Google Picasa API初體驗

Google Picasa是一個在線的相冊系統，他提供了很多API，我們可以對相冊進行操作，下面就是一個簡單的獲得一個用戶所有相冊，並把相冊裏面所有的圖片顯示出來，頁面我也沒有做什麼美化，在初步研究之後，發現它的API的功能還比較強大，以後有時間了再看看其他的功能。源代碼和.war文件都太大了，上傳兩個圖片看看。。




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import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.gdata.client.photos.PicasawebService;
import com.google.gdata.data.Link;
import com.google.gdata.data.photos.AlbumEntry;
import com.google.gdata.data.photos.AlbumFeed;
import com.google.gdata.data.photos.GphotoEntry;
import com.google.gdata.data.photos.PhotoEntry;
import com.google.gdata.data.photos.UserFeed;
import com.google.gdata.util.AuthenticationException;
import com.google.gdata.util.ServiceException;

public class PicasaServlet extends HttpServlet {

    /**
     * This is a serial version generated by eclipse.
     */
    private static final long serialVersionUID = -6737329335179440491L;

    /**
     * This is the api prefix of the goold picasa forum.
     */
    private static final String API_PREFIX = "http://picasaweb.google.com/data/feed/api/user/";

    /**
     * This method is to deal with the HTTP GET request.
     *
     * @param request
     *            The HttPServletRequest object.
     * @param response
     *            The HttpServletResponse object.
     * @throws ServletException
     *             Throws servlet exception if encounters some server errors.
     * @throws IOException
     *             Throws IOException if encounter some io write/read errors.
     */
    @Override
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        doPost(request, response);
    }

    /**
     * This method is to deal with the HTTP Post request. Download the image and
     * corresponding thumbnails image with emailAddress and password
     * authentication, and save it to "/image" folder, this can be displayed
     * directly in the client.
     *
     * @param request
     *            The HttPServletRequest object.
     * @param response
     *            The HttpServletResponse object.
     * @throws ServletException
     *             Throws servlet exception if encounters some server errors.
     * @throws IOException
     *             Throws IOException if encounter some io write/read errors.
     */
    @SuppressWarnings("deprecation")
    @Override
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        String emailAddress = request.getParameter("emailAddress");
        String password = request.getParameter("password");
        String realPath = request.getRealPath("/image");
        Map<String, List<String>> albumPhotos = generatePhoto(emailAddress,
                password, realPath);
        request.setAttribute("albumPhotos", albumPhotos);
        request.getRequestDispatcher("/result.jsp").forward(request, response);
    }

    /**
     * This method is to get the album, and all the photo's name and thumbnail
     * format name, and the photo's description.
     *
     * @param emailAddress
     *            The email address which you used to authenticated.
     * @param password
     *            The password which you used to authenticated.
     * @param realPath
     *            The realPath you want to save the images.
     * @return Map<String,List<Sring>> which represents the album and all the
     *         photos in that album. It always have the following format.
     *         albumName: test.png i_test.png This is the image's description.
     * @throws IOException
     *             Throws IOException if encounter some io write/read errors.
     */
    public Map<String, List<String>> generatePhoto(String emailAddress,
            String password, String realPath) throws IOException {
        if (emailAddress != null && password != null) {
            try {
                PicasawebService picasaService = buildPicasaWebService(
                        "Picasa", emailAddress, password);
                List<AlbumEntry> albums = getAlbums(picasaService, emailAddress);
                Map<String, List<String>> albumPhotos = new Hashtable<String, List<String>>();
                for (AlbumEntry albumEntry : albums) {
                    List<PhotoEntry> photoEntrys = getPhotos(picasaService,
                            albumEntry);
                    if (photoEntrys.size() > 0) {
                        List<String> photos = new ArrayList<String>();
                        for (PhotoEntry photoEntry : photoEntrys) {
                            String thumbnailsName = writeImage(photoEntry
                                    .getMediaThumbnails().get(0).getUrl(),
                                    realPath, false);
                            String originalName = writeImage(photoEntry
                                    .getMediaContents().get(0).getUrl(),
                                    realPath, true);
                            photos.add(thumbnailsName);
                            photos.add(originalName);
                            photos.add(photoEntry.getDescription()
                                    .getPlainText());
                        }
                        albumPhotos.put(albumEntry.getName(), photos);
                    }
                }
                return albumPhotos;
            } catch (AuthenticationException e) {
                e.printStackTrace();
            } catch (ServiceException e) {
                e.printStackTrace();
            }
        }
        return new Hashtable<String, List<String>>();
    }

    /**
     * This is method is to build a PicasawebService object using the
     * emailAddress and password, and the appName.
     *
     * @param appName
     *            The appname you want to set, in this program we set it
     *            "picasa"
     * @param emailAddress
     *            The email address of you used to authenticated.
     * @param password
     *            The password you used to authenticated.
     * @return The PicasawebService object.
     * @throws AuthenticationException
     *             If there exist some authentication exception occur.
     */
    public PicasawebService buildPicasaWebService(String appName,
            String emailAddress, String password)
            throws AuthenticationException {
        PicasawebService picasaService = new PicasawebService(appName);
        picasaService.setUserCredentials(emailAddress, password);
        return picasaService;
    }


    /**
     * This method is to extract a user's album.
     *
     * @param picasaService
     *            The picasawebService object, we use this object to get the
     *            user's feed.
     * @param username
     *            The user name which we want to get the all the album.
     * @return A list of AlbumEntrys.
     * @throws IOException
     *             There is some write/read exception occured.
     * @throws ServiceException
     *             This is some service exception occur, for example, the wrong
     *             URL
     */
    @SuppressWarnings("unchecked")
    public List<AlbumEntry> getAlbums(PicasawebService picasaService,
            String username) throws IOException, ServiceException {

        String albumUrl = API_PREFIX + username;
        UserFeed userFeed = picasaService.getFeed(new URL(albumUrl),
                UserFeed.class);

        List<GphotoEntry> entries = userFeed.getEntries();
        List<AlbumEntry> albums = new ArrayList<AlbumEntry>();
        for (GphotoEntry entry : entries) {
            GphotoEntry adapted = entry.getAdaptedEntry();
            if (adapted instanceof AlbumEntry) {
                albums.add((AlbumEntry) adapted);
            }
        }
        return albums;
    }

    /**
     * This method is to extract all the photos from a particular album.
     *
     * @param picasaService
     *            The picasawebService object, we use this object to get the
     *            user's feed.
     * @param album
     *            The AlbumEntry object which you want to get all the photos
     *            from it.
     * @return A list of PhotoEntry object.
     * @throws IOException
     *             There is some write/read exception occured.
     * @throws ServiceException
     *             This is some service exception occur, for example, the wrong
     *             URL
     */
    @SuppressWarnings("unchecked")
    public List<PhotoEntry> getPhotos(PicasawebService picasaService,
            AlbumEntry album) throws IOException, ServiceException {

        String feedHref = getLinkByRel(album.getLinks(), Link.Rel.FEED);
        AlbumFeed albumFeed = picasaService.getFeed(new URL(feedHref),
                AlbumFeed.class);

        List<GphotoEntry> entries = albumFeed.getEntries();
        List<PhotoEntry> photos = new ArrayList<PhotoEntry>();
        for (GphotoEntry entry : entries) {
            GphotoEntry adapted = entry.getAdaptedEntry();
            if (adapted instanceof PhotoEntry) {
                photos.add((PhotoEntry) adapted);
            }
        }
        return photos;
    }


    /**
     * This method is a helper method, is to get the href from with a link's
     * name from the corresponding links collection.
     *
     * @param links
     *            The Link collection you want to elect from.
     * @param relValue
     *            The corresponding value.
     * @return The real link's href value.
     */
    public String getLinkByRel(List<Link> links, String relValue) {
        for (Link link : links) {
            if (relValue.equals(link.getRel())) {
                return link.getHref();
            }
        }
        throw new IllegalArgumentException("Missing " + relValue + " link.");
    }


    /**
     * This method is to write the urlAddress's image to the server's "/image"
     * folder, and if it is the thumbnail, we just directly add a "i_" prefix to
     * distinguish,
     *
     * @param urlAddress
     *            The image URL address, it is a String object.
     * @param realPath
     *            The real path of "/image" folder, in that path you want to
     *            save this image.
     * @param isThumbnail
     *            Whether the image is thumbnail.
     * @return The filename of the image, if it is thumbnail manner.
     */
    public String writeImage(String urlAddress, String realPath,
            boolean isThumbnail) {
        try {
            URL url = new URL(urlAddress);
            BufferedInputStream bis = new BufferedInputStream(url.openStream());
            String fileName = getFileName(urlAddress, isThumbnail);
            byte[] bytes = new byte[1024];
            OutputStream bos = new FileOutputStream(new File(realPath + "\\"
                    + fileName));
            int len;
            while ((len = bis.read(bytes)) > 0) {
                bos.write(bytes, 0, len);
            }
            bis.close();
            bos.flush();
            bos.close();
            return fileName;
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return "";
    }

    /**
     * This method is to get the file name from the URL address, and if it is
     * thumbnail, add a "i_" prefix to distinguish.
     *
     * @param urlAddress
     *            The URL address that contains the real image address.
     * @param isThumbnail
     *            Whether this image is thumbnail
     * @return The formated filename of this image represented by the URL
     *         address.
     */
    public String getFileName(String urlAddress, boolean isThumbnail) {
        int lastURLSeparater = urlAddress.lastIndexOf("/");
        if (isThumbnail) {
            return urlAddress.substring(lastURLSeparater + 1);
        } else {
            return "i_" + urlAddress.substring(lastURLSeparater + 1);
        }
    }
}

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<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Input the emailAddress and password</title>
</head>
<body>
<form action="servlet/picasaServlet" method="post">
    <label>Input emailAddress:</label>
    <input type="text" name="emailAddress" />
    <label>Input password:</label>
    <input type="password"" name="password" />
    <input type="submit" value="submit">
</form>
</body>
</html>

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<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Input the emailAddress and password</title>
</head>
<body>

    <%
        Map<String,List<String>> albumPhotos =
            (Map<String,List<String>>)request.getAttribute("albumPhotos");
        for(Iterator<String> it = albumPhotos.keySet().iterator(); it.hasNext();){
            String albumName = it.next();
            List<String> photos = albumPhotos.get(albumName);
    %>
        albumName:<%=albumName%><br>
        <%for(int i = 0; i < photos.size(); i+=3){%>
        Thumbnails: <img alt="" src="<%=request.getContextPath()%>/image/<%=photos.get(i)%>"><br>
        Original: <img alt="" src="<%=request.getContextPath()%>/image/<%=photos.get(i+1)%>"><br>
        Description: <%=photos.get(i+2)%>

    <%
            }
        }
    %>

</body>
</html>

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