
axum-web-framework
Complete guide for Axum web framework including routing, extractors, middleware, state management, error handling, and production deployment
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Axum Web Framework
A comprehensive skill for building production-ready web applications and APIs using Axum, the ergonomic and modular Rust web framework built on Tokio and Tower. Master routing, extractors, middleware, state management, error handling, and deployment patterns.
When to Use This Skill
Use this skill when:
- Building REST APIs with Rust and async/await
- Creating high-performance web services with type safety
- Developing microservices with Tokio ecosystem integration
- Implementing WebSocket servers or Server-Sent Events (SSE)
- Building GraphQL APIs with Rust backend
- Creating middleware-heavy applications requiring Tower integration
- Developing production-ready web applications requiring robust error handling
- Building systems requiring fine-grained control over HTTP request/response handling
- Implementing authentication, authorization, and security middleware
- Creating real-time web applications with async Rust
- Developing APIs requiring request validation and transformation
- Building web services with complex routing and nested routers
- Implementing rate limiting, timeout, and backpressure handling
- Creating web applications requiring custom extractors and response types
Core Concepts
Axum Architecture Philosophy
Axum is built on three fundamental pillars:
- Tower Services: Everything in Axum is built on Tower's
Servicetrait, providing composability and middleware integration - Type-Safe Extractors: Request data extraction is compile-time checked, eliminating runtime parsing errors
- Minimal Boilerplate: Ergonomic APIs that reduce ceremony while maintaining explicitness
The Router
The Router is the central building block in Axum. It maps HTTP requests to handlers based on path and method.
Key Properties:
- Routes are matched in the order they're defined
- Routers can be nested for modular organization
- Middleware can be applied at router, route, or method level
- Generic over state type for flexible state management
- Implements Tower's
Servicetrait for composability
Router Creation:
use axum::{Router, routing::get};
let app = Router::new()
.route("/", get(handler))
.route("/users/:id", get(get_user))
.route("/posts", get(list_posts).post(create_post));
Handlers
Handlers are async functions that process requests and return responses. Axum supports multiple handler signatures through its powerful type system.
Handler Requirements:
- Must be async functions
- Can extract data from requests using extractors
- Must return types implementing
IntoResponse - Can have up to 16 parameters (all must be extractors)
Common Handler Patterns:
// Simple handler
async fn handler() -> &'static str {
"Hello, World!"
}
// Handler with path parameter
async fn get_user(Path(user_id): Path<u32>) -> String {
format!("User ID: {}", user_id)
}
// Handler with multiple extractors
async fn create_user(
State(state): State<AppState>,
Json(payload): Json<CreateUser>,
) -> Result<Json<User>, StatusCode> {
// Implementation
}
Extractors
Extractors are types that implement FromRequest or FromRequestParts, allowing type-safe extraction of data from requests.
Built-in Extractors:
- Path - Extract path parameters
- Query - Extract query string parameters
- Json - Parse JSON request body
- Form - Parse form-encoded request body
- State - Access shared application state
- Extension - Access request extensions
- Headers - Access request headers
- Method - Get HTTP method
- Uri - Get request URI
- Request - Get full request
- Bytes - Raw request body as bytes
- String - Request body as UTF-8 string
- Multipart - Handle multipart/form-data
Extractor Ordering:
- Extractors that consume the request body must come last
- Multiple body extractors in one handler will cause compilation errors
Stateand other non-body extractors can be in any order
Responses
Any type implementing IntoResponse can be returned from handlers. Axum provides many built-in implementations.
Built-in Response Types:
String,&'static str- Text responsesJson<T>- JSON responsesHtml<String>- HTML responsesStatusCode- Status-only responses(StatusCode, T)- Status with body(Parts, T)- Custom headers with bodyResponse- Full control over responseResult<T, E>- Error handling (where E: IntoResponse)
State Management
Axum uses the State extractor to share data across handlers. State must implement Clone and is typically wrapped in Arc for shared ownership.
State Patterns:
- Simple State:
#[derive(Clone)]
struct AppState {
api_key: String,
}
let app = Router::new()
.route("/", get(handler))
.with_state(AppState {
api_key: "secret".to_string(),
});
- Shared State with Arc:
#[derive(Clone)]
struct AppState {
db_pool: Arc<DatabasePool>,
cache: Arc<RwLock<Cache>>,
}
- Multiple State Types:
// Define separate state types for different router sections
let api_router: Router<ApiState> = Router::new()
.route("/api/data", get(api_handler));
let app_router: Router<AppState> = Router::new()
.route("/app", get(app_handler));
// Combine with final state
let app = Router::new()
.nest("/", app_router.with_state(app_state))
.nest("/", api_router.with_state(api_state));
Middleware
Middleware in Axum comes from Tower and provides request/response transformation, logging, authentication, and more.
Middleware Categories:
- Tower Middleware - From
towerandtower-httpcrates - Custom Middleware - Using
middleware::from_fn - Service Middleware - Implementing Tower's
Servicetrait - Layer Pattern - Using Tower's
Layerfor composability
Middleware Application Order:
- Applied with
.layer()executes bottom-to-top (wrapping previous layers) - Applied with
ServiceBuilderexecutes top-to-bottom (more intuitive) - Middleware on
Router::layerruns after routing - Middleware around
Router(usingLayer::layer) runs before routing
Error Handling
Axum's error handling is built on the IntoResponse trait, allowing custom error types to be converted to HTTP responses.
Error Handling Strategies:
- Result Types:
async fn handler() -> Result<Json<Data>, StatusCode> {
// Returns 200 OK or error status code
}
- Custom Error Types:
enum AppError {
Database(sqlx::Error),
NotFound,
Unauthorized,
}
impl IntoResponse for AppError {
fn into_response(self) -> Response {
// Convert to HTTP response
}
}
- HandleErrorLayer:
use axum::error_handling::HandleErrorLayer;
let app = Router::new()
.layer(
ServiceBuilder::new()
.layer(HandleErrorLayer::new(handle_error))
.layer(TimeoutLayer::new(Duration::from_secs(30)))
);
Tower Integration
Axum is built on Tower, enabling powerful middleware composition and service abstraction.
Key Tower Concepts:
- Service Trait - Asynchronous request processing
- Layer Trait - Middleware factory pattern
- ServiceBuilder - Ergonomic middleware composition
- Timeout - Request timeout handling
- RateLimit - Request rate limiting
- LoadShed - Backpressure management
- Buffer - Request buffering
Routing
Basic Routing
Routes map HTTP methods and paths to handlers:
use axum::{
Router,
routing::{get, post, put, delete, patch},
};
let app = Router::new()
.route("/", get(root))
.route("/users", get(list_users).post(create_user))
.route("/users/:id", get(get_user).put(update_user).delete(delete_user))
.route("/posts/:id/comments", get(get_comments).post(add_comment));
Path Parameters
Extract dynamic segments from paths:
use axum::extract::Path;
use serde::Deserialize;
// Single parameter
async fn get_user(Path(user_id): Path<u32>) -> String {
format!("User {}", user_id)
}
// Multiple parameters
#[derive(Deserialize)]
struct PostPath {
user_id: u32,
post_id: u32,
}
async fn get_post(Path(params): Path<PostPath>) -> String {
format!("User {} Post {}", params.user_id, params.post_id)
}
// Using tuple for multiple params
async fn get_comment(
Path((post_id, comment_id)): Path<(u32, u32)>
) -> String {
format!("Post {} Comment {}", post_id, comment_id)
}
Wildcard Routes
Capture remaining path segments:
// Captures all remaining path
async fn handler(Path(path): Path<String>) -> String {
format!("Captured path: {}", path)
}
let app = Router::new()
.route("/{*key}", get(handler));
// GET /foo/bar/baz -> path = "foo/bar/baz"
Important: Nested routers strip matched prefixes, but wildcard routes retain the full URI.
Nested Routers
Organize routes into modules using router nesting:
use axum::{Router, routing::get};
fn api_routes() -> Router {
Router::new()
.route("/users", get(list_users))
.route("/users/:id", get(get_user))
.route("/posts", get(list_posts))
}
fn admin_routes() -> Router {
Router::new()
.route("/dashboard", get(dashboard))
.route("/settings", get(settings))
}
let app = Router::new()
.nest("/api", api_routes())
.nest("/admin", admin_routes())
.route("/", get(root));
Nesting Behavior:
- Matched prefix is stripped from URI before passing to nested router
- Handlers in nested routers only see path relative to nest point
- Fallback handlers are inherited from parent if not defined in child
- Middleware can be applied before or after nesting
Fallback Handlers
Handle unmatched routes:
use axum::{http::StatusCode, handler::Handler};
async fn fallback() -> (StatusCode, &'static str) {
(StatusCode::NOT_FOUND, "Not Found")
}
let app = Router::new()
.route("/", get(handler))
.fallback(fallback);
Fallback Inheritance:
async fn api_fallback() -> (StatusCode, &'static str) {
(StatusCode::NOT_FOUND, "API endpoint not found")
}
let api = Router::new()
.route("/users", get(list_users))
.fallback(api_fallback);
let app = Router::new()
.nest("/api", api)
.fallback(fallback); // Used for non-/api routes
Method Routing
Handle multiple HTTP methods on the same route:
use axum::routing::{get, post, MethodRouter};
// Multiple methods on one route
let app = Router::new()
.route("/users", get(list_users).post(create_user));
// Different handlers per method
let app = Router::new()
.route("/resource",
get(get_resource)
.post(create_resource)
.put(update_resource)
.delete(delete_resource)
.patch(patch_resource)
);
Extractors Deep Dive
Path Extractor
Extract typed path parameters:
use axum::extract::Path;
use serde::Deserialize;
// Simple extraction
async fn user_by_id(Path(id): Path<u32>) -> String {
format!("User {}", id)
}
// Complex extraction
#[derive(Deserialize)]
struct Params {
org: String,
repo: String,
issue: u32,
}
async fn github_issue(Path(params): Path<Params>) -> String {
format!("{}/{} issue #{}", params.org, params.repo, params.issue)
}
let app = Router::new()
.route("/users/:id", get(user_by_id))
.route("/repos/:org/:repo/issues/:issue", get(github_issue));
Query Extractor
Extract query string parameters:
use axum::extract::Query;
use serde::Deserialize;
#[derive(Deserialize)]
struct Pagination {
page: Option<u32>,
per_page: Option<u32>,
}
async fn list_users(Query(pagination): Query<Pagination>) -> String {
let page = pagination.page.unwrap_or(1);
let per_page = pagination.per_page.unwrap_or(20);
format!("Page {} with {} items", page, per_page)
}
// GET /users?page=2&per_page=50
Json Extractor
Parse JSON request bodies:
use axum::extract::Json;
use serde::{Deserialize, Serialize};
#[derive(Deserialize)]
struct CreateUser {
username: String,
email: String,
}
#[derive(Serialize)]
struct User {
id: u32,
username: String,
email: String,
}
async fn create_user(Json(payload): Json<CreateUser>) -> Json<User> {
let user = User {
id: 123,
username: payload.username,
email: payload.email,
};
Json(user)
}
JSON Error Handling:
use axum::extract::rejection::JsonRejection;
use axum::http::StatusCode;
async fn create_user(
payload: Result<Json<CreateUser>, JsonRejection>
) -> Result<Json<User>, (StatusCode, String)> {
match payload {
Ok(Json(create_user)) => {
// Valid JSON
Ok(Json(User { /* ... */ }))
}
Err(JsonRejection::MissingJsonContentType(_)) => {
Err((
StatusCode::BAD_REQUEST,
"Missing `Content-Type: application/json`".to_string(),
))
}
Err(JsonRejection::JsonDataError(err)) => {
Err((
StatusCode::BAD_REQUEST,
format!("Invalid JSON: {}", err),
))
}
Err(JsonRejection::JsonSyntaxError(err)) => {
Err((
StatusCode::BAD_REQUEST,
format!("JSON syntax error: {}", err),
))
}
Err(_) => {
Err((
StatusCode::INTERNAL_SERVER_ERROR,
"Unknown error".to_string(),
))
}
}
}
State Extractor
Access shared application state:
use axum::extract::State;
use std::sync::Arc;
#[derive(Clone)]
struct AppState {
db_pool: Arc<DatabasePool>,
api_key: String,
}
async fn handler(State(state): State<AppState>) -> String {
format!("API Key: {}", state.api_key)
}
let state = AppState {
db_pool: Arc::new(DatabasePool::new()),
api_key: "secret".to_string(),
};
let app = Router::new()
.route("/", get(handler))
.with_state(state);
Extension Extractor
Access request extensions (useful for middleware):
use axum::extract::Extension;
#[derive(Clone)]
struct CurrentUser {
id: u32,
username: String,
}
async fn handler(Extension(user): Extension<CurrentUser>) -> String {
format!("Hello, {}", user.username)
}
// Set by middleware:
async fn auth_middleware(
mut req: Request,
next: Next,
) -> Result<Response, StatusCode> {
let user = CurrentUser {
id: 1,
username: "alice".to_string(),
};
req.extensions_mut().insert(user);
Ok(next.run(req).await)
}
Form Extractor
Parse form-encoded request bodies:
use axum::extract::Form;
use serde::Deserialize;
#[derive(Deserialize)]
struct LoginForm {
username: String,
password: String,
}
async fn login(Form(form): Form<LoginForm>) -> String {
format!("Logging in user: {}", form.username)
}
Headers Extractor
Access request headers:
use axum::http::HeaderMap;
async fn handler(headers: HeaderMap) -> String {
let user_agent = headers
.get("user-agent")
.and_then(|v| v.to_str().ok())
.unwrap_or("unknown");
format!("User-Agent: {}", user_agent)
}
Custom Extractors
Create custom extractors by implementing FromRequest or FromRequestParts:
use axum::{
extract::{FromRequest, Request},
response::{IntoResponse, Response},
http::StatusCode,
async_trait,
};
struct AuthenticatedUser {
id: u32,
username: String,
}
#[async_trait]
impl<S> FromRequestParts<S> for AuthenticatedUser
where
S: Send + Sync,
{
type Rejection = Response;
async fn from_request_parts(
parts: &mut Parts,
state: &S,
) -> Result<Self, Self::Rejection> {
// Extract and validate auth token
let auth_header = parts
.headers
.get("authorization")
.and_then(|v| v.to_str().ok())
.ok_or_else(|| {
(StatusCode::UNAUTHORIZED, "Missing authorization header")
.into_response()
})?;
// Validate token and return user
Ok(AuthenticatedUser {
id: 1,
username: "alice".to_string(),
})
}
}
async fn protected_route(user: AuthenticatedUser) -> String {
format!("Hello, {}", user.username)
}
Middleware
Applying Middleware
Three Ways to Apply Middleware:
- Router-level - Affects all routes
- Route-level - Affects specific routes
- Method-level - Affects specific methods on a route
use axum::{Router, routing::get, middleware};
use tower_http::trace::TraceLayer;
// 1. Router-level
let app = Router::new()
.route("/", get(handler))
.layer(TraceLayer::new_for_http());
// 2. Route-level
let app = Router::new()
.route("/protected", get(handler))
.route_layer(middleware::from_fn(auth_middleware));
// 3. Method-level
let app = Router::new()
.route("/resource",
get(handler)
.route_layer(middleware::from_fn(read_only_auth))
.post(create_handler)
.route_layer(middleware::from_fn(write_auth))
);
Middleware Execution Order
With sequential .layer() calls (bottom-to-top):
let app = Router::new()
.route("/", get(handler))
.layer(layer_three) // Executes third
.layer(layer_two) // Executes second
.layer(layer_one); // Executes first
With ServiceBuilder (top-to-bottom):
use tower::ServiceBuilder;
let app = Router::new()
.route("/", get(handler))
.layer(
ServiceBuilder::new()
.layer(layer_one) // Executes first
.layer(layer_two) // Executes second
.layer(layer_three) // Executes third
);
Common Tower Middleware
TraceLayer - HTTP request tracing:
use tower_http::trace::TraceLayer;
let app = Router::new()
.route("/", get(handler))
.layer(TraceLayer::new_for_http());
CompressionLayer - Response compression:
use tower_http::compression::CompressionLayer;
let app = Router::new()
.route("/", get(handler))
.layer(CompressionLayer::new());
CorsLayer - CORS handling:
use tower_http::cors::{CorsLayer, Any};
let cors = CorsLayer::new()
.allow_origin(Any)
.allow_methods(Any)
.allow_headers(Any);
let app = Router::new()
.route("/api/data", get(handler))
.layer(cors);
TimeoutLayer - Request timeouts:
use tower::timeout::TimeoutLayer;
use std::time::Duration;
let app = Router::new()
.route("/", get(handler))
.layer(TimeoutLayer::new(Duration::from_secs(30)));
HandleErrorLayer
Convert middleware errors to HTTP responses:
use axum::{
error_handling::HandleErrorLayer,
http::{StatusCode, Method, Uri},
BoxError,
};
use tower::ServiceBuilder;
use std::time::Duration;
async fn handle_timeout_error(
method: Method,
uri: Uri,
err: BoxError,
) -> (StatusCode, String) {
if err.is::<tower::timeout::error::Elapsed>() {
(
StatusCode::REQUEST_TIMEOUT,
format!("`{} {}` request timed out", method, uri),
)
} else {
(
StatusCode::INTERNAL_SERVER_ERROR,
format!("`{} {}` failed with {}", method, uri, err),
)
}
}
let app = Router::new()
.route("/", get(handler))
.layer(
ServiceBuilder::new()
.layer(HandleErrorLayer::new(handle_timeout_error))
.layer(TimeoutLayer::new(Duration::from_secs(30)))
);
Custom Middleware with from_fn
Create custom middleware using async functions:
use axum::{
middleware::{self, Next},
extract::Request,
response::Response,
http::StatusCode,
};
async fn auth_middleware(
req: Request,
next: Next,
) -> Result<Response, StatusCode> {
let auth_header = req.headers()
.get("authorization")
.and_then(|h| h.to_str().ok());
if let Some(auth_header) = auth_header {
if validate_token(auth_header).await {
Ok(next.run(req).await)
} else {
Err(StatusCode::UNAUTHORIZED)
}
} else {
Err(StatusCode::UNAUTHORIZED)
}
}
let app = Router::new()
.route("/protected", get(handler))
.layer(middleware::from_fn(auth_middleware));
Passing data from middleware to handler:
use axum::extract::Extension;
#[derive(Clone)]
struct CurrentUser {
id: u32,
username: String,
}
async fn auth_middleware(
mut req: Request,
next: Next,
) -> Result<Response, StatusCode> {
let auth_header = req.headers()
.get("authorization")
.and_then(|h| h.to_str().ok())
.ok_or(StatusCode::UNAUTHORIZED)?;
if let Some(user) = authorize_user(auth_header).await {
req.extensions_mut().insert(user);
Ok(next.run(req).await)
} else {
Err(StatusCode::UNAUTHORIZED)
}
}
async fn handler(Extension(user): Extension<CurrentUser>) -> String {
format!("Hello, {}", user.username)
}
let app = Router::new()
.route("/", get(handler))
.layer(middleware::from_fn(auth_middleware));
Custom Tower Middleware
Implement Tower's Service and Layer traits for full control:
use tower::{Service, Layer};
use axum::{response::Response, extract::Request};
use std::task::{Context, Poll};
use futures_core::future::BoxFuture;
#[derive(Clone)]
struct MyLayer;
impl<S> Layer<S> for MyLayer {
type Service = MyMiddleware<S>;
fn layer(&self, inner: S) -> Self::Service {
MyMiddleware { inner }
}
}
#[derive(Clone)]
struct MyMiddleware<S> {
inner: S,
}
impl<S> Service<Request> for MyMiddleware<S>
where
S: Service<Request, Response = Response> + Send + 'static,
S::Future: Send + 'static,
{
type Response = S::Response;
type Error = S::Error;
type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, request: Request) -> Self::Future {
// Process request
let future = self.inner.call(request);
Box::pin(async move {
let response: Response = future.await?;
// Process response
Ok(response)
})
}
}
let app = Router::new()
.route("/", get(handler))
.layer(MyLayer);
Middleware with State Access
Create middleware that accesses application state:
use axum::extract::State;
use std::sync::Arc;
#[derive(Clone)]
struct AppState {
db: Arc<Database>,
}
#[derive(Clone)]
struct MyLayer {
state: AppState,
}
impl<S> Layer<S> for MyLayer {
type Service = MyService<S>;
fn layer(&self, inner: S) -> Self::Service {
MyService {
inner,
state: self.state.clone(),
}
}
}
#[derive(Clone)]
struct MyService<S> {
inner: S,
state: AppState,
}
impl<S> Service<Request> for MyService<S>
where
S: Service<Request>,
{
type Response = S::Response;
type Error = S::Error;
type Future = S::Future;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, req: Request) -> Self::Future {
// Use self.state here
self.inner.call(req)
}
}
let state = AppState {
db: Arc::new(Database::new()),
};
let app = Router::new()
.route("/", get(handler))
.layer(MyLayer { state: state.clone() })
.with_state(state);
Middleware Before Routing
Apply middleware before routing (e.g., for URI rewriting):
use tower::Layer;
use axum::ServiceExt;
fn rewrite_request_uri(req: Request) -> Request {
// Modify request URI
req
}
let middleware = tower::util::MapRequestLayer::new(rewrite_request_uri);
let app = Router::new()
.route("/", get(handler));
// Apply layer around entire router
let app_with_middleware = middleware.layer(app);
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await?;
axum::serve(listener, app_with_middleware.into_make_service()).await?;
State Management
Basic State
Simple state with cloneable types:
use axum::extract::State;
#[derive(Clone)]
struct AppState {
config: Config,
api_key: String,
}
async fn handler(State(state): State<AppState>) -> String {
format!("Config: {:?}, Key: {}", state.config, state.api_key)
}
let state = AppState {
config: Config::default(),
api_key: "secret".to_string(),
};
let app = Router::new()
.route("/", get(handler))
.with_state(state);
Shared State with Arc
Use Arc for shared ownership of expensive-to-clone types:
use std::sync::Arc;
use tokio::sync::RwLock;
#[derive(Clone)]
struct AppState {
db_pool: Arc<DatabasePool>,
cache: Arc<RwLock<HashMap<String, String>>>,
config: Config, // Cheap to clone
}
async fn handler(State(state): State<AppState>) -> Result<String, StatusCode> {
// Access database pool
let conn = state.db_pool.get().await.map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
// Access cache (read)
let cache = state.cache.read().await;
let value = cache.get("key");
// Access cache (write)
drop(cache); // Release read lock
let mut cache = state.cache.write().await;
cache.insert("new_key".to_string(), "value".to_string());
Ok("Success".to_string())
}
Multiple State Types
Use different state types for different router sections:
#[derive(Clone)]
struct ApiState {
api_key: String,
}
#[derive(Clone)]
struct AppState {
db: Arc<Database>,
}
fn api_routes() -> Router<ApiState> {
Router::new()
.route("/data", get(|State(state): State<ApiState>| async move {
format!("API Key: {}", state.api_key)
}))
}
fn app_routes() -> Router<AppState> {
Router::new()
.route("/users", get(|State(state): State<AppState>| async move {
"Users".to_string()
}))
}
let api_state = ApiState { api_key: "secret".to_string() };
let app_state = AppState { db: Arc::new(Database::new()) };
let app = Router::new()
.nest("/api", api_routes().with_state(api_state))
.nest("/app", app_routes().with_state(app_state));
Generic State in Functions
Return routers with generic state for flexibility:
fn routes<S>() -> Router<S>
where
S: Clone + Send + Sync + 'static,
{
Router::new()
.route("/health", get(|| async { "OK" }))
.route("/version", get(|| async { "1.0.0" }))
}
// Can be combined with any state type
let app = Router::new()
.merge(routes())
.route("/", get(handler))
.with_state(AppState { /* ... */ });
State Transitions
Chain routers with different state requirements:
#[derive(Clone)]
struct StateA {
data_a: String,
}
#[derive(Clone)]
struct StateB {
data_b: String,
}
let router_a: Router<StateA> = Router::new()
.route("/a", get(|State(s): State<StateA>| async move { s.data_a }));
// Provide StateA, next missing state is StateB
let router_b: Router<StateB> = router_a.with_state(StateA {
data_a: "A".to_string(),
});
// Add routes needing StateB
let router_b = router_b
.route("/b", get(|State(s): State<StateB>| async move { s.data_b }));
// Provide StateB, now we have Router<()>
let app: Router<()> = router_b.with_state(StateB {
data_b: "B".to_string(),
});
Error Handling
Basic Error Handling with Result
Use Result to handle errors in handlers:
use axum::http::StatusCode;
async fn handler() -> Result<String, StatusCode> {
let result = some_operation().await;
match result {
Ok(data) => Ok(format!("Success: {}", data)),
Err(_) => Err(StatusCode::INTERNAL_SERVER_ERROR),
}
}
Custom Error Types
Implement IntoResponse for custom errors:
use axum::{
response::{IntoResponse, Response},
http::StatusCode,
Json,
};
use serde::Serialize;
#[derive(Debug)]
enum AppError {
Database(sqlx::Error),
NotFound,
Unauthorized,
ValidationError(String),
}
#[derive(Serialize)]
struct ErrorResponse {
error: String,
message: String,
}
impl IntoResponse for AppError {
fn into_response(self) -> Response {
let (status, error_message) = match self {
AppError::Database(e) => {
tracing::error!("Database error: {}", e);
(StatusCode::INTERNAL_SERVER_ERROR, "Database error")
}
AppError::NotFound => (StatusCode::NOT_FOUND, "Resource not found"),
AppError::Unauthorized => (StatusCode::UNAUTHORIZED, "Unauthorized"),
AppError::ValidationError(msg) => (StatusCode::BAD_REQUEST, &msg),
};
let body = Json(ErrorResponse {
error: status.to_string(),
message: error_message.to_string(),
});
(status, body).into_response()
}
}
// Use in handler
async fn get_user(Path(id): Path<u32>) -> Result<Json<User>, AppError> {
let user = db.get_user(id).await.map_err(AppError::Database)?;
user.ok_or(AppError::NotFound).map(Json)
}
Extractor Rejection Handling
Handle extractor rejections for better error messages:
use axum::extract::rejection::JsonRejection;
async fn create_user(
payload: Result<Json<CreateUser>, JsonRejection>,
) -> Result<Json<User>, AppError> {
let Json(create_user) = payload.map_err(|err| match err {
JsonRejection::MissingJsonContentType(_) => {
AppError::ValidationError("Content-Type must be application/json".to_string())
}
JsonRejection::JsonDataError(e) => {
AppError::ValidationError(format!("Invalid JSON: {}", e))
}
JsonRejection::JsonSyntaxError(e) => {
AppError::ValidationError(format!("JSON syntax error: {}", e))
}
_ => AppError::ValidationError("Invalid request body".to_string()),
})?;
// Process create_user
Ok(Json(user))
}
Custom Extractors with Error Handling
Create extractors with custom rejection types:
use axum::{
extract::{FromRequest, Request},
response::{IntoResponse, Response},
async_trait,
};
struct ValidatedJson<T>(T);
#[async_trait]
impl<S, T> FromRequest<S> for ValidatedJson<T>
where
T: serde::de::DeserializeOwned + Validate,
S: Send + Sync,
{
type Rejection = Response;
async fn from_request(req: Request, state: &S) -> Result<Self, Self::Rejection> {
let Json(data) = Json::<T>::from_request(req, state)
.await
.map_err(|err| {
(
StatusCode::BAD_REQUEST,
format!("Invalid JSON: {}", err),
).into_response()
})?;
data.validate().map_err(|err| {
(
StatusCode::BAD_REQUEST,
format!("Validation error: {}", err),
).into_response()
})?;
Ok(ValidatedJson(data))
}
}
async fn handler(ValidatedJson(data): ValidatedJson<MyData>) -> String {
// data is validated
format!("Received: {:?}", data)
}
Middleware Error Handling
Handle errors from fallible middleware:
use axum::error_handling::HandleErrorLayer;
use tower::ServiceBuilder;
async fn handle_timeout_error(err: BoxError) -> (StatusCode, String) {
if err.is::<tower::timeout::error::Elapsed>() {
(
StatusCode::REQUEST_TIMEOUT,
"Request took too long".to_string(),
)
} else {
(
StatusCode::INTERNAL_SERVER_ERROR,
format!("Unhandled error: {}", err),
)
}
}
let app = Router::new()
.route("/", get(handler))
.layer(
ServiceBuilder::new()
.layer(HandleErrorLayer::new(handle_timeout_error))
.layer(TimeoutLayer::new(Duration::from_secs(30)))
);
Fallible Services
Route to services that can fail:
use axum::error_handling::HandleError;
async fn fallible_operation() -> Result<(), anyhow::Error> {
// Operation that might fail
Ok(())
}
let fallible_service = tower::service_fn(|_req| async {
fallible_operation().await?;
Ok::<_, anyhow::Error>(Response::new(Body::empty()))
});
async fn handle_error(err: anyhow::Error) -> (StatusCode, String) {
(
StatusCode::INTERNAL_SERVER_ERROR,
format!("Something went wrong: {}", err),
)
}
let app = Router::new().route_service(
"/",
HandleError::new(fallible_service, handle_error),
);
Response Building
JSON Responses
Return JSON with type safety:
use axum::Json;
use serde::Serialize;
#[derive(Serialize)]
struct ApiResponse {
success: bool,
data: String,
}
async fn handler() -> Json<ApiResponse> {
Json(ApiResponse {
success: true,
data: "Hello".to_string(),
})
}
HTML Responses
Serve HTML content:
use axum::response::Html;
async fn handler() -> Html<&'static str> {
Html("<h1>Hello, World!</h1>")
}
async fn dynamic_html(Path(name): Path<String>) -> Html<String> {
Html(format!("<h1>Hello, {}</h1>", name))
}
Status Code Responses
Return different status codes:
use axum::http::StatusCode;
async fn handler() -> StatusCode {
StatusCode::NO_CONTENT
}
async fn with_body() -> (StatusCode, String) {
(StatusCode::CREATED, "Resource created".to_string())
}
async fn json_with_status() -> (StatusCode, Json<ApiResponse>) {
(StatusCode::CREATED, Json(ApiResponse { /* ... */ }))
}
Custom Headers
Add custom headers to responses:
use axum::http::{HeaderMap, header};
async fn handler() -> (HeaderMap, String) {
let mut headers = HeaderMap::new();
headers.insert(header::CACHE_CONTROL, "max-age=3600".parse().unwrap());
headers.insert("X-Custom-Header", "value".parse().unwrap());
(headers, "Response body".to_string())
}
Full Response Control
Build complete responses:
use axum::{
response::Response,
http::{StatusCode, header},
body::Body,
};
async fn handler() -> Response {
Response::builder()
.status(StatusCode::OK)
.header(header::CONTENT_TYPE, "application/json")
.header("X-Custom", "value")
.body(Body::from(r#"{"status":"ok"}"#))
.unwrap()
}
Streaming Responses
Stream data to clients:
use axum::response::sse::{Event, Sse};
use futures::stream::{self, Stream};
use std::convert::Infallible;
async fn sse_handler() -> Sse<impl Stream<Item = Result<Event, Infallible>>> {
let stream = stream::iter(0..10).map(|i| {
Ok(Event::default().data(format!("Event {}", i)))
});
Sse::new(stream)
}
File Downloads
Serve files for download:
use axum::{
response::{Response, IntoResponse},
http::{header, StatusCode},
body::Body,
};
use tokio::fs::File;
async fn download_file() -> Result<Response, StatusCode> {
let file = File::open("path/to/file.pdf")
.await
.map_err(|_| StatusCode::NOT_FOUND)?;
let body = Body::from_stream(tokio_util::io::ReaderStream::new(file));
Ok(Response::builder()
.status(StatusCode::OK)
.header(header::CONTENT_TYPE, "application/pdf")
.header(
header::CONTENT_DISPOSITION,
"attachment; filename=\"file.pdf\"",
)
.body(body)
.unwrap())
}
Production Patterns
Database Integration
Integrate with database pools:
use sqlx::{PgPool, postgres::PgPoolOptions};
use std::sync::Arc;
#[derive(Clone)]
struct AppState {
db: PgPool,
}
async fn get_user(
State(state): State<AppState>,
Path(id): Path<i64>,
) -> Result<Json<User>, AppError> {
let user = sqlx::query_as!(User, "SELECT * FROM users WHERE id = $1", id)
.fetch_optional(&state.db)
.await
.map_err(AppError::Database)?
.ok_or(AppError::NotFound)?;
Ok(Json(user))
}
#[tokio::main]
async fn main() {
let db = PgPoolOptions::new()
.max_connections(5)
.connect(&env::var("DATABASE_URL").unwrap())
.await
.unwrap();
let state = AppState { db };
let app = Router::new()
.route("/users/:id", get(get_user))
.with_state(state);
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, app).await.unwrap();
}
Configuration Management
Use environment variables and configuration:
use serde::Deserialize;
use config::{Config, ConfigError, Environment};
#[derive(Debug, Deserialize, Clone)]
struct Settings {
database_url: String,
redis_url: String,
jwt_secret: String,
port: u16,
}
impl Settings {
fn new() -> Result<Self, ConfigError> {
Config::builder()
.add_source(Environment::default())
.build()?
.try_deserialize()
}
}
#[derive(Clone)]
struct AppState {
settings: Settings,
db: PgPool,
}
#[tokio::main]
async fn main() {
let settings = Settings::new().expect("Failed to load configuration");
let db = PgPoolOptions::new()
.connect(&settings.database_url)
.await
.expect("Failed to connect to database");
let state = AppState {
settings: settings.clone(),
db,
};
let app = Router::new()
.route("/", get(handler))
.with_state(state);
let addr = format!("0.0.0.0:{}", settings.port);
let listener = tokio::net::TcpListener::bind(addr).await.unwrap();
axum::serve(listener, app).await.unwrap();
}
Structured Logging
Implement comprehensive logging:
use tracing::{info, error, debug, instrument};
use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
#[tokio::main]
async fn main() {
tracing_subscriber::registry()
.with(
tracing_subscriber::EnvFilter::try_from_default_env()
.unwrap_or_else(|_| "info".into()),
)
.with(tracing_subscriber::fmt::layer())
.init();
info!("Starting server");
let app = Router::new()
.route("/", get(handler))
.layer(TraceLayer::new_for_http());
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
info!("Listening on {}", listener.local_addr().unwrap());
axum::serve(listener, app).await.unwrap();
}
#[instrument]
async fn handler(Path(id): Path<u32>) -> Result<String, AppError> {
debug!("Handling request for user {}", id);
match get_user_from_db(id).await {
Ok(user) => {
info!("Successfully retrieved user {}", id);
Ok(format!("User: {}", user))
}
Err(e) => {
error!("Failed to get user {}: {}", id, e);
Err(AppError::Database(e))
}
}
}
Graceful Shutdown
Implement graceful shutdown handling:
use tokio::signal;
async fn shutdown_signal() {
let ctrl_c = async {
signal::ctrl_c()
.await
.expect("failed to install Ctrl+C handler");
};
#[cfg(unix)]
let terminate = async {
signal::unix::signal(signal::unix::SignalKind::terminate())
.expect("failed to install signal handler")
.recv()
.await;
};
#[cfg(not(unix))]
let terminate = std::future::pending::<()>();
tokio::select! {
_ = ctrl_c => {},
_ = terminate => {},
}
println!("Signal received, starting graceful shutdown");
}
#[tokio::main]
async fn main() {
let app = Router::new().route("/", get(handler));
let listener = tokio::net::TcpListener::bind("0.0.0.0:3000").await.unwrap();
axum::serve(listener, app)
.with_graceful_shutdown(shutdown_signal())
.await
.unwrap();
}
Health Checks
Implement health check endpoints:
use serde::Serialize;
#[derive(Serialize)]
struct HealthResponse {
status: String,
database: String,
cache: String,
}
async fn health_check(State(state): State<AppState>) -> Json<HealthResponse> {
let db_status = match sqlx::query("SELECT 1").fetch_one(&state.db).await {
Ok(_) => "healthy",
Err(_) => "unhealthy",
};
let cache_status = match state.redis.ping().await {
Ok(_) => "healthy",
Err(_) => "unhealthy",
};
Json(HealthResponse {
status: if db_status == "healthy" && cache_status == "healthy" {
"healthy".to_string()
} else {
"degraded".to_string()
},
database: db_status.to_string(),
cache: cache_status.to_string(),
})
}
let app = Router::new()
.route("/health", get(health_check))
.route("/ready", get(readiness_check))
.with_state(state);
Rate Limiting
Implement rate limiting:
use tower::limit::RateLimitLayer;
use std::time::Duration;
let app = Router::new()
.route("/api/data", get(handler))
.layer(RateLimitLayer::new(
100, // max requests
Duration::from_secs(60), // per minute
));
Request Validation
Validate requests with custom extractors:
use validator::{Validate, ValidationError};
#[derive(Debug, Deserialize, Validate)]
struct CreateUserRequest {
#[validate(length(min = 3, max = 50))]
username: String,
#[validate(email)]
email: String,
#[validate(length(min = 8))]
password: String,
}
struct ValidatedJson<T>(T);
#[async_trait]
impl<S, T> FromRequest<S> for ValidatedJson<T>
where
T: DeserializeOwned + Validate,
S: Send + Sync,
{
type Rejection = (StatusCode, String);
async fn from_request(req: Request, state: &S) -> Result<Self, Self::Rejection> {
let Json(data) = Json::<T>::from_request(req, state)
.await
.map_err(|e| (StatusCode::BAD_REQUEST, e.to_string()))?;
data.validate()
.map_err(|e| (StatusCode::BAD_REQUEST, e.to_string()))?;
Ok(ValidatedJson(data))
}
}
async fn create_user(
ValidatedJson(user): ValidatedJson<CreateUserRequest>,
) -> Result<Json<User>, AppError> {
// user is validated
Ok(Json(User { /* ... */ }))
}
Testing
Unit Testing Handlers
Test handlers in isolation:
#[cfg(test)]
mod tests {
use super::*;
use axum::body::Body;
use axum::http::{Request, StatusCode};
use tower::ServiceExt;
#[tokio::test]
async fn test_handler() {
let app = Router::new().route("/", get(handler));
let response = app
.oneshot(Request::builder().uri("/").body(Body::empty()).unwrap())
.await
.unwrap();
assert_eq!(response.status(), StatusCode::OK);
}
}
Integration Testing
Test full application:
#[cfg(test)]
mod tests {
use super::*;
use axum::body::Body;
use axum::http::{Request, StatusCode, Method};
use tower::ServiceExt;
use serde_json::json;
#[tokio::test]
async fn test_create_user() {
let state = AppState::test();
let app = create_app(state);
let request_body = json!({
"username": "testuser",
"email": "test@example.com"
});
let response = app
.oneshot(
Request::builder()
.method(Method::POST)
.uri("/users")
.header("content-type", "application/json")
.body(Body::from(request_body.to_string()))
.unwrap()
)
.await
.unwrap();
assert_eq!(response.status(), StatusCode::CREATED);
}
}
Best Practices
Handler Organization
- Keep handlers thin - Move business logic to service layer
- Use extractors - Let type system handle extraction
- Return Result types - Use custom error types
- Instrument handlers - Add tracing for observability
State Management
- Use Arc for expensive types - Database pools, caches
- Keep state minimal - Only what's truly shared
- Implement Clone - Required for State extractor
- Avoid mutation - Use interior mutability (RwLock, Mutex) when needed
Error Handling
- Create custom error types - Implement IntoResponse
- Provide context - Include helpful error messages
- Log errors appropriately - Use tracing
- Return proper status codes - Match HTTP semantics
Middleware
- Use ServiceBuilder - More intuitive ordering
- Apply at right level - Router vs route vs method
- Handle errors - Use HandleErrorLayer for fallible middleware
- Keep middleware focused - Single responsibility
Performance
- Use connection pooling - For databases and external services
- Enable compression - CompressionLayer for responses
- Implement caching - Reduce redundant operations
- Use backpressure - LoadShedLayer, RateLimitLayer
- Optimize serialization - Use efficient JSON libraries
Security
- Validate inputs - Use custom extractors with validation
- Implement authentication - Use middleware for auth
- Use HTTPS - In production environments
- Set security headers - CORS, CSP, etc.
- Rate limit - Prevent abuse
Common Patterns
Repository Pattern
trait UserRepository {
async fn get(&self, id: u32) -> Result<User, AppError>;
async fn create(&self, user: CreateUser) -> Result<User, AppError>;
async fn update(&self, id: u32, user: UpdateUser) -> Result<User, AppError>;
async fn delete(&self, id: u32) -> Result<(), AppError>;
}
struct PostgresUserRepository {
pool: PgPool,
}
impl UserRepository for PostgresUserRepository {
async fn get(&self, id: u32) -> Result<User, AppError> {
// Implementation
}
}
#[derive(Clone)]
struct AppState {
user_repo: Arc<dyn UserRepository + Send + Sync>,
}
async fn get_user(
State(state): State<AppState>,
Path(id): Path<u32>,
) -> Result<Json<User>, AppError> {
let user = state.user_repo.get(id).await?;
Ok(Json(user))
}
Service Layer Pattern
struct UserService {
repo: Arc<dyn UserRepository + Send + Sync>,
email_service: Arc<EmailService>,
}
impl UserService {
async fn create_user(&self, data: CreateUser) -> Result<User, AppError> {
let user = self.repo.create(data).await?;
self.email_service.send_welcome_email(&user).await?;
Ok(user)
}
}
#[derive(Clone)]
struct AppState {
user_service: Arc<UserService>,
}
Versioned APIs
fn v1_routes() -> Router<AppState> {
Router::new()
.route("/users", get(v1::list_users))
.route("/users/:id", get(v1::get_user))
}
fn v2_routes() -> Router<AppState> {
Router::new()
.route("/users", get(v2::list_users))
.route("/users/:id", get(v2::get_user))
}
let app = Router::new()
.nest("/api/v1", v1_routes())
.nest("/api/v2", v2_routes())
.with_state(state);
Skill Version: 1.0.0 Last Updated: October 2025 Skill Category: Web Development, REST APIs, Rust, Async Programming Compatible With: Axum 0.7+, Tokio 1.0+, Tower 0.4+
FAQ
What does the axum-web-framework skill do?
Complete guide for Axum web framework including routing, extractors, middleware, state management, error handling, and production deployment
How do I install axum-web-framework?
Run npx skills add https://github.com/manutej/luxor-claude-marketplace --skill axum-web-framework in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/axum-web-framework/ (personal) or .claude/skills/axum-web-framework/ (project).
Which AI agents can use axum-web-framework?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is axum-web-framework safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains axum-web-framework?
It is published by manutej in manutej/luxor-claude-marketplace. It has 651 recorded installs.
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azure-deploy
microsoft/azure-skills
Execute Azure deployments for ALREADY-PREPARED applications that have existing .azure/deployment-plan.md and infrastructure files. DO NOT use this skill when the user asks to CREATE a new application — use azure-prepare instead. This skill runs azd up, azd deploy, terraform apply, and az deployment commands with built-in error recovery. Requires .azure/deployment-plan.md from azure-prepare and validated status from azure-validate. WHEN: "run azd up", "run azd deploy", "execute deployment", "push to production", "push to cloud", "go live", "ship it", "bicep deploy", "terraform apply", "publish to Azure", "launch on Azure". DO NOT USE WHEN: "create and deploy", "build and deploy", "create a new app", "set up infrastructure", "create and deploy to Azure using Terraform" — use azure-prepare for these.
azure-validate
microsoft/azure-skills
Pre-deployment validation for Azure readiness. Run deep checks on configuration, infrastructure (Bicep or Terraform), RBAC role assignments, managed identity permissions, and prerequisites before deploying. WHEN: validate my app, check deployment readiness, run preflight checks, verify configuration, check if ready to deploy, validate azure.yaml, validate Bicep, test before deploying, troubleshoot deployment errors, validate Azure Functions, validate function app, validate serverless deployment, verify RBAC roles, check role assignments, review managed identity permissions, what-if analysis, validate Container Apps deployment.