Introspecting a Bean
// : c14:BeanDumper.java
// Introspecting a Bean.
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.beans.BeanInfo;
import java.beans.EventSetDescriptor;
import java.beans.IntrospectionException;
import java.beans.Introspector;
import java.beans.MethodDescriptor;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Method;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
public class BeanDumper extends JFrame {
private JTextField query = new JTextField(20);
private JTextArea results = new JTextArea();
public void print(String s) {
results.append(s + "\n");
}
public void dump(Class bean) {
results.setText("");
BeanInfo bi = null;
try {
bi = Introspector.getBeanInfo(bean, Object.class);
} catch (IntrospectionException e) {
print("Couldn't introspect " + bean.getName());
return;
}
PropertyDescriptor[] properties = bi.getPropertyDescriptors();
for (int i = 0; i < properties.length; i++) {
Class p = properties[i].getPropertyType();
if (p == null)
continue;
print("Property type:\n " + p.getName() + "Property name:\n "
+ properties[i].getName());
Method readMethod = properties[i].getReadMethod();
if (readMethod != null)
print("Read method:\n " + readMethod);
Method writeMethod = properties[i].getWriteMethod();
if (writeMethod != null)
print("Write method:\n " + writeMethod);
print("====================");
}
print("Public methods:");
MethodDescriptor[] methods = bi.getMethodDescriptors();
for (int i = 0; i < methods.length; i++)
print(methods[i].getMethod().toString());
print("======================");
print("Event support:");
EventSetDescriptor[] events = bi.getEventSetDescriptors();
for (int i = 0; i < events.length; i++) {
print("Listener type:\n " + events[i].getListenerType().getName());
Method[] lm = events[i].getListenerMethods();
for (int j = 0; j < lm.length; j++)
print("Listener method:\n " + lm[j].getName());
MethodDescriptor[] lmd = events[i].getListenerMethodDescriptors();
for (int j = 0; j < lmd.length; j++)
print("Method descriptor:\n " + lmd[j].getMethod());
Method addListener = events[i].getAddListenerMethod();
print("Add Listener Method:\n " + addListener);
Method removeListener = events[i].getRemoveListenerMethod();
print("Remove Listener Method:\n " + removeListener);
print("====================");
}
}
class Dumper implements ActionListener {
public void actionPerformed(ActionEvent e) {
String name = query.getText();
Class c = null;
try {
c = Class.forName(name);
} catch (ClassNotFoundException ex) {
results.setText("Couldn't find " + name);
return;
}
dump(c);
}
}
public BeanDumper() {
Container cp = getContentPane();
JPanel p = new JPanel();
p.setLayout(new FlowLayout());
p.add(new JLabel("Qualified bean name:"));
p.add(query);
cp.add(BorderLayout.NORTH, p);
cp.add(new JScrollPane(results));
Dumper dmpr = new Dumper();
query.addActionListener(dmpr);
query.setText("frogbean.Frog");
// Force evaluation
dmpr.actionPerformed(new ActionEvent(dmpr, 0, ""));
}
public static void main(String[] args) {
run(new BeanDumper(), 600, 500);
}
public static void run(JFrame frame, int width, int height) {
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setSize(width, height);
frame.setVisible(true);
}
} ///:~
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