axum/extension.rs
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use crate::{extract::rejection::*, response::IntoResponseParts};
use async_trait::async_trait;
use axum_core::{
extract::FromRequestParts,
response::{IntoResponse, Response, ResponseParts},
};
use http::{request::Parts, Request};
use std::{
convert::Infallible,
task::{Context, Poll},
};
use tower_service::Service;
/// Extractor and response for extensions.
///
/// # As extractor
///
/// This is commonly used to share state across handlers.
///
/// ```rust,no_run
/// use axum::{
/// Router,
/// Extension,
/// routing::get,
/// };
/// use std::sync::Arc;
///
/// // Some shared state used throughout our application
/// struct State {
/// // ...
/// }
///
/// async fn handler(state: Extension<Arc<State>>) {
/// // ...
/// }
///
/// let state = Arc::new(State { /* ... */ });
///
/// let app = Router::new().route("/", get(handler))
/// // Add middleware that inserts the state into all incoming request's
/// // extensions.
/// .layer(Extension(state));
/// # let _: Router = app;
/// ```
///
/// If the extension is missing it will reject the request with a `500 Internal
/// Server Error` response.
///
/// # As response
///
/// Response extensions can be used to share state with middleware.
///
/// ```rust
/// use axum::{
/// Extension,
/// response::IntoResponse,
/// };
///
/// async fn handler() -> (Extension<Foo>, &'static str) {
/// (
/// Extension(Foo("foo")),
/// "Hello, World!"
/// )
/// }
///
/// #[derive(Clone)]
/// struct Foo(&'static str);
/// ```
#[derive(Debug, Clone, Copy, Default)]
#[must_use]
pub struct Extension<T>(pub T);
#[async_trait]
impl<T, S> FromRequestParts<S> for Extension<T>
where
T: Clone + Send + Sync + 'static,
S: Send + Sync,
{
type Rejection = ExtensionRejection;
async fn from_request_parts(req: &mut Parts, _state: &S) -> Result<Self, Self::Rejection> {
let value = req
.extensions
.get::<T>()
.ok_or_else(|| {
MissingExtension::from_err(format!(
"Extension of type `{}` was not found. Perhaps you forgot to add it? See `axum::Extension`.",
std::any::type_name::<T>()
))
}).cloned()?;
Ok(Extension(value))
}
}
axum_core::__impl_deref!(Extension);
impl<T> IntoResponseParts for Extension<T>
where
T: Clone + Send + Sync + 'static,
{
type Error = Infallible;
fn into_response_parts(self, mut res: ResponseParts) -> Result<ResponseParts, Self::Error> {
res.extensions_mut().insert(self.0);
Ok(res)
}
}
impl<T> IntoResponse for Extension<T>
where
T: Clone + Send + Sync + 'static,
{
fn into_response(self) -> Response {
let mut res = ().into_response();
res.extensions_mut().insert(self.0);
res
}
}
impl<S, T> tower_layer::Layer<S> for Extension<T>
where
T: Clone + Send + Sync + 'static,
{
type Service = AddExtension<S, T>;
fn layer(&self, inner: S) -> Self::Service {
AddExtension {
inner,
value: self.0.clone(),
}
}
}
/// Middleware for adding some shareable value to [request extensions].
///
/// See [Sharing state with handlers](index.html#sharing-state-with-handlers)
/// for more details.
///
/// [request extensions]: https://docs.rs/http/latest/http/struct.Extensions.html
#[derive(Clone, Copy, Debug)]
pub struct AddExtension<S, T> {
pub(crate) inner: S,
pub(crate) value: T,
}
impl<ResBody, S, T> Service<Request<ResBody>> for AddExtension<S, T>
where
S: Service<Request<ResBody>>,
T: Clone + Send + Sync + 'static,
{
type Response = S::Response;
type Error = S::Error;
type Future = S::Future;
#[inline]
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, mut req: Request<ResBody>) -> Self::Future {
req.extensions_mut().insert(self.value.clone());
self.inner.call(req)
}
}