How to create Java bean component
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Font;
import java.awt.Graphics;
import java.beans.PropertyChangeListener;
import java.beans.PropertyVetoException;
import java.beans.VetoableChangeListener;
import java.beans.VetoableChangeSupport;
import java.io.Externalizable;
import java.io.IOException;
import java.io.ObjectInput;
import java.io.ObjectOutput;
import javax.swing.JComponent;
import javax.swing.JFrame;
import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;
import javax.swing.event.EventListenerList;
import javax.swing.event.SwingPropertyChangeSupport;
public class BakedBean extends JComponent implements Externalizable {
// Property names
public static final String BEAN_VALUE = "Value";
public static final String BEAN_COLOR = "Color";
// Properties
private Font beanFont; // simple
private Dimension beanDimension; // simple
private int beanValue; // bound
private Color beanColor; // constrained
private String text; // change
// Manages all PropertyChangeListeners
protected SwingPropertyChangeSupport propertySupporter = new SwingPropertyChangeSupport(
this);
// Manages all VetoableChangeListeners
protected VetoableChangeSupport vetoableChangeSupport = new VetoableChangeSupport(this);
protected transient ChangeEvent changeEvent = null;
protected EventListenerList listenerList = new EventListenerList();
public BakedBean() {
beanFont = new Font("SanSerif", Font.BOLD | Font.ITALIC, 12);
beanDimension = new Dimension(150, 100);
beanValue = 0;
beanColor = Color.black;
text = "BakedBean #";
}
public void paintComponent(Graphics g) {
super.paintComponent(g);
g.setColor(beanColor);
g.setFont(beanFont);
g.drawString(text + beanValue, 30, 30);
}
public void setBeanFont(Font font) {
beanFont = font;
}
public Font getBeanFont() {
return beanFont;
}
public void setBeanValue(int newValue) {
int oldValue = beanValue;
beanValue = newValue;
// Notify all PropertyChangeListeners
propertySupporter.firePropertyChange(BEAN_VALUE, new Integer(oldValue),
new Integer(newValue));
}
public int getBeanValue() {
return beanValue;
}
public void setBeanColor(Color newColor) throws PropertyVetoException {
Color oldColor = beanColor;
vetoableChangeSupport.fireVetoableChange(BEAN_COLOR, oldColor, newColor);
beanColor = newColor;
propertySupporter.firePropertyChange(BEAN_COLOR, oldColor, newColor);
}
public Color getBeanColor() {
return beanColor;
}
public void setBeanString(String newString) {
text = newString;
// Notify all ChangeListeners
fireStateChanged();
}
public String getBeanString() {
return text;
}
public void setPreferredSize(Dimension dim) {
beanDimension = dim;
}
public Dimension getPreferredSize() {
return beanDimension;
}
public void setMinimumSize(Dimension dim) {
beanDimension = dim;
}
public Dimension getMinimumSize() {
return beanDimension;
}
public void addPropertyChangeListener(PropertyChangeListener l) {
propertySupporter.addPropertyChangeListener(l);
}
public void removePropertyChangeListener(PropertyChangeListener l) {
propertySupporter.removePropertyChangeListener(l);
}
public void addVetoableChangeListener(VetoableChangeListener l) {
vetoableChangeSupport.addVetoableChangeListener(l);
}
public void removeVetoableChangeListener(VetoableChangeListener l) {
vetoableChangeSupport.removeVetoableChangeListener(l);
}
// Remember that EventListenerList is an array of
// key/value pairs.
// key = XXListener class reference
// value = XXListener instance
public void addChangeListener(ChangeListener l) {
listenerList.add(ChangeListener.class, l);
}
public void removeChangeListener(ChangeListener l) {
listenerList.remove(ChangeListener.class, l);
}
// EventListenerList dispatching code.
protected void fireStateChanged() {
Object[] listeners = listenerList.getListenerList();
// Process the listeners last to first, notifying
// those that are interested in this event
for (int i = listeners.length - 2; i >= 0; i -= 2) {
if (listeners[i] == ChangeListener.class) {
if (changeEvent == null)
changeEvent = new ChangeEvent(this);
((ChangeListener) listeners[i + 1]).stateChanged(changeEvent);
}
}
}
public void writeExternal(ObjectOutput out) throws IOException {
out.writeObject(beanFont);
out.writeObject(beanDimension);
out.writeInt(beanValue);
out.writeObject(beanColor);
out.writeObject(text);
}
public void readExternal(ObjectInput in) throws IOException,
ClassNotFoundException {
setBeanFont((Font) in.readObject());
setPreferredSize((Dimension) in.readObject());
// Use preferred size for minimum size..
setMinimumSize(getPreferredSize());
setBeanValue(in.readInt());
try {
setBeanColor((Color) in.readObject());
} catch (PropertyVetoException pve) {
System.out.println("Color change vetoed..");
}
setBeanString((String) in.readObject());
}
public static void main(String[] args) {
JFrame frame = new JFrame("BakedBean");
frame.getContentPane().add(new BakedBean());
frame.setVisible(true);
frame.pack();
}
}
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