Java中PropertyChangeListener的用法 详解属性变更

import java.beans.*;

public class MyBean {

    private String name;
    private PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    public String getName() {
        return name;
    }

    public void setName(String name) {
        String oldName = this.name;
        this.name = name;
        pcs.firePropertyChange("name", oldName, name);
    }

    public void addPropertyChangeListener(PropertyChangeListener listener) {
        pcs.addPropertyChangeListener(listener);
    }

    public void removePropertyChangeListener(PropertyChangeListener listener) {
        pcs.removePropertyChangeListener(listener);
    }

    public static void main(String[] args) {
        MyBean bean = new MyBean();

        bean.addPropertyChangeListener(evt -> {
            System.out.println("Property " + evt.getPropertyName() + " changed from " + evt.getOldValue() + " to " + evt.getNewValue());
        });

        bean.setName("Alice");
        bean.setName("Bob");
    }
}

import java.beans.*;

public class MyBeanWithVeto {

    private int age;
    private VetoableChangeSupport vcs = new VetoableChangeSupport(this);

    public int getAge() {
        return age;
    }

    public void setAge(int age) throws PropertyVetoException {
        vcs.fireVetoableChange("age", this.age, age);
        this.age = age;
    }

    public void addVetoableChangeListener(VetoableChangeListener listener) {
        vcs.addVetoableChangeListener(listener);
    }

    public void removeVetoableChangeListener(VetoableChangeListener listener) {
        vcs.removeVetoableChangeListener(listener);
    }

    public static void main(String[] args) {
        MyBeanWithVeto bean = new MyBeanWithVeto();

        bean.addVetoableChangeListener(evt -> {
            int newAge = (int) evt.getNewValue();
            if (newAge < 0) {
                throw new PropertyVetoException("Age cannot be negative", evt);
            }
        });

        try {
            bean.setAge(25);
            bean.setAge(-5); // 会抛出 PropertyVetoException
        } catch (PropertyVetoException e) {
            System.err.println("Vetoed: " + e.getMessage());
        }

        System.out.println("Age: " + bean.getAge());
    }
}