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.
