One of the more interesting pieces of ASP.NET is the concept
of HttpHandlers. Sadly, this article does not delve much into what handlers are
or for what they are used. Instead, this article just gives a quick introduction
for you to be able to write your own HttpHandler. The text following explains
how to create a simple HttpHandler, and a few of the design decisions you will
have to make when creating your own. You can download
the sample project for this article here or at the bottom of the article.
There are plenty of ways in which one can benefit from the
use of HttpHandlers. They are very versatile. They can be applied to a lot of
different tasks. Keep in mind there are also HttpModules which are also extremely
useful tools, but they are a bit different from HttpHandlers. I will not be
delving into that topic in this article. Please read elsewhere to learn more
about the differences between HttpHandlers and HttpModules.
I know plenty of people who have configured IIS to send all
requests for gifs, pngs, jpgs, etc. to ASP.NET HttpHandlers so that site owners
can clamp down on hotlinking, leeching, or whatever you want to call it. It is where
someone else links to your sites content. It uses your bandwidth and you do not
even get the traffic, and usually it does not mention where the content came
from.
Other people will configure IIS to handle zip files so that
an HttpHandler can step in and execute code every time someone wants to
download a file from a site. This is much easier than some of the scripted
downloads, and certainly gives great server-side control over the download - counting
the number of downloads and storing in a database or whatever you want to do.
One other use of HttpHandlers, which I plan to write about
soon, is to use them to watermark your images. If you have configured an
HttpHandler to prevent people from leeching your images you might also use a
handler to watermark your images with a copyright. This makes it less likely
that people will simply save your images and display them on their own pages.
Plenty of people and companies are quite concerned about this. Keep in mind
that if you publish something on the internet it can never be completely safe,
but you can at least discourage people.
