Youtube API + GAEJ + FreeMarker + Spring

I have developed very very simple youtube sample application on Google App Engine.
Internally I have used FreeMarker and Spring.

The purpose of this blog entry is just giving hints how to use Spring + FreeMarker on GAEJ with youtube API example.

Youtube API

Here is the code for extracting video url etc from Youtube API response.
I frequently use JDOM for parsing XML.

package com.dukesoftware.gaej.youtube;

import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.Namespace;
import org.jdom.input.SAXBuilder;
import org.jdom.xpath.XPath;

import com.dukesoftware.utils.io.JDOMUtils;
import com.dukesoftware.utils.io.MinimumIOUtils;

public class YouTube {

    private final static XPath XPATH_MEDIA;
    private final static Namespace NS_MEDIA = Namespace.getNamespace("http://search.yahoo.com/mrss/");
    static{
        try {
            XPATH_MEDIA = XPath.newInstance("/x:feed/x:entry/media:group");
            XPATH_MEDIA.addNamespace("x", "http://www.w3.org/2005/Atom");
        } catch (JDOMException e) {
            throw new RuntimeException("Exception during creating xpath", e);
        }
    }
    
    public static List<YoutubeElement> serachFromYoutube(String keyword,
            int max) throws URISyntaxException, IOException, JDOMException {
        URI uri = new URI("http", "gdata.youtube.com", "/feeds/api/videos", "q="+keyword+"&max-results="+max, null);
        String xmlStr = getStringContentsFromURL(uri.toASCIIString(), "utf-8");
        return toYoutubeElements(xmlStr);
    }

    private static List<YoutubeElement> toYoutubeElements(String xmlStr) throws JDOMException, IOException, URISyntaxException {
        Document doc = JDOMUtils.createDocument(new SAXBuilder(), xmlStr);
        return toYoutubeElements(doc);
    }

    private static List<YoutubeElement> toYoutubeElements(Document doc)
            throws JDOMException, URISyntaxException {
        List<YoutubeElement> youtubeElements = new ArrayList<YoutubeElement>();
        for(Element elem : (List<Element>)XPATH_MEDIA.selectNodes(doc)){
            URI playerUrl = new URI(elem.getChild("player", NS_MEDIA).getAttribute("url").getValue());
            
            URI thumbnailUrl = extractLargestThumbnailUrl(elem);
            
            String title = elem.getChild("title", NS_MEDIA).getValue();
            
            youtubeElements.add(
                    new YoutubeElement(
                            playerUrl, 
                            thumbnailUrl,
                            title == null ? "" : title)
                    );
        }
        return youtubeElements;
    }

    private static URI extractLargestThumbnailUrl(Element elem) throws URISyntaxException {
        List<Element> thumbnails = elem.getChildren("thumbnail", NS_MEDIA);
        String thumbnailUrl = null;
        if(!thumbnails.isEmpty()){
            thumbnailUrl = thumbnails.get(0).getAttribute("url").getValue();
        }
        return new URI(thumbnailUrl);
    }
    
    public static String getStringContentsFromURL(String u, String charset) throws URISyntaxException, IOException {
        URL url = new URL(u);
        HttpURLConnection connection = null;
        try{
            connection = (HttpURLConnection)url.openConnection();
            return MinimumIOUtils.toString(connection.getInputStream(), charset);
        }
        finally{
            disconnect(connection);
        }
    }
    
    public final static void disconnect(HttpURLConnection urlconn){
        if(urlconn != null){
            urlconn.disconnect();
        }
    }
}

This is just a kind of entity class for holoding extracted youtube information.

package com.dukesoftware.gaej.youtube;

import java.net.URI;

public class YoutubeElement {

    private final URI playerUrl;
    private final URI thumbnailUrl;
    private final String title;

    public YoutubeElement(URI playerUrl, URI thumbnailUrl, String title) {
        this.playerUrl = playerUrl;
        this.thumbnailUrl = thumbnailUrl;
        this.title = title;
    }

    public URI getPlayerUrl() {
        return playerUrl;
    }

    public URI getThumbnailUrl() {
        return thumbnailUrl;
    }

    public String getTitle() {
        return title;
    }
}

Freemarker

<!DOCTYPE html>
<html>
<head>
  <#if keyword??>
  <title>Youtube Video Search Results for '${keyword}'</title>
  <#else>
  <title>Youtube Video Search</title>
  </#if>
  <script src="//ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>
  <link rel="stylesheet" type="text/css" href="somecss.css" />
  <script type="text/javascript" src="somejavascript.js"></script>
</head>
<body>
  <div align="center">
  <#if keyword??>
  <strong> Video Search Results for '${keyword}'</strong>
  <#else>
  <strong> Search From Youtube!!</strong>
  </#if>
  </div>
  <br />
  
  <div align="center">
  <form action="/youtube/searchVideo" method="get">
      <input type="text" name="keyword" value="<#if keyword??>${keyword}</#if>"/>
      <input type="submit" value="search"/>
  </form>
  </div>

  <div align="center">  
  <ul class="column">
  <#list youtubeelements as youtubeelement>
  <li>
  <div class="block">
  <a href="${youtubeelement.playerUrl.toASCIIString()?html}"><img src="${youtubeelement.thumbnailUrl.toASCIIString()?html}" title="${youtubeelement.title?html}"/></a>
  </div>
  </li>
  </#list>
  </ul>
  </div>
</body>
</html>