如何用JSF2处理多态？

// 父类
public abstract class Animal {
    public abstract String makeSound();
}

// 子类
public class Dog extends Animal {
    @Override
    public String makeSound() {
        return "Woof!";
    }
}

public class Cat extends Animal {
    @Override
    public String makeSound() {
        return "Meow!";
    }
}

// JSF2 Managed Bean
@ManagedBean
public class AnimalBean {
    private Animal animal;

    public AnimalBean() {
        // 初始化animal为Dog对象
        animal = new Dog();
    }

    public Animal getAnimal() {
        return animal;
    }

    public void setAnimal(Animal animal) {
        this.animal = animal;
    }
}

<h:outputText value="#{animalBean.animal.makeSound()}" />