I ran into a problem yesterday. I’d sent a HTTP POST request to a collection of resources on our RESTful web service. Our server responded with an HTTP 201: Created status code and the URI of the new resource in the Location header.
And then… nothing happened.
This was not what I was expecting. I expected my web browser to follow up with a GET request to the URI I’d provided. But Firefox 3 wasn’t biting. A problem with Firefox? I checked in IE8 and Google Chrome and got the same behavior.
Had I misread the HTTP spec? Did I misunderstand the REST pattern? I grabbed for my worn copy of RESTful Web Services. Nope. HTTP 201 seemed to be the right status for this situation.
Had I blundered into some common error? I checked Stefan Tilkov’s useful list of REST Antipatterns. But I couldn’t find anything that quite matched my situation.
I started Googling, but couldn’t find much apart from this question about HTTP Post on Stack Overflow. There were some cryptic responses (to which I’ve added my own answer now).
Eventually, I discovered what I needed to know from Ben Ramsey’s article on HTTP redirection. It’s part of his series discussing RFC 2616, which describes the HTTP/1.1 protocol.
The answer is that while web service clients will often “take the hint” provided by a HTTP 201: Created response, web browsers won’t. If you actually want a web browser to go somewhere else, you need to send a status code in the 3xx series. In this situation, the status code you want is HTTP 303: See Other.
Once I changed the status code returned by the server, all the web browsers followed up the response with a GET to the new URI.
I just answered a WCF question on StackOverflow, and decided it was worth cross-posting here as well.
The question was: What is the best / most flexible way to have WCF output XHTML?
Here’s how we do it at Infovark. While I’m not sure that our approach is the best way, it does the job.
Our approach is to use the DataContractSerilizer to generate XML, then apply a Complied XSLT transform and return the result stream, which should now contain XHTML. Here’s a simplified version of our code:
It works for us, but if you’ve got other, better ideas, please let me know!
I’m on record as being skeptical of the semantic web. Or rather, I’m skeptical of much of the marketing hype around the semantic web. That’s not to say that semantic technologies won’t be useful.
I still believe that both Resource Description Framework (RDF) and the Web Ontology Language (OWL) are too complicated to gain widespread adoption. But maybe we don’t need their academic rigor. Microformats offer a way to get some of the benefits of the semantic web using plain ol’ HTML.
What are microformats? How do they work? Emily Lewis wrote a great series of blog posts introducing microformats. You can also go direct to the source, the microformats homepage, at microformats.org.
Here’s an example of our company address in hCard format.
The address above is marked up in such a way that (some) web browsers can identify it as a street address. But it’s nothing more than ordinary HTML. Here’s what the code looks like:
It’s simple enough that it just might deliver where RDF and OWL fail, becoming part of every web developer’s toolkit.
You can experiment by creating your own hCards using the hCard creator.
And if you’re using Mozilla Firefox, you can download the Operator add-in to see — and use — microformatted data embedded in ordinary web pages.
Hat tip: Ajaxian for Getting Semantic with Mircoformats
I’m staring at a gorgeous visual right now. It’s an image of how the Infovark UI might look. I can imagine myself clicking on that tab, and navigating off to a world of beautifuly laid out, useful information…
I really want to see this go into production. I really do…
But it won’t. Our designer used Photoshop.
There’s nothing wrong with Photoshop, of course. Nor Gimp, nor Paint.Net, nor any other image editing tool you could mention. And there’s nothing wrong with our designer, either. She really knows her stuff. But I can’t help but feel that perhaps you shouldn’t let your designer touch an image editing tool when she’s working on a web design.
When you open an image editing tool, you’re presented with a blank canvas. And the first instinct of any artist or designer is to fill that canvas.
Web pages aren’t canvas. On canvas, or on paper, it’s just as easy to paint one corner as another. This isn’t true of the web. With a web page, one corner is much easier to reach than all the others. In languages written left to right, it’s the upper left hand corner.
Not all sides of the image are equally easy to reach, either. The top and left edges of your canvas are much, much easier to paint than the right or bottom edge.
It’s as if the upper left corner has its own gravity, and draws all other page elements toward it. Like a black hole, it warps your grid.
It is many times harder to place elements in the bottom right corner of a page than the upper left. You’re fighting the pull of gravity the whole way. You’ll have to build on top of block elements like DIV to get there. And beware of the CSS float property. As its name suggests, it isn’t supported by anything. It can wreak havoc on your layout, setting off a cascade of unwanted effects.
The web also suffers from typographic poverty. In an image editing tool, your designer will have access to hundreds — perhaps thousands — of fonts. They can be used to create images freely. But all but a handful of these fonts can be used on the web. Most designers know what fonts are actually available for use. You can cheat in certain cases, and use images instead of text for certain headers and buttons, but many of the effects you’d like to achieve with typography are simply not possible today.
Your web canvas won’t take all kinds of paint, either, unlike an ordinary image file. Not all browsers support transparency in images, for example. Placing gradients and shadows can be tricky.
But the biggest challenge can be the dynamic nature of a web page. Looking at a design, it can be hard to imagine the effect a blinking, spinning animated widget will have on your audience. It’s also hard to visualize what rollovers or pop-ups might do to the overall feel of the page.
Unlike paper or canvas, a web page can be stretched and scrolled. What does that do to the positioning of its elements? What happens when a user adjusts the font size in the browser, but embedded gifs and jpgs remain the same size?
But the biggest drawback to having your designer work in Photoshop is that to the layman, the web site looks almost finished. They’re pretty, these Photoshop Sirens, and they sing! They will draw you in…
Only the lonely code monkey hacking away at HTML, CSS and JavaScript knows that a screenshot is as far away from a working web page as a screenplay is from a feature film.