Struct Router

pub struct Router<S = ()> { /* private fields */ }

The router type for composing handlers and services.

Implementations

impl<S> Router<S>

where S: Clone + Send + Sync + 'static,

pub fn new() -> Self

Create a new Router.

Unless you add additional routes this will respond with 404 Not Found to all requests.

pub fn route(self, path: &str, method_router: MethodRouter<S>) -> Self

Add another route to the router.

path is a string of path segments separated by /. Each segment can be either static, a capture, or a wildcard.

method_router is the MethodRouter that should receive the request if the path matches path. method_router will commonly be a handler wrapped in a method router like get. See handler for more details on handlers.

Static paths

Examples:

• /
• /foo
• /users/123

If the incoming request matches the path exactly the corresponding service will be called.

Captures

Paths can contain segments like /:key which matches any single segment and will store the value captured at key. The value captured can be zero-length except for in the invalid path //.

Examples:

• /:key
• /users/:id
• /users/:id/tweets

Captures can be extracted using Path. See its documentation for more details.

It is not possible to create segments that only match some types like numbers or regular expression. You must handle that manually in your handlers.

MatchedPath can be used to extract the matched path rather than the actual path.

Wildcards

Paths can end in /*key which matches all segments and will store the segments captured at key.

Examples:

• /*key
• /assets/*path
• /:id/:repo/*tree

Note that /*key doesn’t match empty segments. Thus:

• /*key doesn’t match / but does match /a, /a/, etc.
• /x/*key doesn’t match /x or /x/ but does match /x/a, /x/a/, etc.

Wildcard captures can also be extracted using Path:

use axum::{
    Router,
    routing::get,
    extract::Path,
};

let app: Router = Router::new().route("/*key", get(handler));

async fn handler(Path(path): Path<String>) -> String {
    path
}

Note that the leading slash is not included, i.e. for the route /foo/*rest and the path /foo/bar/baz the value of rest will be bar/baz.

Accepting multiple methods

To accept multiple methods for the same route you can add all handlers at the same time:

use axum::{Router, routing::{get, delete}, extract::Path};

let app = Router::new().route(
    "/",
    get(get_root).post(post_root).delete(delete_root),
);

async fn get_root() {}

async fn post_root() {}

async fn delete_root() {}

Or you can add them one by one:

let app = Router::new()
    .route("/", get(get_root))
    .route("/", post(post_root))
    .route("/", delete(delete_root));

More examples

use axum::{Router, routing::{get, delete}, extract::Path};

let app = Router::new()
    .route("/", get(root))
    .route("/users", get(list_users).post(create_user))
    .route("/users/:id", get(show_user))
    .route("/api/:version/users/:id/action", delete(do_users_action))
    .route("/assets/*path", get(serve_asset));

async fn root() {}

async fn list_users() {}

async fn create_user() {}

async fn show_user(Path(id): Path<u64>) {}

async fn do_users_action(Path((version, id)): Path<(String, u64)>) {}

async fn serve_asset(Path(path): Path<String>) {}

Panics

Panics if the route overlaps with another route:

use axum::{routing::get, Router};

let app = Router::new()
    .route("/", get(|| async {}))
    .route("/", get(|| async {}));

The static route /foo and the dynamic route /:key are not considered to overlap and /foo will take precedence.

Also panics if path is empty.

pub fn route_service<T>(self, path: &str, service: T) -> Self

where T: Service<Request, Error = Infallible> + Clone + Send + 'static, T::Response: IntoResponse, T::Future: Send + 'static,

Add another route to the router that calls a Service.

Example

use axum::{
    Router,
    body::Body,
    routing::{any_service, get_service},
    extract::Request,
    http::StatusCode,
    error_handling::HandleErrorLayer,
};
use tower_http::services::ServeFile;
use http::Response;
use std::{convert::Infallible, io};
use tower::service_fn;

let app = Router::new()
    .route(
        // Any request to `/` goes to a service
        "/",
        // Services whose response body is not `axum::body::BoxBody`
        // can be wrapped in `axum::routing::any_service` (or one of the other routing filters)
        // to have the response body mapped
        any_service(service_fn(|_: Request| async {
            let res = Response::new(Body::from("Hi from `GET /`"));
            Ok::<_, Infallible>(res)
        }))
    )
    .route_service(
        "/foo",
        // This service's response body is `axum::body::BoxBody` so
        // it can be routed to directly.
        service_fn(|req: Request| async move {
            let body = Body::from(format!("Hi from `{} /foo`", req.method()));
            let res = Response::new(body);
            Ok::<_, Infallible>(res)
        })
    )
    .route_service(
        // GET `/static/Cargo.toml` goes to a service from tower-http
        "/static/Cargo.toml",
        ServeFile::new("Cargo.toml"),
    );

Routing to arbitrary services in this way has complications for backpressure (Service::poll_ready). See the Routing to services and backpressure module for more details.

Panics

Panics for the same reasons as Router::route or if you attempt to route to a Router:

use axum::{routing::get, Router};

let app = Router::new().route_service(
    "/",
    Router::new().route("/foo", get(|| async {})),
);

Use Router::nest instead.

pub fn nest(self, path: &str, router: Router<S>) -> Self

Nest a Router at some path.

This allows you to break your application into smaller pieces and compose them together.

Example

use axum::{
    routing::{get, post},
    Router,
};

let user_routes = Router::new().route("/:id", get(|| async {}));

let team_routes = Router::new().route("/", post(|| async {}));

let api_routes = Router::new()
    .nest("/users", user_routes)
    .nest("/teams", team_routes);

let app = Router::new().nest("/api", api_routes);

// Our app now accepts
// - GET /api/users/:id
// - POST /api/teams

How the URI changes

Note that nested routes will not see the original request URI but instead have the matched prefix stripped. This is necessary for services like static file serving to work. Use OriginalUri if you need the original request URI.

Captures from outer routes

Take care when using nest together with dynamic routes as nesting also captures from the outer routes:

use axum::{
    extract::Path,
    routing::get,
    Router,
};
use std::collections::HashMap;

async fn users_get(Path(params): Path<HashMap<String, String>>) {
    // Both `version` and `id` were captured even though `users_api` only
    // explicitly captures `id`.
    let version = params.get("version");
    let id = params.get("id");
}

let users_api = Router::new().route("/users/:id", get(users_get));

let app = Router::new().nest("/:version/api", users_api);

Differences from wildcard routes

Nested routes are similar to wildcard routes. The difference is that wildcard routes still see the whole URI whereas nested routes will have the prefix stripped:

use axum::{routing::get, http::Uri, Router};

let nested_router = Router::new()
    .route("/", get(|uri: Uri| async {
        // `uri` will _not_ contain `/bar`
    }));

let app = Router::new()
    .route("/foo/*rest", get(|uri: Uri| async {
        // `uri` will contain `/foo`
    }))
    .nest("/bar", nested_router);

Additionally, while the wildcard route /foo/*rest will not match the paths /foo or /foo/, a nested router at /foo will match the path /foo (but not /foo/), and a nested router at /foo/ will match the path /foo/ (but not /foo).

Fallbacks

If a nested router doesn’t have its own fallback then it will inherit the fallback from the outer router:

use axum::{routing::get, http::StatusCode, handler::Handler, Router};

async fn fallback() -> (StatusCode, &'static str) {
    (StatusCode::NOT_FOUND, "Not Found")
}

let api_routes = Router::new().route("/users", get(|| async {}));

let app = Router::new()
    .nest("/api", api_routes)
    .fallback(fallback);

Here requests like GET /api/not-found will go into api_routes but because it doesn’t have a matching route and doesn’t have its own fallback it will call the fallback from the outer router, i.e. the fallback function.

If the nested router has its own fallback then the outer fallback will not be inherited:

use axum::{
    routing::get,
    http::StatusCode,
    handler::Handler,
    Json,
    Router,
};

async fn fallback() -> (StatusCode, &'static str) {
    (StatusCode::NOT_FOUND, "Not Found")
}

async fn api_fallback() -> (StatusCode, Json<serde_json::Value>) {
    (
        StatusCode::NOT_FOUND,
        Json(serde_json::json!({ "status": "Not Found" })),
    )
}

let api_routes = Router::new()
    .route("/users", get(|| async {}))
    .fallback(api_fallback);

let app = Router::new()
    .nest("/api", api_routes)
    .fallback(fallback);

Here requests like GET /api/not-found will go to api_fallback.

Nesting routers with state

When combining Routers with this method, each Router must have the same type of state. If your routers have different types you can use Router::with_state to provide the state and make the types match:

use axum::{
    Router,
    routing::get,
    extract::State,
};

#[derive(Clone)]
struct InnerState {}

#[derive(Clone)]
struct OuterState {}

async fn inner_handler(state: State<InnerState>) {}

let inner_router = Router::new()
    .route("/bar", get(inner_handler))
    .with_state(InnerState {});

async fn outer_handler(state: State<OuterState>) {}

let app = Router::new()
    .route("/", get(outer_handler))
    .nest("/foo", inner_router)
    .with_state(OuterState {});

Note that the inner router will still inherit the fallback from the outer router.

Panics

• If the route overlaps with another route. See Router::route for more details.
• If the route contains a wildcard (*).
• If path is empty.

pub fn nest_service<T>(self, path: &str, service: T) -> Self

where T: Service<Request, Error = Infallible> + Clone + Send + 'static, T::Response: IntoResponse, T::Future: Send + 'static,

Like nest, but accepts an arbitrary Service.

pub fn merge<R>(self, other: R) -> Self

where R: Into<Router<S>>,

Merge the paths and fallbacks of two routers into a single Router.

This is useful for breaking apps into smaller pieces and combining them into one.

use axum::{
    routing::get,
    Router,
};

// define some routes separately
let user_routes = Router::new()
    .route("/users", get(users_list))
    .route("/users/:id", get(users_show));

let team_routes = Router::new()
    .route("/teams", get(teams_list));

// combine them into one
let app = Router::new()
    .merge(user_routes)
    .merge(team_routes);

// could also do `user_routes.merge(team_routes)`

// Our app now accepts
// - GET /users
// - GET /users/:id
// - GET /teams

Merging routers with state

When combining Routers with this method, each Router must have the same type of state. If your routers have different types you can use Router::with_state to provide the state and make the types match:

use axum::{
    Router,
    routing::get,
    extract::State,
};

#[derive(Clone)]
struct InnerState {}

#[derive(Clone)]
struct OuterState {}

async fn inner_handler(state: State<InnerState>) {}

let inner_router = Router::new()
    .route("/bar", get(inner_handler))
    .with_state(InnerState {});

async fn outer_handler(state: State<OuterState>) {}

let app = Router::new()
    .route("/", get(outer_handler))
    .merge(inner_router)
    .with_state(OuterState {});

Merging routers with fallbacks

When combining Routers with this method, the fallback is also merged. However only one of the routers can have a fallback.

Panics

• If two routers that each have a fallback are merged. This is because Router only allows a single fallback.

pub fn layer<L>(self, layer: L) -> Router<S>

where L: Layer<Route> + Clone + Send + 'static, L::Service: Service<Request> + Clone + Send + 'static, <L::Service as Service<Request>>::Response: IntoResponse + 'static, <L::Service as Service<Request>>::Error: Into<Infallible> + 'static, <L::Service as Service<Request>>::Future: Send + 'static,

Apply a tower::Layer to all routes in the router.

This can be used to add additional processing to a request for a group of routes.

Note that the middleware is only applied to existing routes. So you have to first add your routes (and / or fallback) and then call layer afterwards. Additional routes added after layer is called will not have the middleware added.

If you want to add middleware to a single handler you can either use MethodRouter::layer or Handler::layer.

Example

Adding the [tower_http::trace::TraceLayer]:

use axum::{routing::get, Router};
use tower_http::trace::TraceLayer;

let app = Router::new()
    .route("/foo", get(|| async {}))
    .route("/bar", get(|| async {}))
    .layer(TraceLayer::new_for_http());

If you need to write your own middleware see “Writing middleware” for the different options.

If you only want middleware on some routes you can use Router::merge:

use axum::{routing::get, Router};
use tower_http::{trace::TraceLayer, compression::CompressionLayer};

let with_tracing = Router::new()
    .route("/foo", get(|| async {}))
    .layer(TraceLayer::new_for_http());

let with_compression = Router::new()
    .route("/bar", get(|| async {}))
    .layer(CompressionLayer::new());

// Merge everything into one `Router`
let app = Router::new()
    .merge(with_tracing)
    .merge(with_compression);

Multiple middleware

It’s recommended to use tower::ServiceBuilder when applying multiple middleware. See middleware for more details.

Runs after routing

Middleware added with this method will run after routing and thus cannot be used to rewrite the request URI. See “Rewriting request URI in middleware” for more details and a workaround.

Error handling

See middleware for details on how error handling impacts middleware.

pub fn route_layer<L>(self, layer: L) -> Self

where L: Layer<Route> + Clone + Send + 'static, L::Service: Service<Request> + Clone + Send + 'static, <L::Service as Service<Request>>::Response: IntoResponse + 'static, <L::Service as Service<Request>>::Error: Into<Infallible> + 'static, <L::Service as Service<Request>>::Future: Send + 'static,

Apply a tower::Layer to the router that will only run if the request matches a route.

Note that the middleware is only applied to existing routes. So you have to first add your routes (and / or fallback) and then call route_layer afterwards. Additional routes added after route_layer is called will not have the middleware added.

This works similarly to Router::layer except the middleware will only run if the request matches a route. This is useful for middleware that return early (such as authorization) which might otherwise convert a 404 Not Found into a 401 Unauthorized.

This function will panic if no routes have been declared yet on the router, since the new layer will have no effect, and this is typically a bug. In generic code, you can test if that is the case first, by calling Router::has_routes.

Example

use axum::{
    routing::get,
    Router,
};
use tower_http::validate_request::ValidateRequestHeaderLayer;

let app = Router::new()
    .route("/foo", get(|| async {}))
    .route_layer(ValidateRequestHeaderLayer::bearer("password"));

// `GET /foo` with a valid token will receive `200 OK`
// `GET /foo` with a invalid token will receive `401 Unauthorized`
// `GET /not-found` with a invalid token will receive `404 Not Found`

pub fn has_routes(&self) -> bool

True if the router currently has at least one route added.

pub fn fallback<H, T>(self, handler: H) -> Self

where H: Handler<T, S>, T: 'static,

Add a fallback Handler to the router.

This service will be called if no routes matches the incoming request.

use axum::{
    Router,
    routing::get,
    handler::Handler,
    response::IntoResponse,
    http::{StatusCode, Uri},
};

let app = Router::new()
    .route("/foo", get(|| async { /* ... */ }))
    .fallback(fallback);

async fn fallback(uri: Uri) -> (StatusCode, String) {
    (StatusCode::NOT_FOUND, format!("No route for {uri}"))
}

Fallbacks only apply to routes that aren’t matched by anything in the router. If a handler is matched by a request but returns 404 the fallback is not called. Note that this applies to MethodRouters too: if the request hits a valid path but the MethodRouter does not have an appropriate method handler installed, the fallback is not called (use MethodRouter::fallback for this purpose instead).

Handling all requests without other routes

Using Router::new().fallback(...) to accept all request regardless of path or method, if you don’t have other routes, isn’t optimal:

use axum::Router;

async fn handler() {}

let app = Router::new().fallback(handler);

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, app).await.unwrap();

Running the handler directly is faster since it avoids the overhead of routing:

use axum::handler::HandlerWithoutStateExt;

async fn handler() {}

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, handler.into_make_service()).await.unwrap();

pub fn fallback_service<T>(self, service: T) -> Self

where T: Service<Request, Error = Infallible> + Clone + Send + 'static, T::Response: IntoResponse, T::Future: Send + 'static,

Add a fallback Service to the router.

See Router::fallback for more details.

pub fn with_state<S2>(self, state: S) -> Router<S2>

Provide the state for the router.

use axum::{Router, routing::get, extract::State};

#[derive(Clone)]
struct AppState {}

let routes = Router::new()
    .route("/", get(|State(state): State<AppState>| async {
        // use state
    }))
    .with_state(AppState {});

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, routes).await.unwrap();

Returning routers with states from functions

When returning Routers from functions, it is generally recommended not to set the state directly:

use axum::{Router, routing::get, extract::State};

#[derive(Clone)]
struct AppState {}

// Don't call `Router::with_state` here
fn routes() -> Router<AppState> {
    Router::new()
        .route("/", get(|_: State<AppState>| async {}))
}

// Instead do it before you run the server
let routes = routes().with_state(AppState {});

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, routes).await.unwrap();

If you do need to provide the state, and you’re not nesting/merging the router into another router, then return Router without any type parameters:

// Don't return `Router<AppState>`
fn routes(state: AppState) -> Router {
    Router::new()
        .route("/", get(|_: State<AppState>| async {}))
        .with_state(state)
}

let routes = routes(AppState {});

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, routes).await.unwrap();

This is because we can only call Router::into_make_service on Router<()>, not Router<AppState>. See below for more details about why that is.

Note that the state defaults to () so Router and Router<()> is the same.

If you are nesting/merging the router it is recommended to use a generic state type on the resulting router:

fn routes<S>(state: AppState) -> Router<S> {
    Router::new()
        .route("/", get(|_: State<AppState>| async {}))
        .with_state(state)
}

let routes = Router::new().nest("/api", routes(AppState {}));

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, routes).await.unwrap();

State is global within the router

The state passed to this method will be used for all requests this router receives. That means it is not suitable for holding state derived from a request, such as authorization data extracted in a middleware. Use Extension instead for such data.

What S in Router<S> means

Router<S> means a router that is missing a state of type S to be able to handle requests. It does not mean a Router that has a state of type S.

For example:

// A router that _needs_ an `AppState` to handle requests
let router: Router<AppState> = Router::new()
    .route("/", get(|_: State<AppState>| async {}));

// Once we call `Router::with_state` the router isn't missing
// the state anymore, because we just provided it
//
// Therefore the router type becomes `Router<()>`, i.e a router
// that is not missing any state
let router: Router<()> = router.with_state(AppState {});

// Only `Router<()>` has the `into_make_service` method.
//
// You cannot call `into_make_service` on a `Router<AppState>`
// because it is still missing an `AppState`.
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, router).await.unwrap();

Perhaps a little counter intuitively, Router::with_state doesn’t always return a Router<()>. Instead you get to pick what the new missing state type is:

let router: Router<AppState> = Router::new()
    .route("/", get(|_: State<AppState>| async {}));

// When we call `with_state` we're able to pick what the next missing state type is.
// Here we pick `String`.
let string_router: Router<String> = router.with_state(AppState {});

// That allows us to add new routes that uses `String` as the state type
let string_router = string_router
    .route("/needs-string", get(|_: State<String>| async {}));

// Provide the `String` and choose `()` as the new missing state.
let final_router: Router<()> = string_router.with_state("foo".to_owned());

// Since we have a `Router<()>` we can run it.
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, final_router).await.unwrap();

This why this returning Router<AppState> after calling with_state doesn’t work:

// This won't work because we're returning a `Router<AppState>`
// i.e. we're saying we're still missing an `AppState`
fn routes(state: AppState) -> Router<AppState> {
    Router::new()
        .route("/", get(|_: State<AppState>| async {}))
        .with_state(state)
}

let app = routes(AppState {});

// We can only call `Router::into_make_service` on a `Router<()>`
// but `app` is a `Router<AppState>`
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, app).await.unwrap();

Instead return Router<()> since we have provided all the state needed:

// We've provided all the state necessary so return `Router<()>`
fn routes(state: AppState) -> Router<()> {
    Router::new()
        .route("/", get(|_: State<AppState>| async {}))
        .with_state(state)
}

let app = routes(AppState {});

// We can now call `Router::into_make_service`
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, app).await.unwrap();

A note about performance

If you need a Router that implements Service but you don’t need any state (perhaps you’re making a library that uses axum internally) then it is recommended to call this method before you start serving requests:

use axum::{Router, routing::get};

let app = Router::new()
    .route("/", get(|| async { /* ... */ }))
    // even though we don't need any state, call `with_state(())` anyway
    .with_state(());

This is not required but it gives axum a chance to update some internals in the router which may impact performance and reduce allocations.

Note that Router::into_make_service and [Router::into_make_service_with_connect_info] do this automatically.

pub fn as_service<B>(&mut self) -> RouterAsService<'_, B, S>

Convert the router into a borrowed Service with a fixed request body type, to aid type inference.

In some cases when calling methods from tower::ServiceExt on a Router you might get type inference errors along the lines of

let response = router.ready().await?.call(request).await?;
                      ^^^^^ cannot infer type for type parameter `B`

This happens because Router implements Service with impl<B> Service<Request<B>> for Router<()>.

For example:

use axum::{
    Router,
    routing::get,
    http::Request,
    body::Body,
};
use tower::{Service, ServiceExt};

let mut router = Router::new().route("/", get(|| async {}));
let request = Request::new(Body::empty());
let response = router.ready().await?.call(request).await?;

Calling Router::as_service fixes that:

use axum::{
    Router,
    routing::get,
    http::Request,
    body::Body,
};
use tower::{Service, ServiceExt};

let mut router = Router::new().route("/", get(|| async {}));
let request = Request::new(Body::empty());
let response = router.as_service().ready().await?.call(request).await?;

This is mainly used when calling Router in tests. It shouldn’t be necessary when running the Router normally via Router::into_make_service.

pub fn into_service<B>(self) -> RouterIntoService<B, S>

Convert the router into an owned Service with a fixed request body type, to aid type inference.

This is the same as Router::as_service instead it returns an owned Service. See that method for more details.

impl Router

pub fn into_make_service(self) -> IntoMakeService<Self>

Convert this router into a MakeService, that is a Service whose response is another service.

use axum::{
    routing::get,
    Router,
};

let app = Router::new().route("/", get(|| async { "Hi!" }));

let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, app).await.unwrap();

Trait Implementations

impl<S> Clone for Router<S>

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl<S> Debug for Router<S>

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

Formats the value using the given formatter.

impl<S> Default for Router<S>

where S: Clone + Send + Sync + 'static,

fn default() -> Self

Returns the “default value” for a type.

impl<B> Service<Request<B>> for Router<()>

where B: HttpBody<Data = Bytes> + Send + 'static, B::Error: Into<BoxError>,

type Response = Response<Body>

Responses given by the service.

type Error = Infallible

Errors produced by the service.

type Future = RouteFuture<Infallible>

The future response value.

fn poll_ready(&mut self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

Returns Poll::Ready(Ok(())) when the service is able to process requests.

fn call(&mut self, req: Request<B>) -> Self::Future

Process the request and return the response asynchronously.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 8 bytes