Hi there,
I'm new to Google App Engine, and was wondering what I'm doing wrong.
In my application, users upload (potentially large) images into the
Blobstore. I also need to create a thumbnail image that is 300px wide
(and high enough to maintain aspect ratio). Although
ImagesServiceFactory.makeImageFromBlob(blobKey) returns an Image
that's not null, when I try to access width and height properties of
the returned image I get an UnsupportedOperationException "No image
data is available.".
Here is the simplest code I can think of to reproduce (this is based
on blobstore example; to make it work setup that example, then add a
web.xml entry for this servlet and then change the "upload" servlet
mapping to point to it):
import java.io.IOException;
import java.util.Map;
import java.util.logging.Logger;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.google.appengine.api.blobstore.BlobKey;
import com.google.appengine.api.blobstore.BlobstoreService;
import com.google.appengine.api.blobstore.BlobstoreServiceFactory;
import com.google.appengine.api.images.Image;
import com.google.appengine.api.images.ImagesServiceFactory;
public class ImageBlobBug extends HttpServlet {
private static final long serialVersionUID = 1L;
private BlobstoreService blobstoreService =
BlobstoreServiceFactory.getBlobstoreService();
private static final Logger log =
Logger.getLogger(ImageBlobBug.class.getName());
public void doPost(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
Map<String, BlobKey> blobs =
blobstoreService.getUploadedBlobs(req);
BlobKey blobKey = blobs.get("myFile");
Image image = ImagesServiceFactory.makeImageFromBlob(blobKey);
res.sendRedirect("#"+ (image == null ? "Image could not be made
from
blob":"Image successfully retrieved with height: " +
image.getHeight()));
}
}
Here is the stacktrace:
java.lang.UnsupportedOperationException: No image data is available.
at
com.google.appengine.api.images.ImageImpl.updateDimensions(ImageImpl.java:
130)
at com.google.appengine.api.images.ImageImpl.getHeight(ImageImpl.java:
63)
at ImageBlobBug.doPost(ImageBlobBug.java:27)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
487)
at
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:
362)
at
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:
216)
at
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:
181)
at
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:
712)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
405)
at
com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:
70)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:268)
at org.mortbay.jetty.servlet.Dispatcher.forward(Dispatcher.java:126)
at
com.google.appengine.api.blobstore.dev.UploadBlobServlet.handleUpload(UploadBlobServlet.java:
368)
at com.google.appengine.api.blobstore.dev.UploadBlobServlet.access
$000(UploadBlobServlet.java:72)
at com.google.appengine.api.blobstore.dev.UploadBlobServlet
$1.run(UploadBlobServlet.java:100)
at java.security.AccessController.doPrivileged(Native Method)
at
com.google.appengine.api.blobstore.dev.UploadBlobServlet.doPost(UploadBlobServlet.java:
98)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:713)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:806)
at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:
487)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1093)
at
com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:
51)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1084)
at
com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:
43)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1084)
at
com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:
121)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1084)
at
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:
360)
at
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:
216)
at
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:
181)
at
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:
712)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
405)
at
com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:
70)
at
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
139)
at com.google.appengine.tools.development.JettyContainerService
$ApiProxyHandler.handle(JettyContainerService.java:352)
at
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
139)
at org.mortbay.jetty.Server.handle(Server.java:313)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:
506)
at org.mortbay.jetty.HttpConnection
$RequestHandler.content(HttpConnection.java:844)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:644)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:211)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:381)
at
org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:
396)
at org.mortbay.thread.BoundedThreadPool
$PoolThread.run(BoundedThreadPool.java:442)
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