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 <header>
 
 <time datetime="2021-06-03T22:31:58+09:00">2021-06-03</time> by Dennis in 
&nbsp;<a href="/categories/tech" rel="category tag">tech</a>


&nbsp;<a href="/tags/java" rel="tag">java</a>, <a href="/tags/design-pattern" rel="tag">Design Pattern</a>


 </header>
 (Java 디자인 패턴 스터디 모집 중 : <a href="https://github.com/bluedskim/javaDesignPatterns">https://github.com/bluedskim/javaDesignPatterns</a>)
<h2 id="decorator-패턴">Decorator 패턴</h2>
<img src="https://stefanhenneken.files.wordpress.com/2019/02/picture03.png" alt="IEC 61131-3: The Decorator Pattern" title="IEC 61131-3: The Decorator Pattern">
(출처:<a href="https://stefanhenneken.net/2019/02/16/iec-61131-3-the-decorator-pattern">https://stefanhenneken.net/2019/02/16/iec-61131-3-the-decorator-pattern</a>)
<h2 id="해결하려는-문제">해결하려는 문제</h2>
<h2 id="특징용도">특징/용도</h2>
<ol>
<li>런타임에 객체에 동적으로 기능을 추가하기 위한 structural 패턴</li>
<li>래퍼wrapper 클래스로 구현.</li>
<li>chain of responsibility pattern과 유사함</li>
<li>생성자 혹은 다른 메소드에서 해당 클래스 자체를 인수로 받는 경우 데코레이터라 볼 수 있다(<a href="https://refactoring.guru/design-patterns/decorator/java/example">https://refactoring.guru/design-patterns/decorator/java/example</a>)</li>
</ol>
<h2 id="고려사항">고려사항</h2>
<h2 id="클래스-다이어그램">클래스 다이어그램</h2>
<img src="https://www.plantuml.com/plantuml/png/dLJ1IWCn53oRhmW5QNjeUoyUYgtefI3e3sIJvsxiPhFalHL41ONU5CIZe9uzAdZnbshz1wEsMxVTLd5FksycCybCs0wIS9IPcFT0MYV8Elv-zVW-VAcDNi_Vhc_7m_iwOv5MmC6aTCmDc00S5aSKMOMCaQOOLYf581Gu7X6bs6wrGarH5ZIbDQqWpa3XG9lMeJWIFK0T9hk225o2xC1Q_yB73pVZuVFuycxqTC7NbI2eLOxzq-ptcqfLUNLdfsrCnMzO14XEIE8o5eXy4ux0YH0s1G8_OMkfytgIGF4zSZe9kGAKJgUaRUBHB8Yrd48XK6-6rkevddiewmVmIUnQ9CyuOspY6mivs0VnvVczQZbv2rC7YFPFv6q7aFokF9T3roPA6qW8yv8M8oc45Km-PixTo4eR--npiHzxM0HhfNBrFnonh-D1cKTX_d_vlImKhao_2Fp7eB1auxJHo2z22JIjlGIQbbm2BMboZhc2o9RTXM_vXHvNymkThAOMusKTI9J__tm0" alt="Decorator 패턴(김동석)" title="Decorator 패턴(김동석)">
<h2 id="소스">소스</h2>
<ul>
<li>꾸며질decorated 객체
<ul>
<li>BeverageBase.java : 부모 abstract 객체
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;
abstract class BeverageBase {

	protected String description = "";

	public String getDescription() {
		return description;
	}

	/**
	 * 가격을 계산하는 로직은 하위 객체가 구현해야 한다.
	 * @return
	 */
	public abstract double getCost();
}</code></pre></td></tr></tbody></table>
</div></li>
<li>BlackTea.java
<div>
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<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

class BlackTea extends BeverageBase {

	public BlackTea() {
		description = "Black tea from teabag";
	}

	@Override
	public double getCost() {
		return 5;
	}
}</code></pre></td></tr></tbody></table>
</div></li>
<li>Espresso.java
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

abstract class BeverageBase {

	protected String description = "";

	public String getDescription() {
		return description;
	}

	/**
	 * 가격을 계산하는 로직은 하위 객체가 구현해야 한다.
	 * @return
	 */
	public abstract double getCost();
}</code></pre></td></tr></tbody></table>
</div></li>
<li>GreenTea.java
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

class GreenTea extends BeverageBase {

	public GreenTea() {
		description = "Green leaf tea";
	}

	@Override
	public double getCost() {
		return 8;
	}
}</code></pre></td></tr></tbody></table>
</div></li>
</ul>
</li>
<li>꾸미는decorator 객체
<ul>
<li>CondimentsDecoratorBase.java : 부모 abstract 객체
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

/**
 * 데코레이터 객체
 */
abstract class CondimentsDecoratorBase extends BeverageBase {
	BeverageBase beverage;

	/**
	 * 생성자에서 BeverageBase의 참조를 받아서 멤버변수에 할당
	 * @param beverage
	 */
	protected CondimentsDecoratorBase(BeverageBase beverage) {
		this.beverage = beverage;
	}
}</code></pre></td></tr></tbody></table>
</div></li>
<li>CholateCondiment.java
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

class ChocolateCondiment extends CondimentsDecoratorBase {
	/**
	 * 생성자에서 해당 클래스 자체를 인수로 받는다
	 */
	public ChocolateCondiment(BeverageBase beverage) {
		super(beverage);
		description = beverage.getDescription() + " + Chocolate";
	}

	@Override
	public double getCost() {
		return beverage.getCost() + 4;
	}
}</code></pre></td></tr></tbody></table>
</div></li>
<li>MilkCondiment.java
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

class MilkCondiment extends CondimentsDecoratorBase {
	public MilkCondiment(BeverageBase beverage) {
		super(beverage);
		description = this.beverage.getDescription() + " + Milk";
	}

	@Override
	public double getCost() {
		return beverage.getCost() + 3;
	}
}</code></pre></td></tr></tbody></table>
</div></li>
<li>SugarCondiment.java
<div>
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</code></pre></td>
<td>
<pre><code data-lang="java">package net.dskim.desingpattern.decorator;

class SugarCondiment extends CondimentsDecoratorBase {
	public SugarCondiment(BeverageBase beverage) {
		super(beverage);
		description = beverage.getDescription() + " + Sugar";
	}

	@Override
	public double getCost() {
		return beverage.getCost() + 1;
	}
}</code></pre></td></tr></tbody></table>
</div></li>
</ul>
</li>
</ul>
<h2 id="참고">참고</h2>
<ul>
<li><a href="https://www.baeldung.com/java-decorator-pattern">baeldung : The Decorator Pattern in Java</a></li>
<li><a href="https://dzone.com/articles/decorator-design-pattern-in-java">DZone : Decorator Design Pattern in Java</a></li>
</ul>


 

 
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</article> 



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Do What You Want To Do

(Java 디자인 패턴 스터디 모집 중 : https://github.com/bluedskim/javaDesignPatterns) Decorator 패턴 (출처:https://stefanhenneken.net/2019/02/16/iec-61131-3

Java 디자인 패턴-11.Decorator

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