Comment faire pour télécharger des vidéos de youtube sur java?

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.io.Writer;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
import java.util.logging.Formatter;
import java.util.logging.Handler;
import java.util.logging.Level;
import java.util.logging.LogRecord;
import java.util.logging.Logger;
import java.util.regex.Pattern;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.CookieStore;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.ClientContext;
import org.apache.http.client.utils.URIUtils;
import org.apache.http.client.utils.URLEncodedUtils;
import org.apache.http.impl.client.BasicCookieStore;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.BasicHttpContext;
import org.apache.http.protocol.HttpContext;
public class JavaYoutubeDownloader {
public static String newline = System.getProperty("line.separator");
private static final Logger log = Logger.getLogger(JavaYoutubeDownloader.class.getCanonicalName());
private static final Level defaultLogLevelSelf = Level.FINER;
private static final Level defaultLogLevel = Level.WARNING;
private static final Logger rootlog = Logger.getLogger("");
private static final String scheme = "http";
private static final String host = "www.youtube.com";
private static final Pattern commaPattern = Pattern.compile(",");
private static final Pattern pipePattern = Pattern.compile("\\|");
private static final char[] ILLEGAL_FILENAME_CHARACTERS = { '/', '\n', '\r', '\t', '\0', '\f', '`', '?', '*', '\\', '<', '>', '|', '\"', ':' };
private static void usage(String error) {
if (error != null) {
System.err.println("Error: " + error);
}
System.err.println("usage: JavaYoutubeDownload VIDEO_ID DESTINATION_DIRECTORY");
System.exit(-1);
}
public static void main(String[] args) {
if (args == null || args.length == 0) {
usage("Missing video id. Extract from http://www.youtube.com/watch?v=VIDEO_ID");
}
try {
setupLogging();
log.fine("Starting");
String videoId = null;
String outdir = ".";
//TODO Ghetto command line parsing
if (args.length == 1) {
videoId = args[0];
} else if (args.length == 2) {
videoId = args[0];
outdir = args[1];
}
int format = 18; //http://en.wikipedia.org/wiki/YouTube#Quality_and_codecs
String encoding = "UTF-8";
String userAgent = "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.13) Gecko/20101203 Firefox/3.6.13";
File outputDir = new File(outdir);
String extension = getExtension(format);
play(videoId, format, encoding, userAgent, outputDir, extension);
} catch (Throwable t) {
t.printStackTrace();
}
log.fine("Finished");
}
private static String getExtension(int format) {
//TODO
return "mp4";
}
private static void play(String videoId, int format, String encoding, String userAgent, File outputdir, String extension) throws Throwable {
log.fine("Retrieving " + videoId);
List<NameValuePair> qparams = new ArrayList<NameValuePair>();
qparams.add(new BasicNameValuePair("video_id", videoId));
qparams.add(new BasicNameValuePair("fmt", "" + format));
URI uri = getUri("get_video_info", qparams);
CookieStore cookieStore = new BasicCookieStore();
HttpContext localContext = new BasicHttpContext();
localContext.setAttribute(ClientContext.COOKIE_STORE, cookieStore);
HttpClient httpclient = new DefaultHttpClient();
HttpGet httpget = new HttpGet(uri);
httpget.setHeader("User-Agent", userAgent);
log.finer("Executing " + uri);
HttpResponse response = httpclient.execute(httpget, localContext);
HttpEntity entity = response.getEntity();
if (entity != null && response.getStatusLine().getStatusCode() == 200) {
InputStream instream = entity.getContent();
String videoInfo = getStringFromInputStream(encoding, instream);
if (videoInfo != null && videoInfo.length() > 0) {
List<NameValuePair> infoMap = new ArrayList<NameValuePair>();
URLEncodedUtils.parse(infoMap, new Scanner(videoInfo), encoding);
String token = null;
String downloadUrl = null;
String filename = videoId;
for (NameValuePair pair : infoMap) {
String key = pair.getName();
String val = pair.getValue();
log.finest(key + "=" + val);
if (key.equals("token")) {
token = val;
} else if (key.equals("title")) {
filename = val;
} else if (key.equals("fmt_url_map")) {
String[] formats = commaPattern.split(val);
for (String fmt : formats) {
String[] fmtPieces = pipePattern.split(fmt);
if (fmtPieces.length == 2) {
//in the end, download somethin!
downloadUrl = fmtPieces[1];
int pieceFormat = Integer.parseInt(fmtPieces[0]);
if (pieceFormat == format) {
//found what we want
downloadUrl = fmtPieces[1];
break;
}
}
}
}
}
filename = cleanFilename(filename);
if (filename.length() == 0) {
filename = videoId;
} else {
filename += "_" + videoId;
}
filename += "." + extension;
File outputfile = new File(outputdir, filename);
if (downloadUrl != null) {
downloadWithHttpClient(userAgent, downloadUrl, outputfile);
}
}
}
}
private static void downloadWithHttpClient(String userAgent, String downloadUrl, File outputfile) throws Throwable {
HttpGet httpget2 = new HttpGet(downloadUrl);
httpget2.setHeader("User-Agent", userAgent);
log.finer("Executing " + httpget2.getURI());
HttpClient httpclient2 = new DefaultHttpClient();
HttpResponse response2 = httpclient2.execute(httpget2);
HttpEntity entity2 = response2.getEntity();
if (entity2 != null && response2.getStatusLine().getStatusCode() == 200) {
long length = entity2.getContentLength();
InputStream instream2 = entity2.getContent();
log.finer("Writing " + length + " bytes to " + outputfile);
if (outputfile.exists()) {
outputfile.delete();
}
FileOutputStream outstream = new FileOutputStream(outputfile);
try {
byte[] buffer = new byte[2048];
int count = -1;
while ((count = instream2.read(buffer)) != -1) {
outstream.write(buffer, 0, count);
}
outstream.flush();
} finally {
outstream.close();
}
}
}
private static String cleanFilename(String filename) {
for (char c : ILLEGAL_FILENAME_CHARACTERS) {
filename = filename.replace(c, '_');
}
return filename;
}
private static URI getUri(String path, List<NameValuePair> qparams) throws URISyntaxException {
URI uri = URIUtils.createURI(scheme, host, -1, "/" + path, URLEncodedUtils.format(qparams, "UTF-8"), null);
return uri;
}
private static void setupLogging() {
changeFormatter(new Formatter() {
@Override
public String format(LogRecord arg0) {
return arg0.getMessage() + newline;
}
});
explicitlySetAllLogging(Level.FINER);
}
private static void changeFormatter(Formatter formatter) {
Handler[] handlers = rootlog.getHandlers();
for (Handler handler : handlers) {
handler.setFormatter(formatter);
}
}
private static void explicitlySetAllLogging(Level level) {
rootlog.setLevel(Level.ALL);
for (Handler handler : rootlog.getHandlers()) {
handler.setLevel(defaultLogLevelSelf);
}
log.setLevel(level);
rootlog.setLevel(defaultLogLevel);
}
private static String getStringFromInputStream(String encoding, InputStream instream) throws UnsupportedEncodingException, IOException {
Writer writer = new StringWriter();
char[] buffer = new char[1024];
try {
Reader reader = new BufferedReader(new InputStreamReader(instream, encoding));
int n;
while ((n = reader.read(buffer)) != -1) {
writer.write(buffer, 0, n);
}
} finally {
instream.close();
}
String result = writer.toString();
return result;
}
}
/**
* <pre>
* Exploded results from get_video_info:
* 
* fexp=90...
* allow_embed=1
* fmt_stream_map=35|http://v9.lscache8...
* fmt_url_map=35|http://v9.lscache8...
* allow_ratings=1
* keywords=Stefan Molyneux,Luke Bessey,anarchy,stateless society,giant stone cow,the story of our unenslavement,market anarchy,voluntaryism,anarcho capitalism
* track_embed=0
* fmt_list=35/854x480/9/0/115,34/640x360/9/0/115,18/640x360/9/0/115,5/320x240/7/0/0
* author=lukebessey
* muted=0
* length_seconds=390
* plid=AA...
* ftoken=null
* status=ok
* watermark=http://s.ytimg.com/yt/swf/logo-vfl_bP6ud.swf,http://s.ytimg.com/yt/swf/hdlogo-vfloR6wva.swf
* timestamp=12...
* has_cc=False
* fmt_map=35/854x480/9/0/115,34/640x360/9/0/115,18/640x360/9/0/115,5/320x240/7/0/0
* leanback_module=http://s.ytimg.com/yt/swfbin/leanback_module-vflJYyeZN.swf
* hl=en_US
* endscreen_module=http://s.ytimg.com/yt/swfbin/endscreen-vflk19iTq.swf
* vq=auto
* avg_rating=5.0
* video_id=S6IZP3yRJ9I
* token=vPpcFNh...
* thumbnail_url=http://i4.ytimg.com/vi/S6IZP3yRJ9I/default.jpg
* title=The Story of Our Unenslavement - Animated
* </pre>
*/

Vous pouvez voir ce que l'API est exposée ici

ytd2 , c'est un téléchargeur de vidéo YouTube. Découvrez son code source si vous voulez voir comment c'est fait.