Comments on: JSON-head, it is not about size – it is about usefulness

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By: SimonWillison

SimonWillison — Tue, 29 Jul 2008 18:03:52 +0000

ragjunk: I consider that a bug, but unfortunately the App Engine urlfetch API automatically follows HTTP redirects: http://code.google.com/appengine/docs/urlfetch/overview.html

There are a couple of relevant tickets in their issue tracker; I just posted a comment on this one: http://code.google.com/p/googleappengine/issues/detail?id=363

By: ragjunk

ragjunk — Tue, 29 Jul 2008 17:41:54 +0000

Actually, it didn’t help. Running:

http://json-head.appspot.com/?url=http://docs.google.com

produced a status_code of 200. If you run, http://docs.google.com directly, you will be redirected to:

https://www.google.com/accounts/ServiceLogin?service=writely&passive=true&nui=1&continue=http%3A%2F%2Fdocs.google.com%2F&followup=http%3A%2F%2Fdocs.google.com%2F<mpl=homepage&rm=false

I assumed json-head would return 302, which is what I see in Fiddler2.

By: tapwater

tapwater — Tue, 29 Jul 2008 17:40:16 +0000

V1: This could be useful when working with CouchDB.

By: SimonWillison

SimonWillison — Tue, 29 Jul 2008 17:39:36 +0000

Here’s one example (the reason I built it in fact) – I’m creating an interface for constructing podcast RSS feeds, which needs to include the length of each mp3 file in bytes in the enclosure element. The MP3s are online already. When the user pastes the URL to the MP3 in to the admin application, I can unobtrusively use json-head to find the Content-Length of that file and populate the “size” field in the interface for them. Because it uses JSON-P I can call the script from anywhere, and because it’s on App Engine I don’t have to worry about hosting a potentially expensive operation on my own server.

By: ragjunk

ragjunk — Tue, 29 Jul 2008 17:30:11 +0000

I have a use case where an URL is requested in an iframe. If the HTTP response contains a 301 or 302, IE does a redirect, which replaces the “entire” page, not just the iframe content. There is no way to overcome this issue, at least to my knowledge. With this library, I think, I can examine the status_code and set the iframe’ src to the original URL if the status code is 200 and to the redirected URL, if it is 301 or 302.

By: V1

V1 — Tue, 29 Jul 2008 17:29:12 +0000

U got analytic and 404 error logs for that..

By: Chris Heilmann

Chris Heilmann — Tue, 29 Jul 2008 17:25:35 +0000

I think I did…

By: V1

V1 — Tue, 29 Jul 2008 17:08:07 +0000

name one good practice where this comes in use…
Rather useless if u ask me…