Using middleware applications in a Rackup file is very simple. Simply call the use method with the class name of a middleware application to run. For example, we'll use the ContentLength middleware application with our HelloWorld application, which will add a Content-Length header.
#\ -p 1337
use Rack::ContentLength
class HelloWorld
def call(env)
return [
200,
{'Content-Type' => 'text/html'},
["Hello world!"]
]
end
end
run HelloWorld.new
If you were to examine the HTTP response headers with something like Firebug (a great web development extension for Firefox), you would see that the Rack::ContentLength middleware application added a Content-Length header.
