Spring, первое приложение

import java.beans.PropertyVetoException;
import java.io.Serializable;
import java.beans.PropertyChangeSupport;
 
public class Main {
    public static void main(String[] args) {
 
        Purchase purch = new Purchase("komputer", "nie ma promocji", 3000.00);
        System.out.println(purch);
 
 
        class Purchase implements Serializable{
            private PropertyChangeSupport changes = new PropertyChangeSupport(this);
 
        }
 
        try {
            purch.setData("w promocji");
            purch.setPrice(2000.00);
            System.out.println(purch);
 
            purch.setPrice(500.00);
 
        } catch (PropertyVetoException exc) {
            System.out.println(exc.getMessage());
        }
        System.out.println(purch);
    }
}

import java.beans.PropertyVetoException;
import java.io.Serializable;
 
public class Purchase implements Serializable {
 
    private String prod;
    private String data;
    private double price;
 
    public Purchase(String prod, String data, double price) {
        this.prod = prod;
        this.data = data;
        this.price = price;
    }
 
    public void setData(final String data) throws PropertyVetoException {
        System.out.println("Change value of: data from: " + this.data + " to: " + data);
        this.data = data;
    }
 
    public void setProd(final String prod) {
        this.prod = prod;
    }
 
 
 
    public void setPrice(final double price) throws PropertyVetoException {
        if (price <= 1000) {
            try {
                throw new Exception();
            } catch (Exception e) {
                System.out.println("Price change to: " + price + " not allowed");
            }
        }
        else {
            System.out.println("Change value of: price from: " + this.price + " to: " + price);
            this.price = price;
        }
    }
 
    @Override
    public String toString() {
        return "Purchase [" + "prod=" + this.prod + ", data=" + this.data + ", price=" + this.price + ']';
    }
 
}