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Facade Pattern
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Facade Pattern

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복잡한 과정을 간단하게 제공

Intent

Facade is a structural design pattern that provides a simplified interface to a library, a framework, or any other complex set of classes.

Implementation

notion image

Applicablity

  • 복잡한 Subsystem의 인터페이스를 제한하고 싶을때
  • Subsystem을 계층 구조로 나타내고 싶을때
 

Examples

javax.faces.context.ExternalContext uses ServletContext, HttpSession, HttpServletRequest, HttpServletResponse and others inside.
 

Code Exampl

 
Facade 가 package-private으로 정의된 HelpSystemN 클래스에 대한 입구를 제공해줌
 

Specific problems

  • Facade는 일반적으로 Singleton 으로 제공되는것이 좋다.
 
 
package oodesign.design.structural.facade.subsystem;

class HelpSystem01 {

    public HelpSystem01(){
        System.out.println("call constructor: "+getClass().getSimpleName());
    }

    public void proc(){
        System.out.println("call proc: "+getClass().getSimpleName());
    }
}

class HelpSystem02 {

    public HelpSystem02(){
        System.out.println("call constructor: "+getClass().getSimpleName());
    }

    public void proc(){
        System.out.println("call proc: "+getClass().getSimpleName());
    }
}

class HelpSystem03 {

    public HelpSystem03(){
        System.out.println("call constructor: "+getClass().getSimpleName());
    }

    public void proc(){
        System.out.println("call proc: "+getClass().getSimpleName());
    }
}

package oodesign.design.structural.facade.subsystem;

public class Facade {

    private HelpSystem01 helpSystem01;
    private HelpSystem02 helpSystem02;
    private HelpSystem03 helpSystem03;

    public Facade(){
        helpSystem01 = new HelpSystem01();
        helpSystem02 = new HelpSystem02();
        helpSystem03 = new HelpSystem03();
    }

    public void proc(){
        helpSystem01.proc();
        helpSystem02.proc();
        helpSystem03.proc();
    }
}

package oodesign.design.structural.facade;

public class Main {

    public static void main(String[] args) {
        new Facade().proc();
    }
}