          String newString = oldString.substring(0, offs) + str +oldString.substring(offs);
          try
          {     setValue(Integer.parseInt(newString));
               super.insertString(offs, str, a);
               fireInsertUpdate(new DefaultDocumentEvent(offs, 10, DocumentEvent.EventType.INSERT));
          catch(NumberFormatException e)
     public String getText()
     {     return String.valueOf(getValue());
     public String getText(int offset, int length) throws BadLocationException
     {     String s = String.valueOf(getValue());
          if (length > 0)
               s = s.substring(offset, length);
          return s;
     public void getText(int offset, int length, Segment txt) throws BadLocationException
     {     //super.getText(offset, length, txt);
          char[] c = new char[10];
          String s = String.valueOf(getValue());
          s.getChars(offset, length, c, 0);
          txt = new Segment(c, 0, length);
     public String getValue()
     {     int i = settings.maxStudents;
          String s = String.valueOf(i);
          return s;          
     void setValue(int i)
     {     settings.maxStudents = i;
}

Answer 1

Hi!
Thanks for your response. Unfortunately, based on your response, I guess that I must not have clearly communicated what I am trying to do.
I am using both JTables and JTextFields, and would like to use them both in the same way.
When using JTable, I extend an AbstractTableModel so that it refers to another data source (in a separate class), rather than one inside of the AbstractTableModel. Thus the getValueAt method, getColumnCount method, setValueAt method, . .. all call methods in another class. The details of that other class are irrelevant, but they could be accessing data from a database (via JDBC) or from other machines via some other communication mechanism.
I would like to do exactly the same thing with a JTextField. I wish for the data to come from a class other than an object of type PlainDocument, or of any class that implements the Document interface. Instead, I would like to use a class that implements the Document interface to call my external class using methods similar to those found in AbstractTableModel.
You may ask why I would like to to this. I have specific reasons here, but more generally this would be helpful when saving or retrieving parameters set and displayed in a JTextField to a database, or when sharing JTextField to multiple users located on different machines.
As to whether this is real MVC or not, I think it is but it really doesn't matter.
I know that I can accomplish what I want for the JTextField using listeners. However, I would like my code for the JTables to be similarly structured to that of the JTextField.
Thanks/Phil Troy