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装饰模式

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通过使用修饰模式，可以在运行时扩充一个类别的功能。原理是：增加一个修饰类包裹原来的类别，包裹的方式是在修饰类的构造函数中将原来的类以参数的形式传入。装饰类实现新的功能，但是，在不需要用到新功能的地方，它可以直接调用原来的类别中的方法。修饰类必须和原来的类别有相同的接口。

装饰器

UML类图

decorator_uml

代码实现

Component类

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package com.lei.designpatterns.decorator;

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

ConcreteComponent类

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package com.lei.designpatterns.decorator;

public class ConcreteComponent extends Component{

    @Override
    public void operation() {
        System.out.println("Concrete component.");
    }
}

Decorator类

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package com.lei.designpatterns.decorator;

public class Decorator extends Component{
    protected Component component;

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

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

ConcreteDecoratorA类

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package com.lei.designpatterns.decorator;

public class ConcreteDecoratorA extends Decorator{
    private String addedState;

    @Override
    public void operation() {
        super.operation();
        this.addedState = "New state.";
        System.out.println("New Operation a.");
    }
}

ConcreteDecoratorB

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package com.lei.designpatterns.decorator;

public class ConcreteDecoratorB extends Decorator{
    @Override
    public void operation() {
        super.operation();
        addedBehavior();
        System.out.println("New Operation b.");
    }

    private void addedBehavior(){
    }
}

装饰器样例

UML类图

decorator_example_uml

代码实现

Person类

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package com.lei.designpatterns.decorator;

public class Person {
    private String name;

    public Person(){
    }

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

    public void show(){
        System.out.println("Show.");
    }
}

Finery类

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package com.lei.designpatterns.decorator;

public class Finery extends Person{
    private Person component;

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

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

TShirts类

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package com.lei.designpatterns.decorator;

public class TShirts extends Finery {
    @Override
    public void show() {
        System.out.println("T shirts.");
        super.show();
    }
}

BigTrouser类

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package com.lei.designpatterns.decorator;

public class BigTrouser extends Finery {
    @Override
    public void show() {
        System.out.println("Big trouser.");
        super.show();
    }
}

BrokenSneaker类

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package com.lei.designpatterns.decorator;

public class BrokenSneaker extends Finery {
    @Override
    public void show() {
        System.out.println("Broken sneaker.");
        super.show();
    }
}

Suite类

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package com.lei.designpatterns.decorator;

public class Suite extends Finery {
    @Override
    public void show() {
        System.out.println("Suite.");
        super.show();
    }
}

Tie类

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package com.lei.designpatterns.decorator;

public class Tie extends Finery {
    @Override
    public void show() {
        System.out.println("Tie.");
        super.show();
    }
}

LeatherShoes类

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package com.lei.designpatterns.decorator;

public class LeatherShoes extends Finery {
    @Override
    public void show() {
        System.out.println("Leather shoes.");
        super.show();
    }
}