《大话设计模式》--装饰者模式

题目：给一个人“小王”搭配衣服和裤子

public abstract class Component {
    public abstract void operation();
}

public class ConcreteComponent extends Component {
    @Override
    public void operation() {
        System.out.println("具体对象的操作");
    }
}

public abstract class Decorator extends Component {

    protected Component component;

    public void setComponent(Component component) {
        this.component = component;
    }

    @Override
    public void operation() {
        if (component != null) {
            component.operation();
        }
    }
}

public class ConcreteDecoratorA extends Decorator {
    private String addedState;

    @Override
    public void operation() {
        super.operation();
        addedState = "New State";
        System.out.println("具体装饰对象A的操作");
    }
}

public class ConcreteDecoratorB extends Decorator {
    @Override
    public void operation() {
        super.operation();
        addBehavior();
        System.out.println("具体装饰对象B的操作");
    }

    private void addBehavior() {

    }
}

public class Wear {
    public static void main(String args[]){
        ConcreteComponent c = new ConcreteComponent();
        ConcreteDecoratorA d1 = new ConcreteDecoratorA();
        ConcreteDecoratorB d2 = new ConcreteDecoratorB();
        d1.setComponent(c);
        d2.setComponent(d1);
        d2.operation();
    }
}

特别注意这段

        d1.setComponent(c);
        d2.setComponent(d1);
        d2.operation();

一层套一层，代表功能的拓展

装饰者模式是利用setComponent进行包装的

另外，如果只有一个ConcreteComponent类而没有抽象的Component类，那Decorator类可以是ConcreteComponent的一个子类。

如果只有一个ConcreteDecorator类，那么就没有必要建立一个单独的Decorator类，而可以把Decorator和ConcreteDecorator的责任合并成一个类。

public class Person {
    private String name;

    public Person() {
    }

    public Person(String name) {
        this.name = name;
    }

    public void show() {
        System.out.println("装扮的" + name);
    }
}

public class Decorator extends Person {

    protected Person component;

    public void Decorator(Person component) {
        this.component = component;
    }

    @Override
    public void show() {
        if (component != null) {
            component.show();
        }
    }
}

public class TShirt extends Decorator {

    @Override
    public void show() {
        System.out.println("大T恤");
        super.show();
    }
}

public class BigTrouser extends Decorator {

    @Override
    public void show() {
        System.out.println("垮裤");
        super.show();
    }
}

public class Wear {
    public static void main(String args[]) {
        Person person = new Person("小王");
        TShirt tShirt = new TShirt();
        BigTrouser bigTrouser = new BigTrouser();

        tShirt.Decorator(person);
        bigTrouser.Decorator(tShirt);
        bigTrouser.show();
    }
}

tShirt.Decorator(person);

bigTrouser.Decorator(tShirt);

bigTrouser.show();

就是装饰过程