Serve image from blob store

[Ahmed Shoeib]

hi all,
i want to get image from blobstore using this code

// Serve image from blob store
BlobKey blobKey = new BlobKey(req.getParameter("apikey"));
blobstoreService.serve(blobKey, resp);

and facing this problem

HTTP ERROR 500

Problem accessing /api/news/serve. Reason:

WRITER

Caused by:

java.lang.IllegalStateException: WRITER
at org.mortbay.jetty.Response.getOutputStream(Response.java:594)
at
javax.servlet.ServletResponseWrapper.getOutputStream(ServletResponseWrapper.java:
105)
at
com.google.appengine.api.blobstore.dev.ServeBlobFilter.serveBlob(ServeBlobFilter.java:
169)
at
com.google.appengine.api.blobstore.dev.ServeBlobFilter.doFilter(ServeBlobFilter.java:
62)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1157)
at
com.google.apphosting.utils.servlet.TransactionCleanupFilter.doFilter(TransactionCleanupFilter.java:
43)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1157)
at
com.google.appengine.tools.development.StaticFileFilter.doFilter(StaticFileFilter.java:
122)
at org.mortbay.jetty.servlet.ServletHandler
$CachedChain.doFilter(ServletHandler.java:1157)
at
org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:
388)
at
org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:
216)
at
org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:
182)
at
org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:
765)
at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:
418)
at
com.google.apphosting.utils.jetty.DevAppEngineWebAppContext.handle(DevAppEngineWebAppContext.java:
70)
at
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
152)
at com.google.appengine.tools.development.JettyContainerService
$ApiProxyHandler.handle(JettyContainerService.java:349)
at
org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:
152)
at org.mortbay.jetty.Server.handle(Server.java:326)
at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:
542)
at org.mortbay.jetty.HttpConnection
$RequestHandler.headerComplete(HttpConnection.java:923)
at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:547)
at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
at
org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:
409)
at org.mortbay.thread.QueuedThreadPool
$PoolThread.run(QueuedThreadPool.java:582)

[Matthew Hill]

Try the Google App Engine group:

https://groups.google.com/forum/#!forum/google-appengine

or the GAE Java group.

[Ahmed Shoeib]

ok thanks

[Subhrajyoti Moitra]

Hello Ahmed,

http://anansu.blogspot.com/2010/12/upload-serve-and-search-images-using.html

Here's a small write-up and sources to a GWT+GAE+Eclipse project, using BlobStore to store and serve images. This is meant for learning purpose only.
Also this is not the only way you can do it. There are better ways most probably.

Hope this helps.


Thanks,
Subhro.

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[zixzigma]

I believe you are using an API that is restricted on GAE.
support for File/IO operations are very limited on GAE,
and when using third party libraries such as Apache Commons,
not all of their features is supported.
check GAE WhiteList to see what is supported.

Often you have to look for alternatives.
What might be very easy in JRE, requires some tricks to get it to work
on GAE.

[Subhrajyoti Moitra]

yes, u are right. Have to be careful about that on GAE.

For the common-libs, i am only using the file upload apis, which seems to be allowed on GAE.
Also some utils from commons-lang lib, which are compatible.

Thanks,
Subhro.

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