How do I list property names of a Bean?

package org.kodejava.example.bean;

import java.io.Serializable;
import java.beans.BeanInfo;
import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.beans.IntrospectionException;

public class Fruit implements Serializable {
    private Long id;
    private String name;
    private String latinName;
    private double price;

    public Fruit() {
    }

    public static void main(String[] args) {
        try {
            BeanInfo bi = Introspector.getBeanInfo(Fruit.class);
            PropertyDescriptor[] pds = bi.getPropertyDescriptors();

            for (PropertyDescriptor pd : pds) {
                String propertyName = pd.getName();

                System.out.println("propertyName = " + propertyName);
            }
        } catch (IntrospectionException e) {
            e.printStackTrace();
        }
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getLatinName() {
        return latinName;
    }

    public void setLatinName(String latinName) {
        this.latinName = latinName;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

How do I create an instance a Bean?

package org.kodejava.example.bean;

import java.io.Serializable;
import java.io.IOException;
import java.beans.Beans;

public class TheBean implements Serializable {
    private Long id;
    private String name;

    public TheBean() {
    }

    public static void main(String[] args) {
        try {
            TheBean bean = (TheBean) Beans.instantiate(
                    ClassLoader.getSystemClassLoader(), "org.kodejava.example.bean.TheBean");
            System.out.println("The Bean = " + bean);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString() {
        return "[id=" + id + "; name=" + name + "]";
    }
}

How do I listen for a constrained property change?

The constrained property change is fired when a bean’s value is about to change. When a VetoableChangeListener veto the value change the bean’s value will be rolled-back to the previous value. In this example we have a constrained property called interest.

package org.kodejava.example.bean;

import java.beans.VetoableChangeSupport;
import java.beans.PropertyVetoException;

public class VetoBean {
    private double interest;

    private VetoableChangeSupport vcs = new VetoableChangeSupport(this);

    public VetoBean() {
        vcs.addVetoableChangeListener(new VetoChangeListener());
    }

    public double getInterest() {
        return interest;
    }

    public void setInterest(double interest) {
        try {
            vcs.fireVetoableChange("interest", new Double(this.interest), new Double(interest));

            this.interest = interest;
        } catch (PropertyVetoException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        VetoBean bean = new VetoBean();
        bean.setInterest(10.99);
        bean.setInterest(15.99);
        
        //
        // PropertyVetoException will be thrown beacuse the interest value 
        // should not exceed 20.00.
        //
        bean.setInterest(20.99);
    }
}
package org.kodejava.example.bean;

import java.beans.VetoableChangeListener;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyVetoException;

public class VetoChangeListener implements VetoableChangeListener {
    /**
     * This method gets called when a constrained property is changed.
     *
     * @param evt a PropertyChangeEvent object describing the
     *            event source and the property that has changed.
     * @throws java.beans.PropertyVetoException
     *          if the recipient wishes the property
     *          change to be rolled back.
     */
    public void vetoableChange(PropertyChangeEvent evt) throws PropertyVetoException {
        String eventName = evt.getPropertyName();
        if (eventName.equalsIgnoreCase("interest")) {
            double interest = ((Double) evt.getNewValue()).doubleValue();
            if (interest > 20.00) {
                throw new PropertyVetoException("Interest must be below 20.00", evt);                
            }
            System.out.println("Interest applied = " + interest);
        }
    }
}