Struct Json

pub struct Json<T>(pub T);

JSON Extractor / Response.

When used as an extractor, it can deserialize request bodies into some type that implements serde::de::DeserializeOwned. The request will be rejected (and a JsonRejection will be returned) if:

• The request doesn’t have a Content-Type: application/json (or similar) header.
• The body doesn’t contain syntactically valid JSON.
• The body contains syntactically valid JSON, but it couldn’t be deserialized into the target type.
• Buffering the request body fails.

⚠️ Since parsing JSON requires consuming the request body, the Json extractor must be last if there are multiple extractors in a handler. See “the order of extractors”

See JsonRejection for more details.

Extractor example

use axum::{
    extract,
    routing::post,
    Router,
};
use serde::Deserialize;

#[derive(Deserialize)]
struct CreateUser {
    email: String,
    password: String,
}

async fn create_user(extract::Json(payload): extract::Json<CreateUser>) {
    // payload is a `CreateUser`
}

let app = Router::new().route("/users", post(create_user));

When used as a response, it can serialize any type that implements serde::Serialize to JSON, and will automatically set Content-Type: application/json header.

If the Serialize implementation decides to fail or if a map with non-string keys is used, a 500 response will be issued whose body is the error message in UTF-8.

Response example

use axum::{
    extract::Path,
    routing::get,
    Router,
    Json,
};
use serde::Serialize;
use uuid::Uuid;

#[derive(Serialize)]
struct User {
    id: Uuid,
    username: String,
}

async fn get_user(Path(user_id) : Path<Uuid>) -> Json<User> {
    let user = find_user(user_id).await;
    Json(user)
}

async fn find_user(user_id: Uuid) -> User {
    // ...
}

let app = Router::new().route("/users/{id}", get(get_user));

Tuple Fields

0: T

Implementations

impl<T> Json<T>

where T: DeserializeOwned,

pub fn from_bytes(bytes: &[u8]) -> Result<Self, JsonRejection>

Construct a Json<T> from a byte slice. Most users should prefer to use the FromRequest impl but special cases may require first extracting a Request into Bytes then optionally constructing a Json<T>.

Trait Implementations

impl<T: Clone> Clone for Json<T>

fn clone(&self) -> Json<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Json<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T: Default> Default for Json<T>

fn default() -> Json<T>

Returns the “default value” for a type.

impl<T> Deref for Json<T>

type Target = T

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl<T> DerefMut for Json<T>

fn deref_mut(&mut self) -> &mut Self::Target

Mutably dereferences the value.

impl<T> From<T> for Json<T>

fn from(inner: T) -> Self

Converts to this type from the input type.

impl<T, S> FromRequest<S> for Json<T>

where T: DeserializeOwned, S: Send + Sync,

type Rejection = JsonRejection

If the extractor fails it’ll use this “rejection” type. A rejection is a kind of error that can be converted into a response.

async fn from_request(req: Request, state: &S) -> Result<Self, Self::Rejection>

Perform the extraction.

impl<T> IntoResponse for Json<T>

where T: Serialize,

fn into_response(self) -> Response

Create a response.

impl<T, S> OptionalFromRequest<S> for Json<T>

where T: DeserializeOwned, S: Send + Sync,

type Rejection = JsonRejection

If the extractor fails, it will use this “rejection” type.

async fn from_request( req: Request, state: &S, ) -> Result<Option<Self>, Self::Rejection>

Perform the extraction.

impl<T: Copy> Copy for Json<T>