Eric lippert - Amazon Web Services

• In the diagram we just saw, a user is sitting at the computer and types in a URL in the browser.
Notice that apart from the URL he also types in /suprotimagarwal which tells the server
‘something’.
• The browser sends this request over HTTP to (GET) the actual site. The discovery process of
www.twitter.com leverages the routing mechanism of the internet and it happens over port 80
using HTTP.
• The request is eventually sent to the Twitter server where it is processed by a web application
running a service on top of HTTP at port 80.
• This service then interprets ‘suprotimagarwal’ in the URL as a request to GET (as in the HTTP
request keyword) the profile of suprotimagarwal. Thus it makes appropriate backend calls to
retrieve the user profile data and sends it back to the requestor. In this case the user’s
browser renders the data that came in. Note, sometimes, the raw data may not be sent back,
instead the data is used to build the respective view and the complete view (in html) may be
returned, but in context of Web API, it’s not a view, only the data. Keep the term ‘Content Type
Negotiation’ in mind, we will circle back to it in the next section.
Overall the idea of Web API is to offer services that work seamlessly over HTTP as we saw
above. This is a great way to build public APIs for multiple client platforms.
Http and Content Types
Whenever we think of HTTP URLs and web browsers, we picture
HTML being received by the browser and then rendered.
However, there are instances when our browser renders an
image by itself, or plays music or shows a PDF document in
the browser itself. These are instances where data/content
other than html was sent over and the browser ‘understood’ the
‘Content Type’ and acted appropriately. For example, if we have
link to a PDF and the browser has a plugin for it, it can directly
display the PDF (in browser).
When you build Web API based services, you can return data
as JSON by default. However you can send out other types of
content as well. For example, if you are sending out Calendar
information, you can send it out as an iCal, when sending out
graphs data you can send out the rendered image and so on.
What type of data is acceptable to the client and what can the
server provide is a ‘negotiation’ that happens between the client
and the server before either a content type is agreed upon or a
406 (Not Acceptable) error is sent by the server implying, it
cannot provide data in any of the requested Content Types.
Media Formatters and Content
Types
As I mentioned briefly above, Web API services return data in
JSON or XML. This is because the data returned by the
Controller is converted into JSON or XML by a component
referred to as Media Formatter. Web API has two of these out
of the box, no points for guessing they are for JSON and XML
formats.
DNcmagazine www.dotnetcurry.com | 63