Struct ValidationExtractor

pub struct ValidationExtractor<T>(pub T);

A wrapper type that validates incoming JSON request bodies against a set of validation rules.

This extractor combines JSON deserialization with automatic validation using the validator crate. It’s designed to be used as a request extractor in Axum route handlers.

Type Parameters

• T - The type to deserialize the JSON into. Must implement both DeserializeOwned and Validate.

Examples

use serde::Deserialize;
use validator::Validate;

#[derive(Deserialize, Validate)]
struct CreateUser {
    #[validate(length(min = 3, max = 50))]
    username: String,
    #[validate(email)]
    email: String,
}

async fn create_user(
    ValidationExtractor(payload): ValidationExtractor<CreateUser>
) -> impl Response {
    // payload is guaranteed to be valid here
    // ...
}

Validation Flow

1. The incoming request body is first deserialized as JSON into type T
2. The deserialized value is validated using its Validate implementation
3. If both steps succeed, the value is wrapped in ValidationExtractor and passed to the handler
4. If either step fails, an error is returned and the handler is not called

Tuple Fields

0: T

Trait Implementations

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

where T: DeserializeOwned + Validate, S: Send + Sync, Json<T>: FromRequest<S, Rejection = JsonRejection>,

Implementation of FromRequest for ValidationExtractor<T>.

This implementation enables automatic extraction and validation of JSON request bodies in Axum route handlers.

Type Parameters

• T - The type to deserialize and validate (must implement DeserializeOwned and Validate)
• S - The state type for the Axum application

Errors

Returns an error in the following cases:

• JSON deserialization fails
• Validation rules are not satisfied

type Rejection = Error

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

fn from_request<'life0, 'async_trait>( req: Request, state: &'life0 S, ) -> Pin<Box<dyn Future<Output = Result<Self, Self::Rejection>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Perform the extraction.