axum/src/extract/query.rs

use super::{rejection::*, FromRequest, RequestParts};
use async_trait::async_trait;
use serde::de::DeserializeOwned;
use std::ops::Deref;

/// Extractor that deserializes query strings into some type.
///
/// `T` is expected to implement [`serde::Deserialize`].
///
/// # Example
///
/// ```rust,no_run
/// use axum::prelude::*;
/// use serde::Deserialize;
///
/// #[derive(Deserialize)]
/// struct Pagination {
///     page: usize,
///     per_page: usize,
/// }
///
/// // This will parse query strings like `?page=2&per_page=30` into `Pagination`
/// // structs.
/// async fn list_things(pagination: extract::Query<Pagination>) {
///     let pagination: Pagination = pagination.0;
///
///     // ...
/// }
///
/// let app = route("/list_things", get(list_things));
/// # async {
/// # hyper::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
/// # };
/// ```
///
/// If the query string cannot be parsed it will reject the request with a `400
/// Bad Request` response.
#[derive(Debug, Clone, Copy, Default)]
pub struct Query<T>(pub T);

#[async_trait]
impl<T, B> FromRequest<B> for Query<T>
where
    T: DeserializeOwned,
    B: Send,
{
    type Rejection = QueryRejection;

    async fn from_request(req: &mut RequestParts<B>) -> Result<Self, Self::Rejection> {
        let query = req
            .uri()
            .ok_or(UriAlreadyExtracted)?
            .query()
            .ok_or(QueryStringMissing)?;
        let value = serde_urlencoded::from_str(query)
            .map_err(FailedToDeserializeQueryString::new::<T, _>)?;
        Ok(Query(value))
    }
}

impl<T> Deref for Query<T> {
    type Target = T;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}