axum/
form.rs

1use crate::extract::Request;
2use crate::extract::{rejection::*, FromRequest, RawForm};
3use axum_core::response::{IntoResponse, Response};
4use axum_core::RequestExt;
5use http::header::CONTENT_TYPE;
6use http::StatusCode;
7use serde::de::DeserializeOwned;
8use serde::Serialize;
9
10/// URL encoded extractor and response.
11///
12/// # As extractor
13///
14/// If used as an extractor, `Form` will deserialize form data from the request,
15/// specifically:
16///
17/// - If the request has a method of `GET` or `HEAD`, the form data will be read
18///   from the query string (same as with [`Query`])
19/// - If the request has a different method, the form will be read from the body
20///   of the request. It must have a `content-type` of
21///   `application/x-www-form-urlencoded` for this to work. If you want to parse
22///   `multipart/form-data` request bodies, use [`Multipart`] instead.
23///
24/// This matches how HTML forms are sent by browsers by default.
25/// In both cases, the inner type `T` must implement [`serde::Deserialize`].
26///
27/// ⚠️ Since parsing form data might require consuming the request body, the `Form` extractor must be
28/// *last* if there are multiple extractors in a handler. See ["the order of
29/// extractors"][order-of-extractors]
30///
31/// [order-of-extractors]: crate::extract#the-order-of-extractors
32///
33/// ```rust
34/// use axum::Form;
35/// use serde::Deserialize;
36///
37/// #[derive(Deserialize)]
38/// struct SignUp {
39///     username: String,
40///     password: String,
41/// }
42///
43/// async fn accept_form(Form(sign_up): Form<SignUp>) {
44///     // ...
45/// }
46/// ```
47///
48/// # As response
49///
50/// `Form` can also be used to encode any type that implements
51/// [`serde::Serialize`] as `application/x-www-form-urlencoded`
52///
53/// ```rust
54/// use axum::Form;
55/// use serde::Serialize;
56///
57/// #[derive(Serialize)]
58/// struct Payload {
59///     value: String,
60/// }
61///
62/// async fn handler() -> Form<Payload> {
63///     Form(Payload { value: "foo".to_owned() })
64/// }
65/// ```
66///
67/// [`Query`]: crate::extract::Query
68/// [`Multipart`]: crate::extract::Multipart
69#[cfg_attr(docsrs, doc(cfg(feature = "form")))]
70#[derive(Debug, Clone, Copy, Default)]
71#[must_use]
72pub struct Form<T>(pub T);
73
74impl<T, S> FromRequest<S> for Form<T>
75where
76    T: DeserializeOwned,
77    S: Send + Sync,
78{
79    type Rejection = FormRejection;
80
81    async fn from_request(req: Request, _state: &S) -> Result<Self, Self::Rejection> {
82        let is_get_or_head =
83            req.method() == http::Method::GET || req.method() == http::Method::HEAD;
84
85        match req.extract().await {
86            Ok(RawForm(bytes)) => {
87                let deserializer =
88                    serde_urlencoded::Deserializer::new(form_urlencoded::parse(&bytes));
89                let value = serde_path_to_error::deserialize(deserializer).map_err(
90                    |err| -> FormRejection {
91                        if is_get_or_head {
92                            FailedToDeserializeForm::from_err(err).into()
93                        } else {
94                            FailedToDeserializeFormBody::from_err(err).into()
95                        }
96                    },
97                )?;
98                Ok(Form(value))
99            }
100            Err(RawFormRejection::BytesRejection(r)) => Err(FormRejection::BytesRejection(r)),
101            Err(RawFormRejection::InvalidFormContentType(r)) => {
102                Err(FormRejection::InvalidFormContentType(r))
103            }
104        }
105    }
106}
107
108impl<T> IntoResponse for Form<T>
109where
110    T: Serialize,
111{
112    fn into_response(self) -> Response {
113        match serde_urlencoded::to_string(&self.0) {
114            Ok(body) => (
115                [(CONTENT_TYPE, mime::APPLICATION_WWW_FORM_URLENCODED.as_ref())],
116                body,
117            )
118                .into_response(),
119            Err(err) => (StatusCode::INTERNAL_SERVER_ERROR, err.to_string()).into_response(),
120        }
121    }
122}
123
124axum_core::__impl_deref!(Form);
125
126#[cfg(test)]
127mod tests {
128    use crate::{
129        routing::{on, MethodFilter},
130        test_helpers::TestClient,
131        Router,
132    };
133
134    use super::*;
135    use axum_core::body::Body;
136    use http::{Method, Request};
137    use mime::APPLICATION_WWW_FORM_URLENCODED;
138    use serde::{Deserialize, Serialize};
139    use std::fmt::Debug;
140
141    #[derive(Debug, PartialEq, Serialize, Deserialize)]
142    struct Pagination {
143        size: Option<u64>,
144        page: Option<u64>,
145    }
146
147    async fn check_query<T: DeserializeOwned + PartialEq + Debug>(uri: impl AsRef<str>, value: T) {
148        let req = Request::builder()
149            .uri(uri.as_ref())
150            .body(Body::empty())
151            .unwrap();
152        assert_eq!(Form::<T>::from_request(req, &()).await.unwrap().0, value);
153    }
154
155    async fn check_body<T: Serialize + DeserializeOwned + PartialEq + Debug>(value: T) {
156        let req = Request::builder()
157            .uri("http://example.com/test")
158            .method(Method::POST)
159            .header(CONTENT_TYPE, APPLICATION_WWW_FORM_URLENCODED.as_ref())
160            .body(Body::from(serde_urlencoded::to_string(&value).unwrap()))
161            .unwrap();
162        assert_eq!(Form::<T>::from_request(req, &()).await.unwrap().0, value);
163    }
164
165    #[crate::test]
166    async fn test_form_query() {
167        check_query(
168            "http://example.com/test",
169            Pagination {
170                size: None,
171                page: None,
172            },
173        )
174        .await;
175
176        check_query(
177            "http://example.com/test?size=10",
178            Pagination {
179                size: Some(10),
180                page: None,
181            },
182        )
183        .await;
184
185        check_query(
186            "http://example.com/test?size=10&page=20",
187            Pagination {
188                size: Some(10),
189                page: Some(20),
190            },
191        )
192        .await;
193    }
194
195    #[crate::test]
196    async fn test_form_body() {
197        check_body(Pagination {
198            size: None,
199            page: None,
200        })
201        .await;
202
203        check_body(Pagination {
204            size: Some(10),
205            page: None,
206        })
207        .await;
208
209        check_body(Pagination {
210            size: Some(10),
211            page: Some(20),
212        })
213        .await;
214    }
215
216    #[crate::test]
217    async fn test_incorrect_content_type() {
218        let req = Request::builder()
219            .uri("http://example.com/test")
220            .method(Method::POST)
221            .header(CONTENT_TYPE, mime::APPLICATION_JSON.as_ref())
222            .body(Body::from(
223                serde_urlencoded::to_string(&Pagination {
224                    size: Some(10),
225                    page: None,
226                })
227                .unwrap(),
228            ))
229            .unwrap();
230        assert!(matches!(
231            Form::<Pagination>::from_request(req, &())
232                .await
233                .unwrap_err(),
234            FormRejection::InvalidFormContentType(InvalidFormContentType)
235        ));
236    }
237
238    #[tokio::test]
239    async fn deserialize_error_status_codes() {
240        #[allow(dead_code)]
241        #[derive(Deserialize)]
242        struct Payload {
243            a: i32,
244        }
245
246        let app = Router::new().route(
247            "/",
248            on(
249                MethodFilter::GET.or(MethodFilter::POST),
250                |_: Form<Payload>| async {},
251            ),
252        );
253
254        let client = TestClient::new(app);
255
256        let res = client.get("/?a=false").await;
257        assert_eq!(res.status(), StatusCode::BAD_REQUEST);
258        assert_eq!(
259            res.text().await,
260            "Failed to deserialize form: a: invalid digit found in string"
261        );
262
263        let res = client
264            .post("/")
265            .header(CONTENT_TYPE, APPLICATION_WWW_FORM_URLENCODED.as_ref())
266            .body("a=false")
267            .await;
268        assert_eq!(res.status(), StatusCode::UNPROCESSABLE_ENTITY);
269        assert_eq!(
270            res.text().await,
271            "Failed to deserialize form body: a: invalid digit found in string"
272        );
273    }
274}
axum/form.rs

axum/
form.rs
