03-hello-world.md

Hello World

Add project name to workspace.

[workspace]

members = [
    "hello-world", # <--
]

Create the project.

cargo new hello-world

Dependencies

Example Cargo.toml:

[package]
name = "hello-world"
version = "0.1.0"
edition = "2021"

[dependencies]
axum = "0.5"
tokio = { version = "1", features = ["full"] }

These dependencies are required to create a bare minimum axum application.

tokio is a really popular library to work with async code. rust doesn't come with a default async runtime, this leaves the choice to users. axum only supports tokio runtime. But don't worry tokio has everything you can possibly want from an async library.

Code

use axum::{routing::get, Router};
use std::net::SocketAddr;

#[tokio::main]
async fn main() {
    // Route all requests on "/" endpoint to anonymous handler.
    //
    // A handler is an async function which returns something that implements
    // `axum::response::IntoResponse`.

    // A closure or a function can be used as handler.

    let app = Router::new().route("/", get(handler));
    //        Router::new().route("/", get(|| async { "Hello, world!" }));

    // Address that server will bind to.
    let addr = SocketAddr::from(([127, 0, 0, 1], 3000));

    // Use `hyper::server::Server` which is re-exported through `axum::Server` to serve the app.
    axum::Server::bind(&addr)
        // Hyper server takes a make service.
        .serve(app.into_make_service())
        .await
        .unwrap();
}

async fn handler() -> &'static str {
    "Hello, world!"
}

Run

Execute this command in workspace directory:

cargo run --bin hello-world

Enter http://localhost:3000 in browser.

Next

Create an application that responds with a random number from query parameters.