Request Response

Request ⇄ Response chain is at the core of every web application — a browser makes a request that gets received by your web app, which in turn sends back a response based on what the request was.

As simple as this sounds on the surface, a lot of things have to happen in the correct order to successfully respond to a request call. There are many layers through which a request passes before returning a successful response to the client.

"Successful response" doesn't always mean returning with a response that the client wants/expects. It can also mean an error message with a status code — something very different from what the client was asking for.

Different frameworks implement these middle layers of converting request into a response differently. However, if you are coming from a dynamic language framework like Laravel, one main difference that you have to understand is that with those dynamic frameworks every conversion of request to response means, to simplify, starting a new copy of your app and passing the request through the app to make a response out of it and then shutting down the app.

A static language framework like Alpas works a bit differently!

Instead of starting a new app from scratch every time, you start your app once and then wait for a request. When it receives a request it spins up a new thread and processes the request until it gets converted to a response or the server dies because of an unhandled exception.

Request ⇄ Response Lifecycle

At a high level this is what happens when your Alpas web app receives a request:

Request Response Flow


Notice how Alpas wraps a request in an HttpCall object as soon as the application receives it. HttpCall is really the center character of the framework and the one you will interact with the most. It gets passed around pretty much everywhere and contains everything to handle a request — query parameters, headers, cookies, form request fields, session, etc. HttpCall is also a service container and so you could ask it for any core dependencies or any other dependencies that you have set the bindings for.

Not just the request, HttpCall is also where you would set a reply to an outgoing response, headers, cookies, etc.