Thanks for shedding some light on the issue. I will give it a try. Carl On 21 jan 2011, at 17:19, Didier Durand <durand.did...@gmail.com> wrote:
> Hi, > > You have 2 distinguish between 2 types of blobs: > > - Blob as an object managed by the Blobstore: up 2 to gigabytes. See > http://code.google.com/appengine/docs/java/blobstore/overview.html > > - Blob as a Java type used by app engine: up to 1 megabyte. See > http://code.google.com/appengine/docs/java/datastore/entities.html#Properties_and_Value_Types > > If you generate your data on GAE and want to store them, you have to > generate and store them as a linkrd list of Blobs (the java type) that > you manage by yourself. So, you can then have N x 1 Mb with no limit > on N. > > You will face a problem though: an interactive request cannot last > more than 30s as of now, so if your file is huge, you may not be able > to download all of its blobs in 30s. > > Then, you would need to write to the blobstore, which is not possible > directly: you have to use the trick described here: > http://groups.google.com/group/google-appengine-java/browse_thread/thread/2bea1295a3f542de/854ea95dcd986dab. > And, once again you should not do this in an interactive request by in > a task that you queued because then the processing limit is raised to > 10 min. > > So, to summarize, you should try to: generate your file into blobs if > needed in a 1st task and then in a second task, concatenate this list > of small 1 mb blobs to a large blob object into the blobstore which > will then be downlaodable as any other after you fetch the url imposed > by the blobstore. > > To be honest, I never did this mechanism in full length at once: i use > all the parts in various occasion. So, I guess that you can put them > one after the other to reach you goal. > > Of course, something more straight would be nice. I look forward to > seeing a much simpler proposal than this one. > > regards > > didier > > On Jan 21, 4:32 pm, c...@rahmstrom.com wrote: >> I'm writing an application in GWT/GAE that needs to be able to import/export >> data from/to custom files. Import is no problem but how do I go about >> generating a custom file for download? >> >> I understand that GAE does not support File and instead uses Blobs and that >> it is possible to download a file generated from that Blob. However, I can >> not find a way to generate Blobs other than to upload static files. Is this >> correct? I would like to be able to write to a Blob via a stream. Or is >> there an other way? >> >> Carl > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine for Java" group. > To post to this group, send email to google-appengine-java@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine-java+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/google-appengine-java?hl=en. > -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-java@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.
