While attempting to write out a JTextArea object to disk with DocumentListener enabled for the component cuases an exception java.io.NotSerializableException: java.io.ObjectOutputStream The more I look into this it appears the culprit
may be due to having the listeners on while trying to write out the object. With the following testcase if you comment/uncomment out
jta.getDocument().addDocumentListener(this); for
JTextArea jta = new JTextArea("This is Strange",15,50); will show what I'm talking about. Please remember that JTextArea object needs to be visible for the error
to occur. If you create a JTextArea object and enable DocumentListener for that object and then write object to disk without setting visible will always work. The root of the problems with JComponents being written to disk is with listener's being enabled for JComponents.



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Testcase JTextAreaTest.java

import java.io.*;
import javax.swing.*;
import java.awt.*;
import javax.swing.event.*;
import java.awt.event.*;

public class JTextAreaTest extends JFrame implements ActionListener, DocumentListener{

  FileOutputStream outFile;
  ObjectOutputStream freezer = null;
  JTextArea jta = new JTextArea("This is a bug",15,50);
  
  public JTextAreaTest() {
    super("JTextArea with a DocumentListener enabled bug");
    JPanel jp = new JPanel();
    
    // Comment out below line to see bug go away.
    jta.getDocument().addDocumentListener(this);

    jp.add(jta);

    JPanel buttonPanel = new JPanel();
    JButton saveMe = new JButton("Save");
    buttonPanel.add(saveMe);
    saveMe.addActionListener(this);

    //Add Components to Content Pane
    getContentPane().add(buttonPanel,BorderLayout.SOUTH);
    getContentPane().add(jp,BorderLayout.CENTER );
    
    // Add Window handler
    addWindowListener(new WindowAdapter(){
      public void windowClosing(WindowEvent event){ System.exit(0);}
    });
    pack();
    setVisible(true);
  }
  
  static public void main(String args[]) {
    new JTextAreaTest();
  }

  public void actionPerformed( ActionEvent e ) {
    System.out.println("Action Occured");
    String cmd = e.getActionCommand();
    
    if (cmd.equals("Save")) {
      try {
System.out.println("Start of writeObject call");
outFile = new FileOutputStream("tabTest");
freezer = new ObjectOutputStream(outFile);
freezer.writeObject(jta);
freezer.close();
System.out.println("Finish of writeObject call");
System.exit(0);
      }
      catch(Exception error) {
System.out.println("ERROR "+error);
System.exit(1);
      }
    }
  }
  public void insertUpdate(DocumentEvent e) {
  }
  public void removeUpdate(DocumentEvent e) {
  }
  public void changedUpdate(DocumentEvent e) {
  }
}


gary.collins@East 1999-04-16