JTree Object Serialization

Question

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.event.*;
public class FileTree1 extends JFrame
public static final ImageIcon ICON_COMPUTER = new ImageIcon("computer.gif");
public static final ImageIcon ICON_DISK = new ImageIcon("disk.gif");
public static final ImageIcon ICON_FOLDER = new ImageIcon("folder.gif");
public static final ImageIcon ICON_EXPANDEDFOLDER = new ImageIcon("expandedfolder.gif");
public String path;
JTree m_tree;
protected DefaultTreeModel m_model;
protected JTextField m_display;
public FileTree1()
//super("Directories Tree");
//setSize(400, 300);
DefaultMutableTreeNode top = new DefaultMutableTreeNode(new IconData(ICON_COMPUTER, null, "Computer"), true);
DefaultMutableTreeNode node;
File[] roots =File.listRoots();
for (int k=0; k<roots.length; k++)
node = new DefaultMutableTreeNode(new IconData(ICON_DISK,null, new FileNode(roots[k])));
top.add(node);
node.add( new DefaultMutableTreeNode(new Boolean(true)));
m_model = new DefaultTreeModel(top);
m_tree = new JTree(m_model);
m_tree.putClientProperty("JTree.lineStyle", "Angled");
TreeCellRenderer renderer = new IconCellRenderer();
m_tree.setCellRenderer(renderer);
m_tree.addTreeExpansionListener(new DirExpansionListener());
m_tree.addTreeSelectionListener(new DirSelectionListener());
m_tree.getSelectionModel().setSelectionMode(TreeSelectionModel.SINGLE_TREE_SELECTION);
m_tree.setShowsRootHandles(true);
m_tree.setEditable(false);
JScrollPane s = new JScrollPane();
s.getViewport().add(m_tree);
getContentPane().add(s, BorderLayout.CENTER);
m_display = new JTextField();
m_display.setEditable(false);
getContentPane().add(m_display, BorderLayout.NORTH);
WindowListener wndCloser = new WindowAdapter()
public void windowClosing(WindowEvent e)
System.exit(0);
addWindowListener(wndCloser);
//setVisible(true);
DefaultMutableTreeNode getTreeNode(TreePath path)
return (DefaultMutableTreeNode)(path.getLastPathComponent());
FileNode getFileNode(DefaultMutableTreeNode node)
if (node == null)
return null;
Object obj = node.getUserObject();
if (obj instanceof IconData)
obj = ((IconData)obj).getObject();
if (obj instanceof FileNode)
return (FileNode)obj;
else
return null;
// Make sure expansion is threaded and updating the tree model
// only occurs within the event dispatching thread.
class DirExpansionListener implements TreeExpansionListener
public void treeExpanded(TreeExpansionEvent event)
final DefaultMutableTreeNode node = getTreeNode(event.getPath());
final FileNode fnode = getFileNode(node);
Thread runner = new Thread()
public void run()
if (fnode != null && fnode.expand(node))
Runnable runnable = new Runnable()
public void run()
m_model.reload(node);
SwingUtilities.invokeLater(runnable);
runner.start();
public void treeCollapsed(TreeExpansionEvent event) {}
class DirSelectionListener implements TreeSelectionListener
public void valueChanged(TreeSelectionEvent event)
DefaultMutableTreeNode node = getTreeNode(event.getPath());
FileNode fnode = getFileNode(node);
if (fnode != null)
m_display.setText(fnode.getFile().getAbsolutePath());
path=fnode.getFile().getAbsolutePath();
System.out.println(path);
else
m_display.setText("");
/*public static void main(String argv[])
try
UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
catch (Exception evt)
new FileTree1();
class IconCellRenderer extends JLabel implements TreeCellRenderer
protected Color m_textSelectionColor;
protected Color m_textNonSelectionColor;
protected Color m_bkSelectionColor;
protected Color m_bkNonSelectionColor;
protected Color m_borderSelectionColor;
protected boolean m_selected;
public IconCellRenderer()
super();
m_textSelectionColor = UIManager.getColor("Tree.selectionForeground");
m_textNonSelectionColor = UIManager.getColor("Tree.textForeground");
m_bkSelectionColor = UIManager.getColor("Tree.selectionBackground");
m_bkNonSelectionColor = UIManager.getColor("Tree.textBackground");
m_borderSelectionColor = UIManager.getColor("Tree.selectionBorderColor");
setOpaque(false);
public Component getTreeCellRendererComponent(JTree tree,Object value, boolean sel, boolean expanded, boolean leaf,int row, boolean hasFocus)
DefaultMutableTreeNode node =(DefaultMutableTreeNode)value;
Object obj = node.getUserObject();
setText(obj.toString());
if (obj instanceof Boolean)
setText("Retrieving data...");
if (obj instanceof IconData)
IconData idata = (IconData)obj;
if (expanded)
setIcon(idata.getExpandedIcon());
else
setIcon(idata.getIcon());
else
setIcon(null);
setFont(tree.getFont());
setForeground(sel ? m_textSelectionColor : m_textNonSelectionColor);
setBackground(sel ? m_bkSelectionColor : m_bkNonSelectionColor);
m_selected = sel;
return this;
public void paintComponent(Graphics g)
Color bColor = getBackground();
Icon icon = getIcon();
g.setColor(bColor);
int offset = 0;
if(icon != null && getText() != null)
offset = (icon.getIconWidth() + getIconTextGap());
g.fillRect(offset, 0, getWidth() - 1 - offset,
getHeight() - 1);
if (m_selected)
g.setColor(m_borderSelectionColor);
g.drawRect(offset, 0, getWidth()-1-offset, getHeight()-1);
super.paintComponent(g);
class IconData
protected Icon m_icon;
protected Icon m_expandedIcon;
protected Object m_data;
public IconData(Icon icon, Object data)
m_icon = icon;
m_expandedIcon = null;
m_data = data;
public IconData(Icon icon, Icon expandedIcon, Object data)
m_icon = icon;
m_expandedIcon = expandedIcon;
m_data = data;
public Icon getIcon()
return m_icon;
public Icon getExpandedIcon()
return m_expandedIcon!=null ? m_expandedIcon : m_icon;
public Object getObject()
return m_data;
public String toString()
return m_data.toString();
class FileNode
protected File m_file;
public FileNode(File file)
m_file = file;
public File getFile()
return m_file;
public String toString()
return m_file.getName().length() > 0 ? m_file.getName() : m_file.getPath();
public boolean expand(DefaultMutableTreeNode parent)
DefaultMutableTreeNode flag = (DefaultMutableTreeNode)parent.getFirstChild();
if (flag==null) // No flag
return false;
Object obj = flag.getUserObject();
if (!(obj instanceof Boolean))
return false; // Already expanded
parent.removeAllChildren(); // Remove Flag
File[] files =listFiles();
if (files == null)
return true;
Vector v = new Vector();
for (int k=0; k<files.length; k++)
//System.out.println(files[k].getName());
File f = files[k];
//if (!(f.isDirectory()))
//continue;
FileNode newNode = new FileNode(f);
//System.out.println(newNode);
boolean isAdded = false;
for (int i=0; i<v.size(); i++)
FileNode nd = (FileNode)v.elementAt(i);
if (newNode.compareTo(nd) < 0)
v.insertElementAt(newNode, i);
isAdded = true;
break;
if (!isAdded)
v.addElement(newNode);
for (int i=0; i<v.size(); i++)
FileNode nd = (FileNode)v.elementAt(i);
IconData idata = new IconData(FileTree1.ICON_FOLDER,FileTree1.ICON_EXPANDEDFOLDER, nd);
DefaultMutableTreeNode node = new DefaultMutableTreeNode(idata);
parent.add(node);
if (nd.hasSubDirs())
node.add(new DefaultMutableTreeNode(new Boolean(false) ));
return true;
public boolean hasSubDirs()
File[] files = listFiles();
if (files == null)
return false;
for (int k=0; k<files.length; k++)
//if (files[k].isDirectory())
return true;
return false;
public int compareTo(FileNode toCompare)
return m_file.getName().compareToIgnoreCase(toCompare.m_file.getName() );
protected File[] listFiles()
//if (m_file.isDirectory())
//return m_file.listFiles();
try
return m_file.listFiles();
catch (Exception ex)
JOptionPane.showMessageDialog(null,"Error reading directory "+m_file.getAbsolutePath(),"Warning", JOptionPane.WARNING_MESSAGE);
return null;

Answer 1

The code which shown above is a JTree that shows complete file system.
Please tell me how to persist the JTree Object using XMLEncoder and
XMLDecoder for the above code.