Java: Proxy

Proxy
More about Proxy

Application of the pattern in Java

Complexity:

Popularity:

Example: Caching proxy

some_cool_media_library

some_cool_media_library/ThirdPartyYoutubeLib.java: Remote service interface

package refactoring_guru.patterns.proxy.example.some_cool_media_library;

import java.util.HashMap;

public interface ThirdPartyYoutubeLib {
    public HashMap<String, Video> popularVideos();

    public Video getVideo(String videoId);
}

some_cool_media_library/ThirdPartyYoutubeLib.java: Remote service implementation

package refactoring_guru.patterns.proxy.example.some_cool_media_library;

import java.util.HashMap;

public interface ThirdPartyYoutubeLib {
    public HashMap<String, Video> popularVideos();

    public Video getVideo(String videoId);
}

some_cool_media_library/Video.java: Video file

package refactoring_guru.patterns.proxy.example.some_cool_media_library;

public class Video {
    public String id;
    public String title;
    public String data;

    public Video(String id, String title) {
        this.id = id;
        this.title = title;
        this.data = "Random video.";
    }
}

proxy

proxy/YoutubeCacheProxy.java: Caching proxy

package refactoring_guru.patterns.proxy.example.proxy;

import refactoring_guru.patterns.proxy.example.some_cool_media_library.ThirdPartyYoutubeClass;
import refactoring_guru.patterns.proxy.example.some_cool_media_library.ThirdPartyYoutubeLib;
import refactoring_guru.patterns.proxy.example.some_cool_media_library.Video;

import java.util.HashMap;

public class YoutubeCacheProxy implements ThirdPartyYoutubeLib {
    private ThirdPartyYoutubeLib youtubeService;
    private HashMap<String, Video> cachePopular = new HashMap<String, Video>();
    private HashMap<String, Video> cacheAll = new HashMap<String, Video>();

    public YoutubeCacheProxy() {
        this.youtubeService = new ThirdPartyYoutubeClass();
    }

    @Override
    public HashMap<String, Video> popularVideos() {
        if (cachePopular.isEmpty()) {
            cachePopular = youtubeService.popularVideos();
        } else {
            System.out.println("Retrieved list from cache.");
        }
        return cachePopular;
    }

    @Override
    public Video getVideo(String videoId) {
        Video video = cacheAll.get(videoId);
        if (video == null) {
            video = youtubeService.getVideo(videoId);
            cacheAll.put(videoId, video);
        } else {
            System.out.println("Retrieved video '" + videoId + "' from cache.");
        }
        return video;
    }

    public void reset() {
        cachePopular.clear();
        cacheAll.clear();
    }
}

downloader

downloader/YoutubeDownloader.java: Media downloader app

package refactoring_guru.patterns.proxy.example.downloader;

import refactoring_guru.patterns.proxy.example.some_cool_media_library.ThirdPartyYoutubeLib;
import refactoring_guru.patterns.proxy.example.some_cool_media_library.Video;

import java.util.HashMap;

public class YoutubeDownloader {
    private ThirdPartyYoutubeLib api;

    public YoutubeDownloader(ThirdPartyYoutubeLib api) {
        this.api = api;
    }

    public void renderVideoPage(String videoId) {
        Video video = api.getVideo(videoId);
        System.out.println("\n-------------------------------");
        System.out.println("Video page (imagine fancy HTML)");
        System.out.println("ID: " + video.id);
        System.out.println("Title: " + video.title);
        System.out.println("Video: " + video.data);
        System.out.println("-------------------------------\n");
    }

    public void renderPopularVideos() {
        HashMap<String, Video> list = api.popularVideos();
        System.out.println("\n-------------------------------");
        System.out.println("Most popular videos on Youtube (imagine fancy HTML)");
        for (Video video : list.values()) {
            System.out.println("ID: " + video.id + " / Title: " + video.title);
        }
        System.out.println("-------------------------------\n");
    }
}

Demo.java: Initialization code

package refactoring_guru.patterns.proxy.example;

import refactoring_guru.patterns.proxy.example.downloader.YoutubeDownloader;
import refactoring_guru.patterns.proxy.example.proxy.YoutubeCacheProxy;
import refactoring_guru.patterns.proxy.example.some_cool_media_library.ThirdPartyYoutubeClass;

public class Demo {

    public static void main(String[] args) {
        YoutubeDownloader naiveDownloader = new YoutubeDownloader(new ThirdPartyYoutubeClass());
        YoutubeDownloader smartDownloader = new YoutubeDownloader(new YoutubeCacheProxy());

        long naive = test(naiveDownloader);
        long smart = test(smartDownloader);
        System.out.print("Time saved by caching proxy: " + (naive - smart) + "ms");

    }

    public static long test(YoutubeDownloader downloader) {
        long startTime = System.currentTimeMillis();

        // User behavior in our app:
        downloader.renderPopularVideos();
        downloader.renderVideoPage("catzzzzzzzzz");
        downloader.renderPopularVideos();
        downloader.renderVideoPage("dancesvideoo");
        // Looks like out users visit same pages very often.
        downloader.renderVideoPage("catzzzzzzzzz");
        downloader.renderVideoPage("someothervid");

        long estimatedTime = System.currentTimeMillis() - startTime;
        System.out.print("Time elapsed: " + estimatedTime + "ms\n");
        return estimatedTime;
    }
}

OutputDemo.txt: Execution result

Connecting to http://www.youtube.com... Connected!
Downloading populars... Done!

-------------------------------
Most popular videos on Youtube (imagine fancy HTML)
ID: sadgahasgdas / Title: Catzzzz.avi
ID: 3sdfgsd1j333 / Title: Programing lesson#1.avi
ID: mkafksangasj / Title: Dog play with ball.mp4
ID: dlsdk5jfslaf / Title: Barcelona vs RealM.mov
ID: asdfas3ffasd / Title: Dancing video.mpq
-------------------------------

Connecting to http://www.youtube.com/catzzzzzzzzz... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: catzzzzzzzzz
Title: Some video title
Video: Random video.
-------------------------------

Connecting to http://www.youtube.com... Connected!
Downloading populars... Done!

-------------------------------
Most popular videos on Youtube (imagine fancy HTML)
ID: sadgahasgdas / Title: Catzzzz.avi
ID: 3sdfgsd1j333 / Title: Programing lesson#1.avi
ID: mkafksangasj / Title: Dog play with ball.mp4
ID: dlsdk5jfslaf / Title: Barcelona vs RealM.mov
ID: asdfas3ffasd / Title: Dancing video.mpq
-------------------------------

Connecting to http://www.youtube.com/dancesvideoo... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: dancesvideoo
Title: Some video title
Video: Random video.
-------------------------------

Connecting to http://www.youtube.com/catzzzzzzzzz... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: catzzzzzzzzz
Title: Some video title
Video: Random video.
-------------------------------

Connecting to http://www.youtube.com/someothervid... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: someothervid
Title: Some video title
Video: Random video.
-------------------------------

Time elapsed: 9901ms
Connecting to http://www.youtube.com... Connected!
Downloading populars... Done!

-------------------------------
Most popular videos on Youtube (imagine fancy HTML)
ID: sadgahasgdas / Title: Catzzzz.avi
ID: 3sdfgsd1j333 / Title: Programing lesson#1.avi
ID: mkafksangasj / Title: Dog play with ball.mp4
ID: dlsdk5jfslaf / Title: Barcelona vs RealM.mov
ID: asdfas3ffasd / Title: Dancing video.mpq
-------------------------------

Connecting to http://www.youtube.com/catzzzzzzzzz... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: catzzzzzzzzz
Title: Some video title
Video: Random video.
-------------------------------

Retrieved list from cache.

-------------------------------
Most popular videos on Youtube (imagine fancy HTML)
ID: sadgahasgdas / Title: Catzzzz.avi
ID: 3sdfgsd1j333 / Title: Programing lesson#1.avi
ID: mkafksangasj / Title: Dog play with ball.mp4
ID: dlsdk5jfslaf / Title: Barcelona vs RealM.mov
ID: asdfas3ffasd / Title: Dancing video.mpq
-------------------------------

Connecting to http://www.youtube.com/dancesvideoo... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: dancesvideoo
Title: Some video title
Video: Random video.
-------------------------------

Retrieved video 'catzzzzzzzzz' from cache.

-------------------------------
Video page (imagine fancy HTML)
ID: catzzzzzzzzz
Title: Some video title
Video: Random video.
-------------------------------

Connecting to http://www.youtube.com/someothervid... Connected!
Downloading video... Done!

-------------------------------
Video page (imagine fancy HTML)
ID: someothervid
Title: Some video title
Video: Random video.
-------------------------------

Time elapsed: 5991ms
Time saved by caching proxy: 3910ms