"Java Alley" by Bruce Eckel Web Techniques, September 1997 Web Techniques grants permission to use these listings for private or commercial use provided that credit to Web Techniques and the author is maintained within the comments of the source. For questions, contact [email protected]. LISTING ONE //: Frog.java // A trivial Java bean import java.awt.*; import java.awt.event.*; class Spots {} public class Frog { private int jumps; private Color color; private Spots spots; private boolean jmpr; public int getJumps() { return jumps; } public void setJumps(int newJumps) { jumps = newJumps; } public Color getColor() { return color; } public void setColor(Color newColor) { color = newColor; } public Spots getSpots() { return spots; } public void setSpots(Spots newSpots) { spots = newSpots; } public boolean isJumper() { return jmpr; } public void setJumper(boolean j) { jmpr = j; } public void addActionListener( ActionListener l) { //... } public void removeActionListener( ActionListener l) { // ... } public void addKeyListener(KeyListener l) { // ... } public void removeKeyListener(KeyListener l) { // ... } // An "ordinary" public method: public void croak() { System.out.println("Ribbet!"); } LISTING TWO //: BeanDumper.java // A method to introspect a bean import java.beans.*; import java.lang.reflect.*; public class BeanDumper { public static void dump(Class bean){ BeanInfo bi = null; try { bi = Introspector.getBeanInfo( bean, java.lang.Object.class); } catch(IntrospectionException ex) { System.out.println("Couldn't introspect " + bean.getName()); System.exit(1); } PropertyDescriptor properties[] = bi.getPropertyDescriptors(); for(int i = 0; i < properties.length; i++) { Class p = properties[i].getPropertyType(); System.out.println( "Property type:\n " + p.getName()); System.out.println( "Property name:\n " + properties[i].getName()); Method readMethod = properties[i].getReadMethod(); if(readMethod != null) System.out.println( "Read method:\n " + readMethod.toString()); Method writeMethod = properties[i].getWriteMethod(); if(writeMethod != null) System.out.println( "Write method:\n " + writeMethod.toString()); System.out.println("===================="); } System.out.println("Public methods:"); MethodDescriptor methods[] = bi.getMethodDescriptors(); for(int i = 0; i < methods.length; i++) System.out.println( methods[i].getMethod().toString()); System.out.println("======================"); System.out.println("Event support:"); EventSetDescriptor events[] = bi.getEventSetDescriptors(); for(int i = 0; i < events.length; i++) { System.out.println("Listener type:\n " + events[i].getListenerType().getName()); Method lm[] = events[i].getListenerMethods(); for(int j = 0; j < lm.length; j++) System.out.println( "Listener method:\n " + lm[j].getName()); MethodDescriptor lmd[] = events[i].getListenerMethodDescriptors(); for(int j = 0; j < lmd.length; j++) System.out.println( "Method descriptor:\n " + lmd[j].getMethod().toString()); Method addListener = events[i].getAddListenerMethod(); System.out.println( "Add Listener Method:\n " + addListener.toString()); Method removeListener = events[i].getRemoveListenerMethod(); System.out.println( "Remove Listener Method:\n " + removeListener.toString()); System.out.println("===================="); } } // Dump the class of your choice: public static void main(String args[]) { if(args.length < 1) { System.err.println("usage: \n" + "BeanDumper fully.qualified.class"); System.exit(0); } Class c = null; try { c = Class.forName(args[0]); } catch(ClassNotFoundException ex) \{ System.err.println( "Couldn't find " + args[0]); System.exit(0); } dump(c); } LISTING THREE class name: Frog Property type: Color Property name: color Read method: public Color getColor() Write method: public void setColor(Color) ==================== Property type: Spots Property name: spots Read method: public Spots getSpots() Write method: public void setSpots(Spots) ==================== Property type: boolean Property name: jumper Read method: public boolean isJumper() Write method: public void setJumper(boolean) ==================== Property type: int Property name: jumps Read method: public int getJumps() Write method: public void setJumps(int) ==================== Public methods: public void setJumps(int) public void croak() public void removeActionListener(ActionListener) public void addActionListener(ActionListener) public int getJumps() public void setColor(Color) public void setSpots(Spots) public void setJumper(boolean) public boolean isJumper() public void addKeyListener(KeyListener) public Color getColor() public void removeKeyListener(KeyListener) public Spots getSpots() ====================== Event support: Listener type: KeyListener Listener method: keyTyped Listener method: keyPressed Listener method: keyReleased Method descriptor: public void keyTyped(KeyEvent) Method descriptor: public void keyPressed(KeyEvent) Method descriptor: public void keyReleased(KeyEvent) Add Listener Method: public void addKeyListener(KeyListener) Remove Listener Method: public void removeKeyListener(KeyListener) ==================== Listener type: ActionListener Listener method: actionPerformed Method descriptor: public void actionPerformed(ActionEvent) Add Listener Method: public void addActionListener(ActionListener) Remove Listener Method: public void removeActionListener(ActionListener) LISTING FOUR //: TestBangBean.java // A graphical Bean import java.awt.*; import java.awt.event.*; import java.util.*; import java.io.*; class BangBean extends Canvas implements Serializable { private int xm, ym; private int cSize = 20; // Circle size private String text = "Bang!"; private int fontSize = 48; private Color tColor = Color.red; private ActionListener actionListener; public BangBean() { addMouseListener(new ML()); addMouseMotionListener(new MM()); } public int getCircleSize() { return cSize; } public void setCircleSize(int newSize) { cSize = newSize; } public String getBangText() { return text; } public void setBangText(String newText) { text = newText; } public int getFontSize() { return fontSize; } public void setFontSize(int newSize) { fontSize = newSize; } public Color getTextColor() { return tColor; } public void setTextColor(Color newColor) { tColor = newColor; } public void paint(Graphics g) { g.setColor(Color.black); g.drawOval(xm - cSize/2, ym - cSize/2, cSize, cSize); } // This is a unicast listener, which is // the simplest form of listener management: public void addActionListener ( ActionListener l) throws TooManyListenersException { if(actionListener != null) throw new TooManyListenersException(); actionListener = l; } public void removeActionListener( ActionListener l) { actionListener = null; } class ML extends MouseAdapter { public void mousePressed(MouseEvent e) { Graphics g = getGraphics(); g.setColor(tColor); g.setFont( new Font( "TimesRoman", Font.BOLD, fontSize)); int width = g.getFontMetrics().stringWidth(text); g.drawString(text, (getSize().width - width) /2, getSize().height/2); g.dispose(); // Call the listener's method: if(actionListener != null) actionListener.actionPerformed( new ActionEvent(BangBean.this, ActionEvent.ACTION_PERFORMED, null)); } } class MM extends MouseMotionAdapter { public void mouseMoved(MouseEvent e) { xm = e.getX(); ym = e.getY(); repaint(); } } } public class TestBangBean extends Frame { BangBean bb = new BangBean(); public TestBangBean() \{ setTitle("BangBean Test"); addWindowListener(new WL()); setSize(300,300); add(bb, BorderLayout.CENTER); try { bb.addActionListener(new BBL()); } catch(TooManyListenersException e) {} } class WL extends WindowAdapter { public void windowClosing(WindowEvent e) { System.exit(0); } } class BBL implements ActionListener { public void actionPerformed(ActionEvent e) { System.out.println("BangBean action"); } } public static void main(String args[]) { Frame f = new TestBangBean(); f.setVisible(true); } }
Java Alley | JavaBeans from Square One (Web Techniques, Sep 1997)
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