Question: after I define a kind of file format, it is dificult for hosting providers to
register it for my site? i can ask that after i paid the service? it must be a mime type properly register at ietf.

thanks in advance

Answer: 
Try adding a [KeyListener](http://java.sun.com/javase/6/docs/api/java/awt/Component.html#addKeyListener%28java.awt.event.KeyListener%29) on the JTextField
Is the user allow to paste text? (Can they right click and select paste?)

If so, KeyListeners won't work and you'll need DocumentListeners.