PropertyTable : Java Beans « Development Class « Java


 * Copyright (c) 2000 David Flanagan.  All rights reserved.
 * This code is from the book Java Examples in a Nutshell, 2nd Edition.
 * It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
 * You may study, use, and modify it for any non-commercial purpose.
 * You may distribute it non-commercially as long as you retain this notice.
 * For a commercial use license, or to purchase the book (recommended),
 * visit

import java.beans.BeanInfo;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.util.Arrays;
import java.util.Comparator;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingConstants;
import javax.swing.table.AbstractTableModel;
import javax.swing.table.DefaultTableCellRenderer;
import javax.swing.table.TableColumn;
import javax.swing.table.TableColumnModel;

 * This class is a JTable subclass that displays a table of the JavaBeans
 * properties of any specified class.
public class PropertyTable extends JTable {
  /** This main method allows the class to be demonstrated standalone */
  public static void main(String[] args) {
    // Specify the name of the class as a command-line argument
    Class beanClass = null;
    try {
      // Use reflection to get the Class from the classname
      beanClass = Class.forName("javax.swing.JLabel");
    } catch (Exception e) { // Report errors
      System.out.println("Can't find specified class: " + e.getMessage());
      System.out.println("Usage: java TableDemo <JavaBean class name>");

    // Create a table to display the properties of the specified class
    JTable table = new PropertyTable(beanClass);

    // Then put the table in a scrolling window, put the scrolling
    // window into a frame, and pop it all up on to the screen
    JScrollPane scrollpane = new JScrollPane(table);
    JFrame frame = new JFrame("Properties of JavaBean: ");
    frame.setSize(500, 400);

   * This constructor method specifies what data the table will display (the
   * table model) and uses the TableColumnModel to customize the way that the
   * table displays it. The hard work is done by the TableModel implementation
   * below.
  public PropertyTable(Class beanClass) {
    // Set the data model for this table
    try {
      setModel(new JavaBeanPropertyTableModel(beanClass));
    } catch (IntrospectionException e) {
      System.err.println("WARNING: can't introspect: " + beanClass);

    // Tweak the appearance of the table by manipulating its column model
    TableColumnModel colmodel = getColumnModel();

    // Set column widths

    // Right justify the text in the first column
    TableColumn namecol = colmodel.getColumn(0);
    DefaultTableCellRenderer renderer = new DefaultTableCellRenderer();

   * This class implements TableModel and represents JavaBeans property data
   * in a way that the JTable component can display. If you've got some type
   * of tabular data to display, implement a TableModel class to describe that
   * data, and the JTable component will be able to display it.
  static class JavaBeanPropertyTableModel extends AbstractTableModel {
    PropertyDescriptor[] properties; // The properties to display

     * The constructor: use the JavaBeans introspector mechanism to get
     * information about all the properties of a bean. Once we've got this
     * information, the other methods will interpret it for JTable.
    public JavaBeanPropertyTableModel(Class beanClass)
        throws java.beans.IntrospectionException {
      // Use the introspector class to get "bean info" about the class.
      BeanInfo beaninfo = Introspector.getBeanInfo(beanClass);
      // Get the property descriptors from that BeanInfo class
      properties = beaninfo.getPropertyDescriptors();
      // Now do a case-insensitive sort by property name
      // The anonymous Comparator implementation specifies how to
      // sort PropertyDescriptor objects by name
      Arrays.sort(properties, new Comparator() {
        public int compare(Object p, Object q) {
          PropertyDescriptor a = (PropertyDescriptor) p;
          PropertyDescriptor b = (PropertyDescriptor) q;
          return a.getName().compareToIgnoreCase(b.getName());

        public boolean equals(Object o) {
          return o == this;

    // These are the names of the columns represented by this TableModel
    static final String[] columnNames = new String[] { "Name", "Type",
        "Access", "Bound" };

    // These are the types of the columns represented by this TableModel
    static final Class[] columnTypes = new Class[] { String.class,
        Class.class, String.class, Boolean.class };

    // These simple methods return basic information about the table
    public int getColumnCount() {
      return columnNames.length;

    public int getRowCount() {
      return properties.length;

    public String getColumnName(int column) {
      return columnNames[column];

    public Class getColumnClass(int column) {
      return columnTypes[column];

     * This method returns the value that appears at the specified row and
     * column of the table
    public Object getValueAt(int row, int column) {
      PropertyDescriptor prop = properties[row];
      switch (column) {
      case 0:
        return prop.getName();
      case 1:
        return prop.getPropertyType();
      case 2:
        return getAccessType(prop);
      case 3:
        return new Boolean(prop.isBound());
        return null;

    // A helper method called from getValueAt() above
    String getAccessType(PropertyDescriptor prop) {
      java.lang.reflect.Method reader = prop.getReadMethod();
      java.lang.reflect.Method writer = prop.getWriteMethod();
      if ((reader != null) && (writer != null))
        return "Read/Write";
      else if (reader != null)
        return "Read-Only";
      else if (writer != null)
        return "Write-Only";
        return "No Access"; // should never happen


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