Struct ErrorHandlers

pub struct ErrorHandlers<B> { /* private fields */ }

Middleware for registering custom status code based error handlers.

Register handlers with the ErrorHandlers::handler() method to register a custom error handler for a given status code. Handlers can modify existing responses or create completely new ones.

To register a default handler, use the ErrorHandlers::default_handler() method. This handler will be used only if a response has an error status code (400-599) that isn’t covered by a more specific handler (set with the handler() method). See examples below.

To register a default for only client errors (400-499) or only server errors (500-599), use the ErrorHandlers::default_handler_client() and ErrorHandlers::default_handler_server() methods, respectively.

Any response with a status code that isn’t covered by a specific handler or a default handler will pass by unchanged by this middleware.

Examples

Adding a header:

use actix_web::{
    dev::ServiceResponse,
    http::{header, StatusCode},
    middleware::{ErrorHandlerResponse, ErrorHandlers},
    web, App, HttpResponse, Result,
};

fn add_error_header<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
    res.response_mut().headers_mut().insert(
        header::CONTENT_TYPE,
        header::HeaderValue::from_static("Error"),
    );

    // body is unchanged, map to "left" slot
    Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
}

let app = App::new()
    .wrap(ErrorHandlers::new().handler(StatusCode::INTERNAL_SERVER_ERROR, add_error_header))
    .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));

Modifying response body:

use actix_web::{
    dev::ServiceResponse,
    http::{header, StatusCode},
    middleware::{ErrorHandlerResponse, ErrorHandlers},
    web, App, HttpResponse, Result,
};

fn add_error_body<B>(res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
    // split service response into request and response components
    let (req, res) = res.into_parts();

    // set body of response to modified body
    let res = res.set_body("An error occurred.");

    // modified bodies need to be boxed and placed in the "right" slot
    let res = ServiceResponse::new(req, res)
        .map_into_boxed_body()
        .map_into_right_body();

    Ok(ErrorHandlerResponse::Response(res))
}

let app = App::new()
    .wrap(ErrorHandlers::new().handler(StatusCode::INTERNAL_SERVER_ERROR, add_error_body))
    .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));

Registering default handler:

fn add_error_header<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
    res.response_mut().headers_mut().insert(
        header::CONTENT_TYPE,
        header::HeaderValue::from_static("Error"),
    );

    // body is unchanged, map to "left" slot
    Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
}

fn handle_bad_request<B>(mut res: ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> {
    res.response_mut().headers_mut().insert(
        header::CONTENT_TYPE,
        header::HeaderValue::from_static("Bad Request Error"),
    );

    // body is unchanged, map to "left" slot
    Ok(ErrorHandlerResponse::Response(res.map_into_left_body()))
}

// Bad Request errors will hit `handle_bad_request()`, while all other errors will hit
// `add_error_header()`. The order in which the methods are called is not meaningful.
let app = App::new()
    .wrap(
        ErrorHandlers::new()
            .default_handler(add_error_header)
            .handler(StatusCode::BAD_REQUEST, handle_bad_request)
    )
    .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));

You can set default handlers for all client (4xx) or all server (5xx) errors:

// Bad request errors will hit `handle_bad_request()`, other client errors will hit
// `add_error_header()`, and server errors will pass through unchanged
let app = App::new()
    .wrap(
        ErrorHandlers::new()
            .default_handler_client(add_error_header) // or .default_handler_server
            .handler(StatusCode::BAD_REQUEST, handle_bad_request)
    )
    .service(web::resource("/").route(web::get().to(HttpResponse::InternalServerError)));

Implementations

impl<B> ErrorHandlers<B>

pub fn new() -> Self

Construct new ErrorHandlers instance.

pub fn handler<F>(self, status: StatusCode, handler: F) -> Self

where F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,

Register error handler for specified status code.

pub fn default_handler<F>(self, handler: F) -> Self

where F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,

Register a default error handler.

Any request with a status code that hasn’t been given a specific other handler (by calling .handler()) will fall back on this.

Note that this will overwrite any default handlers previously set by calling default_handler_client() or .default_handler_server(), but not any set by calling .handler().

pub fn default_handler_client<F>(self, handler: F) -> Self

where F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,

Register a handler on which to fall back for client error status codes (400-499).

pub fn default_handler_server<F>(self, handler: F) -> Self

where F: Fn(ServiceResponse<B>) -> Result<ErrorHandlerResponse<B>> + 'static,

Register a handler on which to fall back for server error status codes (500-599).

Trait Implementations

impl<B> Default for ErrorHandlers<B>

fn default() -> Self

Returns the “default value” for a type.

impl<S, B> Transform<S, ServiceRequest> for ErrorHandlers<B>

where S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static, S::Future: 'static, B: 'static,

type Response = ServiceResponse<EitherBody<B>>

Responses produced by the service.

type Error = Error

Errors produced by the service.

type Transform = ErrorHandlersMiddleware<S, B>

The TransformService value created by this factory

type InitError = ()

Errors produced while building a transform service.

type Future = Pin<Box<dyn Future<Output = Result<<ErrorHandlers<B> as Transform<S, ServiceRequest>>::Transform, <ErrorHandlers<B> as Transform<S, ServiceRequest>>::InitError>>>>

The future response value.

fn new_transform(&self, service: S) -> Self::Future

Creates and returns a new Transform component, asynchronously