2021-06-19 12:34:42 +02:00
|
|
|
//! Example showing how to convert errors into responses and how one might do
|
|
|
|
|
//! dependency injection using trait objects.
|
2021-08-02 23:09:09 +02:00
|
|
|
//!
|
|
|
|
|
//! Run with
|
|
|
|
|
//!
|
|
|
|
|
//! ```not_rust
|
|
|
|
|
//! cargo run --example error_handling_and_dependency_injection
|
|
|
|
|
//! ```
|
2021-06-19 12:34:42 +02:00
|
|
|
|
|
|
|
|
#![allow(dead_code)]
|
|
|
|
|
|
2021-07-09 21:36:14 +02:00
|
|
|
use axum::{
|
2021-06-19 12:34:42 +02:00
|
|
|
async_trait,
|
|
|
|
|
extract::{Extension, Json, UrlParams},
|
|
|
|
|
prelude::*,
|
|
|
|
|
response::IntoResponse,
|
|
|
|
|
AddExtensionLayer,
|
|
|
|
|
};
|
|
|
|
|
use http::StatusCode;
|
|
|
|
|
use serde::{Deserialize, Serialize};
|
|
|
|
|
use serde_json::json;
|
|
|
|
|
use std::{net::SocketAddr, sync::Arc};
|
|
|
|
|
use uuid::Uuid;
|
|
|
|
|
|
|
|
|
|
#[tokio::main]
|
|
|
|
|
async fn main() {
|
2021-08-01 22:01:33 +02:00
|
|
|
tracing_subscriber::fmt::init();
|
|
|
|
|
|
2021-06-19 12:34:42 +02:00
|
|
|
// Inject a `UserRepo` into our handlers via a trait object. This could be
|
|
|
|
|
// the live implementation or just a mock for testing.
|
|
|
|
|
let user_repo = Arc::new(ExampleUserRepo) as DynUserRepo;
|
|
|
|
|
|
|
|
|
|
// Build our application with some routes
|
|
|
|
|
let app = route("/users/:id", get(users_show))
|
|
|
|
|
.route("/users", post(users_create))
|
|
|
|
|
// Add our `user_repo` to all request's extensions so handlers can access
|
|
|
|
|
// it.
|
2021-06-19 14:06:49 +02:00
|
|
|
.layer(AddExtensionLayer::new(user_repo));
|
2021-06-19 12:34:42 +02:00
|
|
|
|
|
|
|
|
// Run our application
|
|
|
|
|
let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
|
|
|
|
|
tracing::debug!("listening on {}", addr);
|
2021-06-19 12:50:33 +02:00
|
|
|
hyper::Server::bind(&addr)
|
|
|
|
|
.serve(app.into_make_service())
|
|
|
|
|
.await
|
|
|
|
|
.unwrap();
|
2021-06-19 12:34:42 +02:00
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// Handler for `GET /users/:id`.
|
|
|
|
|
///
|
|
|
|
|
/// Extracts the user repo from request extensions and calls it. `UserRepoError`s
|
|
|
|
|
/// are automatically converted into `AppError` which implements `IntoResponse`
|
|
|
|
|
/// so it can be returned from handlers directly.
|
|
|
|
|
async fn users_show(
|
|
|
|
|
UrlParams((user_id,)): UrlParams<(Uuid,)>,
|
|
|
|
|
Extension(user_repo): Extension<DynUserRepo>,
|
|
|
|
|
) -> Result<response::Json<User>, AppError> {
|
|
|
|
|
let user = user_repo.find(user_id).await?;
|
|
|
|
|
|
|
|
|
|
Ok(user.into())
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// Handler for `POST /users`.
|
|
|
|
|
async fn users_create(
|
|
|
|
|
Json(params): Json<CreateUser>,
|
|
|
|
|
Extension(user_repo): Extension<DynUserRepo>,
|
|
|
|
|
) -> Result<response::Json<User>, AppError> {
|
|
|
|
|
let user = user_repo.create(params).await?;
|
|
|
|
|
|
|
|
|
|
Ok(user.into())
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// Our app's top level error type.
|
|
|
|
|
enum AppError {
|
|
|
|
|
/// Something went wrong when calling the user repo.
|
|
|
|
|
UserRepo(UserRepoError),
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// This makes it possible to use `?` to automatically convert a `UserRepoError`
|
|
|
|
|
/// into an `AppError`.
|
|
|
|
|
impl From<UserRepoError> for AppError {
|
|
|
|
|
fn from(inner: UserRepoError) -> Self {
|
|
|
|
|
AppError::UserRepo(inner)
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
impl IntoResponse for AppError {
|
|
|
|
|
fn into_response(self) -> http::Response<Body> {
|
|
|
|
|
let (status, error_json) = match self {
|
|
|
|
|
AppError::UserRepo(UserRepoError::NotFound) => {
|
|
|
|
|
(StatusCode::NOT_FOUND, json!("User not found"))
|
|
|
|
|
}
|
|
|
|
|
AppError::UserRepo(UserRepoError::InvalidUsername) => {
|
|
|
|
|
(StatusCode::UNPROCESSABLE_ENTITY, json!("Invalid username"))
|
|
|
|
|
}
|
|
|
|
|
};
|
|
|
|
|
|
|
|
|
|
let mut response = response::Json(json!({
|
|
|
|
|
"error": error_json,
|
|
|
|
|
}))
|
|
|
|
|
.into_response();
|
|
|
|
|
|
|
|
|
|
*response.status_mut() = status;
|
|
|
|
|
|
|
|
|
|
response
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// Example implementation of `UserRepo`.
|
|
|
|
|
struct ExampleUserRepo;
|
|
|
|
|
|
|
|
|
|
#[async_trait]
|
|
|
|
|
impl UserRepo for ExampleUserRepo {
|
|
|
|
|
async fn find(&self, _user_id: Uuid) -> Result<User, UserRepoError> {
|
|
|
|
|
unimplemented!()
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
async fn create(&self, _params: CreateUser) -> Result<User, UserRepoError> {
|
|
|
|
|
unimplemented!()
|
|
|
|
|
}
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// Type alias that makes it easier to extract `UserRepo` trait objects.
|
|
|
|
|
type DynUserRepo = Arc<dyn UserRepo + Send + Sync>;
|
|
|
|
|
|
|
|
|
|
/// A trait that defines things a user repo might support.
|
|
|
|
|
#[async_trait]
|
|
|
|
|
trait UserRepo {
|
|
|
|
|
/// Loop up a user by their id.
|
|
|
|
|
async fn find(&self, user_id: Uuid) -> Result<User, UserRepoError>;
|
|
|
|
|
|
|
|
|
|
/// Create a new user.
|
|
|
|
|
async fn create(&self, params: CreateUser) -> Result<User, UserRepoError>;
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
#[derive(Debug, Serialize)]
|
|
|
|
|
struct User {
|
|
|
|
|
id: Uuid,
|
|
|
|
|
username: String,
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
#[derive(Debug, Deserialize)]
|
|
|
|
|
struct CreateUser {
|
|
|
|
|
username: String,
|
|
|
|
|
}
|
|
|
|
|
|
|
|
|
|
/// Errors that can happen when using the user repo.
|
|
|
|
|
#[derive(Debug)]
|
|
|
|
|
enum UserRepoError {
|
|
|
|
|
NotFound,
|
|
|
|
|
InvalidUsername,
|
|
|
|
|
}
|
