Struct actix_web::App

pub struct App<T> { /* private fields */ }

Application builder - structure that follows the builder pattern for building application instances.

Implementations

impl App<AppEntry>

pub fn new() -> Self

Create application builder. Application can be configured with a builder-like pattern.

impl<T> App<T> where
    T: ServiceFactory<ServiceRequest, Config = (), Error = Error, InitError = ()>, 

pub fn app_data<U: 'static>(self, ext: U) -> Self

Set application (root level) data.

Application data stored with App::app_data() method is available through the HttpRequest::app_data method at runtime.

Data<T>

Any Data<T> type added here can utilize it’s extractor implementation in handlers. Types not wrapped in Data<T> cannot use this extractor. See its docs for more about its usage and patterns.

use std::cell::Cell;
use actix_web::{web, App, HttpRequest, HttpResponse, Responder};

struct MyData {
    count: std::cell::Cell<usize>,
}

async fn handler(req: HttpRequest, counter: web::Data<MyData>) -> impl Responder {
    // note this cannot use the Data<T> extractor because it was not added with it
    let incr = *req.app_data::<usize>().unwrap();
    assert_eq!(incr, 3);

    // update counter using other value from app data
    counter.count.set(counter.count.get() + incr);

    HttpResponse::Ok().body(counter.count.get().to_string())
}

let app = App::new().service(
    web::resource("/")
        .app_data(3usize)
        .app_data(web::Data::new(MyData { count: Default::default() }))
        .route(web::get().to(handler))
);

Shared Mutable State

HttpServer::new accepts an application factory rather than an application instance; the factory closure is called on each worker thread independently. Therefore, if you want to share a data object between different workers, a shareable object needs to be created first, outside the HttpServer::new closure and cloned into it. Data<T> is an example of such a sharable object.

let counter = web::Data::new(AppStateWithCounter {
    counter: Mutex::new(0),
});

HttpServer::new(move || {
    // move counter object into the closure and clone for each worker

    App::new()
        .app_data(counter.clone())
        .route("/", web::get().to(handler))
})

pub fn data<U: 'static>(self, data: U) -> Self

👎 Deprecated since 4.0.0:

Use .app_data(Data::new(val)) instead.

Add application (root) data after wrapping in Data<T>.

Deprecated in favor of app_data.

pub fn data_factory<F, Out, D, E>(self, data: F) -> Self where
    F: Fn() -> Out + 'static,
    Out: Future<Output = Result<D, E>> + 'static,
    D: 'static,
    E: Debug, 

Add application data factory that resolves asynchronously.

Data items are constructed during application initialization, before the server starts accepting requests.

pub fn configure<F>(self, f: F) -> Self where
    F: FnOnce(&mut ServiceConfig), 

Run external configuration as part of the application building process

This function is useful for moving parts of configuration to a different module or even library. For example, some of the resource’s configuration could be moved to different module.

use actix_web::{web, App, HttpResponse};

// this function could be located in different module
fn config(cfg: &mut web::ServiceConfig) {
    cfg.service(web::resource("/test")
        .route(web::get().to(|| HttpResponse::Ok()))
        .route(web::head().to(|| HttpResponse::MethodNotAllowed()))
    );
}

App::new()
    .configure(config)  // <- register resources
    .route("/index.html", web::get().to(|| HttpResponse::Ok()));

pub fn route(self, path: &str, route: Route) -> Self

Configure route for a specific path.

This is a simplified version of the App::service() method. This method can be used multiple times with same path, in that case multiple resources with one route would be registered for same resource path.

use actix_web::{web, App, HttpResponse};

async fn index(data: web::Path<(String, String)>) -> &'static str {
    "Welcome!"
}

let app = App::new()
    .route("/test1", web::get().to(index))
    .route("/test2", web::post().to(|| HttpResponse::MethodNotAllowed()));

pub fn service<F>(self, factory: F) -> Self where
    F: HttpServiceFactory + 'static, 

Register HTTP service.

Http service is any type that implements HttpServiceFactory trait.

Actix Web provides several services implementations:

• Resource is an entry in resource table which corresponds to requested URL.
• Scope is a set of resources with common root path.
• “StaticFiles” is a service for static files support

pub fn default_service<F, U>(self, svc: F) -> Self where
    F: IntoServiceFactory<U, ServiceRequest>,
    U: ServiceFactory<ServiceRequest, Config = (), Response = ServiceResponse, Error = Error> + 'static,
    U::InitError: Debug, 

Default service that is invoked when no matching resource could be found.

You can use a Route as default service.

If a default service is not registered, an empty 404 Not Found response will be sent to the client instead.

Examples

use actix_web::{web, App, HttpResponse};

async fn index() -> &'static str {
    "Welcome!"
}

let app = App::new()
    .service(web::resource("/index.html").route(web::get().to(index)))
    .default_service(web::to(|| HttpResponse::NotFound()));

pub fn external_resource<N, U>(self, name: N, url: U) -> Self where
    N: AsRef<str>,
    U: AsRef<str>, 

Register an external resource.

External resources are useful for URL generation purposes only and are never considered for matching at request time. Calls to HttpRequest::url_for() will work as expected.

use actix_web::{web, App, HttpRequest, HttpResponse, Result};

async fn index(req: HttpRequest) -> Result<HttpResponse> {
    let url = req.url_for("youtube", &["asdlkjqme"])?;
    assert_eq!(url.as_str(), "https://youtube.com/watch/asdlkjqme");
    Ok(HttpResponse::Ok().into())
}

fn main() {
    let app = App::new()
        .service(web::resource("/index.html").route(
            web::get().to(index)))
        .external_resource("youtube", "https://youtube.com/watch/{video_id}");
}

pub fn wrap<M, B>(
    self,
    mw: M
) -> App<impl ServiceFactory<ServiceRequest, Config = (), Response = ServiceResponse<B>, Error = Error, InitError = ()>> where
    M: Transform<T::Service, ServiceRequest, Response = ServiceResponse<B>, Error = Error, InitError = ()> + 'static,
    B: MessageBody, 

Registers an app-wide middleware.

Registers middleware, in the form of a middleware compo nen t (type), that runs during inbound and/or outbound processing in the request life-cycle (request -> response), modifying request/response as necessary, across all requests managed by the App.

Use middleware when you need to read or modify every request or response in some way.

Middleware can be applied similarly to individual Scopes and Resources. See Scope::wrap and Resource::wrap.

Middleware Order

Notice that the keyword for registering middleware is wrap. As you register middleware using wrap in the App builder, imagine wrapping layers around an inner App. The first middleware layer exposed to a Request is the outermost layer (i.e., the last registered in the builder chain). Consequently, the first middleware registered in the builder chain is the last to start executing during request processing.

Ordering is less obvious when wrapped services also have middleware applied. In this case, middlewares are run in reverse order for App and then in reverse order for the wrapped service.

Examples

use actix_web::{middleware, web, App};

async fn index() -> &'static str {
    "Welcome!"
}

let app = App::new()
    .wrap(middleware::Logger::default())
    .route("/index.html", web::get().to(index));

pub fn wrap_fn<F, R, B>(
    self,
    mw: F
) -> App<impl ServiceFactory<ServiceRequest, Config = (), Response = ServiceResponse<B>, Error = Error, InitError = ()>> where
    F: Fn(ServiceRequest, &T::Service) -> R + Clone + 'static,
    R: Future<Output = Result<ServiceResponse<B>, Error>>,
    B: MessageBody, 

Registers an app-wide function middleware.

mw is a closure that runs during inbound and/or outbound processing in the request life-cycle (request -> response), modifying request/response as necessary, across all requests handled by the App.

Use middleware when you need to read or modify every request or response in some way.

Middleware can also be applied to individual Scopes and Resources.

See App::wrap for details on how middlewares compose with each other.

Examples

use actix_web::{dev::Service as _, middleware, web, App};
use actix_web::http::header::{CONTENT_TYPE, HeaderValue};

async fn index() -> &'static str {
    "Welcome!"
}

let app = App::new()
    .wrap_fn(|req, srv| {
        let fut = srv.call(req);
        async {
            let mut res = fut.await?;
            res.headers_mut()
                .insert(CONTENT_TYPE, HeaderValue::from_static("text/plain"));
            Ok(res)
        }
    })
    .route("/index.html", web::get().to(index));