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1 Minimal

1.1 Devs, start your servers

To start sending our "Hello"s to the world with actix, we'll be using HttpServer, and App, but what are these things?

App is an application builder used to configure things like: routes, data, and middleware. Instances of App are created and ran by the HttpServer, which does the actual heavy lifting (it starts the threads, binds an address, listens for requests, and more).

You don't have to get intimately familiar with HttpServer, as most of the things are set in App.

We'll be using HttpServer's new, bind, and run. This is everything we'll need to start and run the web server.

You may have noticed that HttpServer::new expects some factory: F, and we're passing it a closure (a move closure to be precise), what is going on here?

To avoid digging too deep here, this F generic parameter represents a function trait (Fn), so we feed it a closure that fulfills the HttpServer::new requirements.

1.2 Services and routes (and macros)

The minimal project could've been written with the route macro instead of the get macro:

// actix-web::route macro example
#[route("/", method="GET")]
async fn index() -> HttpResponse {
    let response = HttpResponse::Ok()
        .content_type("text/html; charset=UTF-8")
        .body(WELCOME_MSG);
    response
}

Using the route macro (and the App::route function) allows more than one HTTP method to be handled by the same function, while the get (and friends) macro is specific to one HTTP method:

// actix-web::route macro example, multiple methods
#[route("/", method="GET", method="POST", method="PUT")]
async fn index() -> HttpResponse {
    let response = HttpResponse::Ok()
        .content_type("text/html; charset=UTF-8")
        .body(WELCOME_MSG);
    response
}

I prefer to have separate functions for each method, thus the examples will be using the macro that matches the method (get, post, and so on), even though we could do the same thing with route.

The examples will also use App::service, instead of the very similar App::route, which is just a simplified version of App::service.

1.3 That's it

This project doesn't have many interesting things going on. To sum everything it does:

  1. Create a route handler with the get macro;
  2. Configure our App with only one service, index;
  3. Build and run the HttpServer;

Instead of hard-coding the response string in the HttpResponseBuilder::body (notice that we're using a builder here to create the actual HttpResponse) function, we include a file with the handy rust macro include_str!.