[JAVA] 디자인 패턴 - Proxy

Proxy Pattern

• 대리인 이라는 뜻으로, 뭔가를 대신해서 처리하는 것이다.
• Proxy Class를 통해서 대신 전달하는 형태로 설계되며, 실제 Client는 Proxy로 부터 결과를 받는다.
• Cache의 기능으로도 활용이 가능하다.
• SOLID중에서 개방폐쇄 원칙(OCP)과 의존 역전 원칙(DIP)를 따른다.

Html.java

public class Html {
    private String url;

    public Html(String url) {
        this.url = url;
    }
}

IBrowser.java

public interface IBrowser {
    Html show();
}

Browser.java

public class Browser implements IBrowser {
    private String url;

    public Browser(String url) {
        this.url = url;
    }

    @Override
    public Html show() {
        System.out.println("browser loading html from : " + url);
        return new Html(url);
    }
}

BrowserProxy.java

public class BrowserProxy implements IBrowser {
    private String url;
    private Html html;

    public BrowserProxy(String url) {
        this.url = url;
    }

    @Override
    public Html show() {
        if (html == null) {
            this.html = new Html(url);
            System.out.println("BrowserProxy loading html form : " + url);
        }

        System.out.println("BrowserProxy use cache html : " + url);
        return html;
    }
}

AopBrowser.java

import com.example.demo.proxy.Html;
import com.example.demo.proxy.IBrowser;

public class AopBrowser implements IBrowser {
    private String url;
    private Html html;
    private Runnable before;
    private Runnable after;

    public AopBrowser(String url, Runnable before, Runnable after){
        this.url = url;
        this.before = before;
        this.after = after;
    }

    @Override
    public Html show(){
        before.run();

        if(html == null){
            this.html = new Html(url);
            System.out.println("AopBrowser html loading from : " + url);

            try {
                Thread.sleep(1500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        after.run();

        System.out.println("AopBrowser html cache : " + url);
        return null;
    }
}

DemoApplication.java

import com.example.demo.aop.AopBrowser;
import org.springframework.boot.autoconfigure.SpringBootApplication;

import java.util.concurrent.atomic.AtomicLong;

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        Browser browser = new Browser("www.naver.com");
        browser.show();
        browser.show();

        System.out.println("");

        IBrowser browser1 = new BrowserProxy("www.daum.net");
        browser1.show();
        browser1.show();

        System.out.println("");

        AtomicLong start = new AtomicLong();
        AtomicLong end = new AtomicLong();

        IBrowser aopBrowser = new AopBrowser("www.google.com", () -> {
            System.out.println("before");
            start.set(System.currentTimeMillis());
        }, () -> {
            long now = System.currentTimeMillis();
            end.set(now - start.get());
        });

        aopBrowser.show();
        System.out.println("loading time : " + end.get());
        aopBrowser.show();
        System.out.println("loading time : " + end.get());
    }
}

 

스프링 AOP

• 프록시 기반의 AOP 구현체이며, 스프링 Bean에만 AOP 적용 가능하다.