Struct AppBuilder 

pub struct AppBuilder { /* private fields */ }

Builder for constructing an App.

Use this to configure routes, middleware, and shared state before building the final application.

Example

let app = App::builder()
    .config(AppConfig::new().name("My API"))
    .state(DatabasePool::new())
    .middleware(LoggingMiddleware::new())
    .on_startup(|| {
        println!("Server starting...");
        Ok(())
    })
    .on_shutdown(|| {
        println!("Server stopping...");
    })
    .route("/", Method::Get, index_handler)
    .route("/items", Method::Get, list_items)
    .route("/items", Method::Post, create_item)
    .route("/items/{id}", Method::Get, get_item)
    .build();

Implementations

impl AppBuilder

pub fn new() -> AppBuilder

Creates a new application builder.

pub fn config(self, config: AppConfig) -> AppBuilder

Sets the application configuration.

Examples found in repository

examples/getting_started.rs (line 102)

fn main() {
    println!("Getting Started Guide - Code Validation\n");

    // === Basic App Example ===
    println!("1. Basic app with two routes:");
    let app = App::builder()
        .get("/", hello)
        .get("/health", health)
        .build();

    println!("   Routes: {}", app.route_count());
    let client = TestClient::new(app);

    let response = client.get("/").send();
    println!(
        "   GET / -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(response.status().as_u16(), 200, "GET / should return 200") {
        return;
    }
    if !check_eq(response.text(), "Hello, World!", "GET / should return body") {
        return;
    }

    let response = client.get("/health").send();
    println!(
        "   GET /health -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /health should return 200",
    ) {
        return;
    }

    // === App with Middleware ===
    println!("\n2. App with middleware:");
    let app = App::builder()
        .middleware(RequestIdMiddleware::new())
        .middleware(SecurityHeaders::new())
        .get("/", hello)
        .build();

    let client = TestClient::new(app);
    let response = client.get("/").send();
    println!("   GET / -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET / with middleware should return 200",
    ) {
        return;
    }

    // === App with Configuration ===
    println!("\n3. App with configuration:");
    let config = AppConfig::new()
        .name("My API")
        .version("1.0.0")
        .debug(true)
        .max_body_size(10 * 1024 * 1024)
        .request_timeout_ms(30_000);

    let app = App::builder().config(config).get("/", hello).build();

    println!("   App name: {}", app.config().name);
    println!("   Version: {}", app.config().version);
    if !check_eq(
        app.config().name.as_str(),
        "My API",
        "Config name should match",
    ) {
        return;
    }
    if !check_eq(
        app.config().version.as_str(),
        "1.0.0",
        "Config version should match",
    ) {
        return;
    }

    // === 404 for unknown routes ===
    println!("\n4. 404 for unknown routes:");
    let app = App::builder().get("/", hello).build();

    let client = TestClient::new(app);
    let response = client.get("/nonexistent").send();
    println!("   GET /nonexistent -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        404,
        "Unknown routes should return 404",
    ) {
        return;
    }

    println!("\nAll getting started examples validated successfully!");
}

pub fn openapi(self, config: OpenApiConfig) -> AppBuilder

Enables and configures OpenAPI documentation.

When enabled, the application will automatically generate an OpenAPI 3.1 specification and serve it at the configured endpoint.

Example

let app = App::builder()
    .openapi(OpenApiConfig::new()
        .title("My API")
        .version("1.0.0")
        .description("A sample API"))
    .build();

pub fn enable_docs(self, config: DocsConfig) -> AppBuilder

Enables and configures interactive API documentation endpoints.

This wires crate::docs::DocsConfig into the application build and ensures an OpenAPI JSON endpoint is served at config.openapi_path unless overridden later.

Notes:

• Docs endpoints are appended during build() so they don’t appear in the OpenAPI spec.
• If OpenAPI is already configured, its openapi_path is updated to match DocsConfig.

pub fn route<H, Fut>( self, path: impl Into<String>, method: Method, handler: H, ) -> AppBuilder

where H: Fn(&RequestContext, &mut Request) -> Fut + Send + Sync + 'static, Fut: Future<Output = Response> + Send + 'static,

Adds a route to the application.

Routes are matched in the order they are added.

pub fn route_entry(self, entry: RouteEntry) -> AppBuilder

Adds a pre-built RouteEntry to the application.

This is primarily used by proc-macro generated route builders that already know the method/path and can build an extraction wrapper.

pub fn websocket<H, Fut>( self, path: impl Into<String>, handler: H, ) -> AppBuilder

where H: Fn(&RequestContext, &mut Request, WebSocket) -> Fut + Send + Sync + 'static, Fut: Future<Output = Result<(), WebSocketError>> + Send + 'static,

Adds a websocket route to the application.

WebSocket routes are matched only when the server receives a valid websocket upgrade request. They do not appear in OpenAPI output.

pub fn get<H, Fut>(self, path: impl Into<String>, handler: H) -> AppBuilder

where H: Fn(&RequestContext, &mut Request) -> Fut + Send + Sync + 'static, Fut: Future<Output = Response> + Send + 'static,

Adds a GET route.

Examples found in repository

examples/hello_world.rs (line 80)

fn main() {
    println!("fastapi_rust Hello World Example");
    println!("================================\n");

    // Build the application
    //
    // App::builder() creates a new application builder that lets you:
    // - Add routes for different HTTP methods
    // - Configure middleware
    // - Set application state
    // - Define exception handlers
    let app = App::builder()
        // Register a GET handler for the root path "/"
        //
        // This is equivalent to:
        //   @app.get("/")
        //   def hello():
        //       return "Hello, World!"
        // in Python FastAPI
        .get("/", hello_handler)
        // Build the final immutable App
        .build();

    println!("App created with {} route(s)\n", app.route_count());

    // Create a test client to make requests to our app
    //
    // TestClient wraps any Handler (including App) and provides
    // a convenient API for making HTTP requests in tests.
    let client = TestClient::new(app);

    // Make a GET request to "/"
    println!("Making request: GET /");
    let response = client.get("/").send();

    // Check the response
    println!(
        "GET / -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    println!("Response: {}\n", response.text());

    // Verify success
    if !check_eq(response.status().as_u16(), 200, "GET / should return 200") {
        return;
    }
    if !check_eq(response.text(), "Hello, World!", "GET / should return body") {
        return;
    }

    // Try a path that doesn't exist - should get 404
    println!("Making request: GET /not-found");
    let response = client.get("/not-found").send();
    println!(
        "GET /not-found -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        404,
        "Unknown routes should return 404",
    ) {
        return;
    }

    println!("\nAll assertions passed!");
}

examples/getting_started.rs (line 40)

fn main() {
    println!("Getting Started Guide - Code Validation\n");

    // === Basic App Example ===
    println!("1. Basic app with two routes:");
    let app = App::builder()
        .get("/", hello)
        .get("/health", health)
        .build();

    println!("   Routes: {}", app.route_count());
    let client = TestClient::new(app);

    let response = client.get("/").send();
    println!(
        "   GET / -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(response.status().as_u16(), 200, "GET / should return 200") {
        return;
    }
    if !check_eq(response.text(), "Hello, World!", "GET / should return body") {
        return;
    }

    let response = client.get("/health").send();
    println!(
        "   GET /health -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /health should return 200",
    ) {
        return;
    }

    // === App with Middleware ===
    println!("\n2. App with middleware:");
    let app = App::builder()
        .middleware(RequestIdMiddleware::new())
        .middleware(SecurityHeaders::new())
        .get("/", hello)
        .build();

    let client = TestClient::new(app);
    let response = client.get("/").send();
    println!("   GET / -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET / with middleware should return 200",
    ) {
        return;
    }

    // === App with Configuration ===
    println!("\n3. App with configuration:");
    let config = AppConfig::new()
        .name("My API")
        .version("1.0.0")
        .debug(true)
        .max_body_size(10 * 1024 * 1024)
        .request_timeout_ms(30_000);

    let app = App::builder().config(config).get("/", hello).build();

    println!("   App name: {}", app.config().name);
    println!("   Version: {}", app.config().version);
    if !check_eq(
        app.config().name.as_str(),
        "My API",
        "Config name should match",
    ) {
        return;
    }
    if !check_eq(
        app.config().version.as_str(),
        "1.0.0",
        "Config version should match",
    ) {
        return;
    }

    // === 404 for unknown routes ===
    println!("\n4. 404 for unknown routes:");
    let app = App::builder().get("/", hello).build();

    let client = TestClient::new(app);
    let response = client.get("/nonexistent").send();
    println!("   GET /nonexistent -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        404,
        "Unknown routes should return 404",
    ) {
        return;
    }

    println!("\nAll getting started examples validated successfully!");
}

examples/crud_api.rs (line 286)

fn main() {
    // Initialize the global store
    let mut guard = STORE
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner);
    *guard = Some(UserDb {
        users: HashMap::new(),
        next_id: 1,
    });

    println!("fastapi_rust CRUD API Example");
    println!("=============================\n");

    let app = App::builder()
        .post("/users", create_user)
        .get("/users", list_users)
        .get("/users/{id}", get_user)
        .put("/users/{id}", update_user)
        .delete("/users/{id}", delete_user)
        .build();

    println!("App created with {} route(s)\n", app.route_count());
    let client = TestClient::new(app);

    // 1. Create users
    println!("1. Create users");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice", "email": "alice@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Bob", "email": "bob@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    // 2. List users
    println!("\n2. List all users");
    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    // 3. Get user by ID
    println!("\n3. Get user by ID");
    let resp = client.get("/users/1").send();
    println!(
        "   GET /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Get user should return 200") {
        return;
    }

    // 4. Get nonexistent user
    println!("\n4. Get nonexistent user");
    let resp = client.get("/users/999").send();
    println!(
        "   GET /users/999 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Missing user should return 404",
    ) {
        return;
    }

    // 5. Update user
    println!("\n5. Update user");
    let resp = client
        .put("/users/1")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice Smith", "email": "alice.smith@example.com"}"#)
        .send();
    println!(
        "   PUT /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Update user should return 200") {
        return;
    }

    // 6. Validation: empty name
    println!("\n6. Validation error (empty name)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "", "email": "bad@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 400, "Empty name should return 400") {
        return;
    }

    // 7. Validation: invalid email
    println!("\n7. Validation error (invalid email)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Charlie", "email": "not-an-email"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        400,
        "Invalid email should return 400",
    ) {
        return;
    }

    // 8. Wrong Content-Type
    println!("\n8. Wrong Content-Type");
    let resp = client
        .post("/users")
        .header("content-type", "text/plain")
        .body(r#"{"name": "Dan", "email": "dan@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        415,
        "Wrong Content-Type should return 415",
    ) {
        return;
    }

    // 9. Delete user
    println!("\n9. Delete user");
    let resp = client.delete("/users/2").send();
    println!("   DELETE /users/2 -> {}", resp.status().as_u16());
    if !check_eq(resp.status().as_u16(), 204, "Delete user should return 204") {
        return;
    }

    // 10. Verify deletion
    println!("\n10. Verify deletion");
    let resp = client.get("/users/2").send();
    println!(
        "   GET /users/2 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Deleted user should return 404",
    ) {
        return;
    }

    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    println!("\nAll CRUD operations passed!");
}

examples/auth_example.rs (line 274)

fn main() {
    println!("fastapi_rust Authentication Example");
    println!("====================================\n");

    // Build the application with public and protected routes
    let app = App::builder()
        // Public endpoints - accessible to everyone
        .get("/public", public_handler)
        // Login endpoint - returns a token
        .post("/login", login_handler)
        // Protected endpoint - requires valid bearer token
        .get("/protected", protected_handler)
        .build();

    println!("App created with {} route(s)\n", app.route_count());

    // Create a test client
    let client = TestClient::new(app);

    // =========================================================================
    // Test 1: Public endpoint - no auth required
    // =========================================================================
    println!("1. Public endpoint - no auth required");
    let response = client.get("/public").send();
    println!(
        "   GET /public -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /public should return 200",
    ) {
        return;
    }
    if !check(
        response.text().contains("public endpoint"),
        "GET /public should include the public endpoint body",
    ) {
        return;
    }

    // =========================================================================
    // Test 2: Protected endpoint - without token (should get 401)
    // =========================================================================
    println!("\n2. Protected endpoint - without token");
    let response = client.get("/protected").send();
    println!(
        "   GET /protected -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        401,
        "Protected endpoint should return 401 without token",
    ) {
        return;
    }

    // Check for WWW-Authenticate header
    let has_www_auth = response
        .headers()
        .iter()
        .any(|(name, value)| name == "www-authenticate" && value == b"Bearer");
    if !check(
        has_www_auth,
        "401 response should include WWW-Authenticate: Bearer header",
    ) {
        return;
    }

    // =========================================================================
    // Test 3: Login endpoint - get a token
    // =========================================================================
    println!("\n3. Login endpoint - get a token");
    let response = client
        .post("/login")
        .header("content-type", "application/json")
        .body(r#"{"username":"test","password":"test123"}"#)
        .send();
    println!(
        "   POST /login -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "POST /login should return 200",
    ) {
        return;
    }

    // Parse the response to get the token
    let body_text = response.text();
    let body: serde_json::Value = match serde_json::from_str(body_text) {
        Ok(body) => body,
        Err(err) => {
            eprintln!("Failed to parse login response JSON: {err}");
            return;
        }
    };
    let Some(bearer_value) = body.get("access_token").and_then(|value| value.as_str()) else {
        eprintln!("Login response missing access_token");
        return;
    };
    println!("   Bearer value: {bearer_value}");
    if !check_eq(
        bearer_value,
        DEMO_BEARER_VALUE,
        "Login should return the expected bearer value",
    ) {
        return;
    }

    // =========================================================================
    // Test 4: Protected endpoint - with valid token (should get 200)
    // =========================================================================
    println!("\n4. Protected endpoint - with valid token");
    let response = client
        .get("/protected")
        .header("authorization", format!("Bearer {DEMO_BEARER_VALUE}"))
        .send();
    println!(
        "   GET /protected (Authorization: Bearer {}) -> {} {}",
        DEMO_BEARER_VALUE,
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "Protected endpoint should return 200 with valid token",
    ) {
        return;
    }
    if !check(
        response.text().contains("protected resource"),
        "Protected endpoint should include protected resource body",
    ) {
        return;
    }

    // =========================================================================
    // Test 5: Protected endpoint - with invalid token (should get 403)
    // =========================================================================
    println!("\n5. Protected endpoint - with invalid token");
    let response = client
        .get("/protected")
        .header("authorization", "Bearer wrong_token")
        .send();
    println!(
        "   GET /protected (Authorization: Bearer wrong_token) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        403,
        "Protected endpoint should return 403 with invalid token",
    ) {
        return;
    }

    // =========================================================================
    // Test 6: Protected endpoint - with wrong auth scheme (should get 401)
    // =========================================================================
    println!("\n6. Protected endpoint - with wrong auth scheme");
    let response = client
        .get("/protected")
        .header("authorization", "Basic dXNlcjpwYXNz")
        .send();
    println!(
        "   GET /protected (Authorization: Basic ...) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        401,
        "Protected endpoint should return 401 with wrong auth scheme",
    ) {
        return;
    }

    // =========================================================================
    // Test 7: Login with wrong Content-Type (should get 415)
    // =========================================================================
    println!("\n7. Login with wrong Content-Type");
    let response = client
        .post("/login")
        .header("content-type", "text/plain")
        .body("demo=true")
        .send();
    println!(
        "   POST /login (Content-Type: text/plain) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        415,
        "Login should return 415 with wrong Content-Type",
    ) {
        return;
    }

    // =========================================================================
    // Test 8: Token case sensitivity (lowercase 'bearer')
    // =========================================================================
    println!("\n8. Token case sensitivity (lowercase 'bearer')");
    let response = client
        .get("/protected")
        .header("authorization", format!("bearer {DEMO_BEARER_VALUE}"))
        .send();
    println!(
        "   GET /protected (Authorization: bearer {}) -> {} {}",
        DEMO_BEARER_VALUE,
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "Bearer scheme should be case-insensitive (lowercase accepted)",
    ) {
        return;
    }

    println!("\nAll authentication tests passed!");
}

pub fn post<H, Fut>(self, path: impl Into<String>, handler: H) -> AppBuilder

where H: Fn(&RequestContext, &mut Request) -> Fut + Send + Sync + 'static, Fut: Future<Output = Response> + Send + 'static,

Adds a POST route.

Examples found in repository

examples/crud_api.rs (line 285)

fn main() {
    // Initialize the global store
    let mut guard = STORE
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner);
    *guard = Some(UserDb {
        users: HashMap::new(),
        next_id: 1,
    });

    println!("fastapi_rust CRUD API Example");
    println!("=============================\n");

    let app = App::builder()
        .post("/users", create_user)
        .get("/users", list_users)
        .get("/users/{id}", get_user)
        .put("/users/{id}", update_user)
        .delete("/users/{id}", delete_user)
        .build();

    println!("App created with {} route(s)\n", app.route_count());
    let client = TestClient::new(app);

    // 1. Create users
    println!("1. Create users");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice", "email": "alice@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Bob", "email": "bob@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    // 2. List users
    println!("\n2. List all users");
    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    // 3. Get user by ID
    println!("\n3. Get user by ID");
    let resp = client.get("/users/1").send();
    println!(
        "   GET /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Get user should return 200") {
        return;
    }

    // 4. Get nonexistent user
    println!("\n4. Get nonexistent user");
    let resp = client.get("/users/999").send();
    println!(
        "   GET /users/999 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Missing user should return 404",
    ) {
        return;
    }

    // 5. Update user
    println!("\n5. Update user");
    let resp = client
        .put("/users/1")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice Smith", "email": "alice.smith@example.com"}"#)
        .send();
    println!(
        "   PUT /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Update user should return 200") {
        return;
    }

    // 6. Validation: empty name
    println!("\n6. Validation error (empty name)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "", "email": "bad@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 400, "Empty name should return 400") {
        return;
    }

    // 7. Validation: invalid email
    println!("\n7. Validation error (invalid email)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Charlie", "email": "not-an-email"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        400,
        "Invalid email should return 400",
    ) {
        return;
    }

    // 8. Wrong Content-Type
    println!("\n8. Wrong Content-Type");
    let resp = client
        .post("/users")
        .header("content-type", "text/plain")
        .body(r#"{"name": "Dan", "email": "dan@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        415,
        "Wrong Content-Type should return 415",
    ) {
        return;
    }

    // 9. Delete user
    println!("\n9. Delete user");
    let resp = client.delete("/users/2").send();
    println!("   DELETE /users/2 -> {}", resp.status().as_u16());
    if !check_eq(resp.status().as_u16(), 204, "Delete user should return 204") {
        return;
    }

    // 10. Verify deletion
    println!("\n10. Verify deletion");
    let resp = client.get("/users/2").send();
    println!(
        "   GET /users/2 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Deleted user should return 404",
    ) {
        return;
    }

    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    println!("\nAll CRUD operations passed!");
}

examples/auth_example.rs (line 276)

fn main() {
    println!("fastapi_rust Authentication Example");
    println!("====================================\n");

    // Build the application with public and protected routes
    let app = App::builder()
        // Public endpoints - accessible to everyone
        .get("/public", public_handler)
        // Login endpoint - returns a token
        .post("/login", login_handler)
        // Protected endpoint - requires valid bearer token
        .get("/protected", protected_handler)
        .build();

    println!("App created with {} route(s)\n", app.route_count());

    // Create a test client
    let client = TestClient::new(app);

    // =========================================================================
    // Test 1: Public endpoint - no auth required
    // =========================================================================
    println!("1. Public endpoint - no auth required");
    let response = client.get("/public").send();
    println!(
        "   GET /public -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /public should return 200",
    ) {
        return;
    }
    if !check(
        response.text().contains("public endpoint"),
        "GET /public should include the public endpoint body",
    ) {
        return;
    }

    // =========================================================================
    // Test 2: Protected endpoint - without token (should get 401)
    // =========================================================================
    println!("\n2. Protected endpoint - without token");
    let response = client.get("/protected").send();
    println!(
        "   GET /protected -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        401,
        "Protected endpoint should return 401 without token",
    ) {
        return;
    }

    // Check for WWW-Authenticate header
    let has_www_auth = response
        .headers()
        .iter()
        .any(|(name, value)| name == "www-authenticate" && value == b"Bearer");
    if !check(
        has_www_auth,
        "401 response should include WWW-Authenticate: Bearer header",
    ) {
        return;
    }

    // =========================================================================
    // Test 3: Login endpoint - get a token
    // =========================================================================
    println!("\n3. Login endpoint - get a token");
    let response = client
        .post("/login")
        .header("content-type", "application/json")
        .body(r#"{"username":"test","password":"test123"}"#)
        .send();
    println!(
        "   POST /login -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "POST /login should return 200",
    ) {
        return;
    }

    // Parse the response to get the token
    let body_text = response.text();
    let body: serde_json::Value = match serde_json::from_str(body_text) {
        Ok(body) => body,
        Err(err) => {
            eprintln!("Failed to parse login response JSON: {err}");
            return;
        }
    };
    let Some(bearer_value) = body.get("access_token").and_then(|value| value.as_str()) else {
        eprintln!("Login response missing access_token");
        return;
    };
    println!("   Bearer value: {bearer_value}");
    if !check_eq(
        bearer_value,
        DEMO_BEARER_VALUE,
        "Login should return the expected bearer value",
    ) {
        return;
    }

    // =========================================================================
    // Test 4: Protected endpoint - with valid token (should get 200)
    // =========================================================================
    println!("\n4. Protected endpoint - with valid token");
    let response = client
        .get("/protected")
        .header("authorization", format!("Bearer {DEMO_BEARER_VALUE}"))
        .send();
    println!(
        "   GET /protected (Authorization: Bearer {}) -> {} {}",
        DEMO_BEARER_VALUE,
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "Protected endpoint should return 200 with valid token",
    ) {
        return;
    }
    if !check(
        response.text().contains("protected resource"),
        "Protected endpoint should include protected resource body",
    ) {
        return;
    }

    // =========================================================================
    // Test 5: Protected endpoint - with invalid token (should get 403)
    // =========================================================================
    println!("\n5. Protected endpoint - with invalid token");
    let response = client
        .get("/protected")
        .header("authorization", "Bearer wrong_token")
        .send();
    println!(
        "   GET /protected (Authorization: Bearer wrong_token) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        403,
        "Protected endpoint should return 403 with invalid token",
    ) {
        return;
    }

    // =========================================================================
    // Test 6: Protected endpoint - with wrong auth scheme (should get 401)
    // =========================================================================
    println!("\n6. Protected endpoint - with wrong auth scheme");
    let response = client
        .get("/protected")
        .header("authorization", "Basic dXNlcjpwYXNz")
        .send();
    println!(
        "   GET /protected (Authorization: Basic ...) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        401,
        "Protected endpoint should return 401 with wrong auth scheme",
    ) {
        return;
    }

    // =========================================================================
    // Test 7: Login with wrong Content-Type (should get 415)
    // =========================================================================
    println!("\n7. Login with wrong Content-Type");
    let response = client
        .post("/login")
        .header("content-type", "text/plain")
        .body("demo=true")
        .send();
    println!(
        "   POST /login (Content-Type: text/plain) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        415,
        "Login should return 415 with wrong Content-Type",
    ) {
        return;
    }

    // =========================================================================
    // Test 8: Token case sensitivity (lowercase 'bearer')
    // =========================================================================
    println!("\n8. Token case sensitivity (lowercase 'bearer')");
    let response = client
        .get("/protected")
        .header("authorization", format!("bearer {DEMO_BEARER_VALUE}"))
        .send();
    println!(
        "   GET /protected (Authorization: bearer {}) -> {} {}",
        DEMO_BEARER_VALUE,
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "Bearer scheme should be case-insensitive (lowercase accepted)",
    ) {
        return;
    }

    println!("\nAll authentication tests passed!");
}

pub fn put<H, Fut>(self, path: impl Into<String>, handler: H) -> AppBuilder

where H: Fn(&RequestContext, &mut Request) -> Fut + Send + Sync + 'static, Fut: Future<Output = Response> + Send + 'static,

Adds a PUT route.

Examples found in repository

examples/crud_api.rs (line 288)

fn main() {
    // Initialize the global store
    let mut guard = STORE
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner);
    *guard = Some(UserDb {
        users: HashMap::new(),
        next_id: 1,
    });

    println!("fastapi_rust CRUD API Example");
    println!("=============================\n");

    let app = App::builder()
        .post("/users", create_user)
        .get("/users", list_users)
        .get("/users/{id}", get_user)
        .put("/users/{id}", update_user)
        .delete("/users/{id}", delete_user)
        .build();

    println!("App created with {} route(s)\n", app.route_count());
    let client = TestClient::new(app);

    // 1. Create users
    println!("1. Create users");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice", "email": "alice@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Bob", "email": "bob@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    // 2. List users
    println!("\n2. List all users");
    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    // 3. Get user by ID
    println!("\n3. Get user by ID");
    let resp = client.get("/users/1").send();
    println!(
        "   GET /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Get user should return 200") {
        return;
    }

    // 4. Get nonexistent user
    println!("\n4. Get nonexistent user");
    let resp = client.get("/users/999").send();
    println!(
        "   GET /users/999 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Missing user should return 404",
    ) {
        return;
    }

    // 5. Update user
    println!("\n5. Update user");
    let resp = client
        .put("/users/1")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice Smith", "email": "alice.smith@example.com"}"#)
        .send();
    println!(
        "   PUT /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Update user should return 200") {
        return;
    }

    // 6. Validation: empty name
    println!("\n6. Validation error (empty name)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "", "email": "bad@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 400, "Empty name should return 400") {
        return;
    }

    // 7. Validation: invalid email
    println!("\n7. Validation error (invalid email)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Charlie", "email": "not-an-email"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        400,
        "Invalid email should return 400",
    ) {
        return;
    }

    // 8. Wrong Content-Type
    println!("\n8. Wrong Content-Type");
    let resp = client
        .post("/users")
        .header("content-type", "text/plain")
        .body(r#"{"name": "Dan", "email": "dan@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        415,
        "Wrong Content-Type should return 415",
    ) {
        return;
    }

    // 9. Delete user
    println!("\n9. Delete user");
    let resp = client.delete("/users/2").send();
    println!("   DELETE /users/2 -> {}", resp.status().as_u16());
    if !check_eq(resp.status().as_u16(), 204, "Delete user should return 204") {
        return;
    }

    // 10. Verify deletion
    println!("\n10. Verify deletion");
    let resp = client.get("/users/2").send();
    println!(
        "   GET /users/2 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Deleted user should return 404",
    ) {
        return;
    }

    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    println!("\nAll CRUD operations passed!");
}

pub fn delete<H, Fut>(self, path: impl Into<String>, handler: H) -> AppBuilder

where H: Fn(&RequestContext, &mut Request) -> Fut + Send + Sync + 'static, Fut: Future<Output = Response> + Send + 'static,

Adds a DELETE route.

Examples found in repository

examples/crud_api.rs (line 289)

fn main() {
    // Initialize the global store
    let mut guard = STORE
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner);
    *guard = Some(UserDb {
        users: HashMap::new(),
        next_id: 1,
    });

    println!("fastapi_rust CRUD API Example");
    println!("=============================\n");

    let app = App::builder()
        .post("/users", create_user)
        .get("/users", list_users)
        .get("/users/{id}", get_user)
        .put("/users/{id}", update_user)
        .delete("/users/{id}", delete_user)
        .build();

    println!("App created with {} route(s)\n", app.route_count());
    let client = TestClient::new(app);

    // 1. Create users
    println!("1. Create users");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice", "email": "alice@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Bob", "email": "bob@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    // 2. List users
    println!("\n2. List all users");
    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    // 3. Get user by ID
    println!("\n3. Get user by ID");
    let resp = client.get("/users/1").send();
    println!(
        "   GET /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Get user should return 200") {
        return;
    }

    // 4. Get nonexistent user
    println!("\n4. Get nonexistent user");
    let resp = client.get("/users/999").send();
    println!(
        "   GET /users/999 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Missing user should return 404",
    ) {
        return;
    }

    // 5. Update user
    println!("\n5. Update user");
    let resp = client
        .put("/users/1")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice Smith", "email": "alice.smith@example.com"}"#)
        .send();
    println!(
        "   PUT /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Update user should return 200") {
        return;
    }

    // 6. Validation: empty name
    println!("\n6. Validation error (empty name)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "", "email": "bad@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 400, "Empty name should return 400") {
        return;
    }

    // 7. Validation: invalid email
    println!("\n7. Validation error (invalid email)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Charlie", "email": "not-an-email"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        400,
        "Invalid email should return 400",
    ) {
        return;
    }

    // 8. Wrong Content-Type
    println!("\n8. Wrong Content-Type");
    let resp = client
        .post("/users")
        .header("content-type", "text/plain")
        .body(r#"{"name": "Dan", "email": "dan@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        415,
        "Wrong Content-Type should return 415",
    ) {
        return;
    }

    // 9. Delete user
    println!("\n9. Delete user");
    let resp = client.delete("/users/2").send();
    println!("   DELETE /users/2 -> {}", resp.status().as_u16());
    if !check_eq(resp.status().as_u16(), 204, "Delete user should return 204") {
        return;
    }

    // 10. Verify deletion
    println!("\n10. Verify deletion");
    let resp = client.get("/users/2").send();
    println!(
        "   GET /users/2 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Deleted user should return 404",
    ) {
        return;
    }

    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    println!("\nAll CRUD operations passed!");
}

pub fn patch<H, Fut>(self, path: impl Into<String>, handler: H) -> AppBuilder

where H: Fn(&RequestContext, &mut Request) -> Fut + Send + Sync + 'static, Fut: Future<Output = Response> + Send + 'static,

Adds a PATCH route.

pub fn middleware<M>(self, middleware: M) -> AppBuilder

where M: Middleware + 'static,

Adds middleware to the application.

Middleware is executed in the order it is added:

• before hooks run first-to-last
• after hooks run last-to-first

Examples found in repository

examples/getting_started.rs (line 77)

fn main() {
    println!("Getting Started Guide - Code Validation\n");

    // === Basic App Example ===
    println!("1. Basic app with two routes:");
    let app = App::builder()
        .get("/", hello)
        .get("/health", health)
        .build();

    println!("   Routes: {}", app.route_count());
    let client = TestClient::new(app);

    let response = client.get("/").send();
    println!(
        "   GET / -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(response.status().as_u16(), 200, "GET / should return 200") {
        return;
    }
    if !check_eq(response.text(), "Hello, World!", "GET / should return body") {
        return;
    }

    let response = client.get("/health").send();
    println!(
        "   GET /health -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /health should return 200",
    ) {
        return;
    }

    // === App with Middleware ===
    println!("\n2. App with middleware:");
    let app = App::builder()
        .middleware(RequestIdMiddleware::new())
        .middleware(SecurityHeaders::new())
        .get("/", hello)
        .build();

    let client = TestClient::new(app);
    let response = client.get("/").send();
    println!("   GET / -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET / with middleware should return 200",
    ) {
        return;
    }

    // === App with Configuration ===
    println!("\n3. App with configuration:");
    let config = AppConfig::new()
        .name("My API")
        .version("1.0.0")
        .debug(true)
        .max_body_size(10 * 1024 * 1024)
        .request_timeout_ms(30_000);

    let app = App::builder().config(config).get("/", hello).build();

    println!("   App name: {}", app.config().name);
    println!("   Version: {}", app.config().version);
    if !check_eq(
        app.config().name.as_str(),
        "My API",
        "Config name should match",
    ) {
        return;
    }
    if !check_eq(
        app.config().version.as_str(),
        "1.0.0",
        "Config version should match",
    ) {
        return;
    }

    // === 404 for unknown routes ===
    println!("\n4. 404 for unknown routes:");
    let app = App::builder().get("/", hello).build();

    let client = TestClient::new(app);
    let response = client.get("/nonexistent").send();
    println!("   GET /nonexistent -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        404,
        "Unknown routes should return 404",
    ) {
        return;
    }

    println!("\nAll getting started examples validated successfully!");
}

pub fn state<T>(self, state: T) -> AppBuilder

where T: Send + Sync + 'static,

Adds shared state to the application.

State can be accessed by handlers through the State<T> extractor.

pub fn exception_handler<E, H>(self, handler: H) -> AppBuilder

where E: Error + Send + Sync + 'static, H: Fn(&RequestContext, E) -> Response + Send + Sync + 'static,

Registers a custom exception handler for a specific error type.

When an error of type E occurs during request handling, the registered handler will be called to convert it into a response.

Example

#[derive(Debug)]
struct AuthError(String);

impl std::fmt::Display for AuthError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Auth error: {}", self.0)
    }
}

impl std::error::Error for AuthError {}

let app = App::builder()
    .exception_handler(|_ctx, err: AuthError| {
        Response::with_status(StatusCode::UNAUTHORIZED)
            .header("www-authenticate", b"Bearer".to_vec())
            .body_json(&json!({"error": err.0}))
    })
    .build();

pub fn exception_handlers(self, handlers: ExceptionHandlers) -> AppBuilder

Sets the exception handlers registry.

This replaces any previously registered handlers.

pub fn with_default_exception_handlers(self) -> AppBuilder

Uses default exception handlers for common error types.

This registers handlers for:

• HttpError → JSON response with status/detail
• ValidationErrors → 422 with error list

pub fn on_startup<F>(self, hook: F) -> AppBuilder

where F: FnOnce() -> Result<(), StartupHookError> + Send + 'static,

Registers a synchronous startup hook.

Startup hooks run before the server starts accepting connections, in the order they are registered (FIFO).

Example

let app = App::builder()
    .on_startup(|| {
        println!("Connecting to database...");
        Ok(())
    })
    .on_startup(|| {
        println!("Loading configuration...");
        Ok(())
    })
    .build();

pub fn on_startup_async<F, Fut>(self, hook: F) -> AppBuilder

where F: FnOnce() -> Fut + Send + 'static, Fut: Future<Output = Result<(), StartupHookError>> + Send + 'static,

Registers an async startup hook.

Async startup hooks are awaited in registration order.

Example

let app = App::builder()
    .on_startup_async(|| async {
        let pool = connect_to_database().await?;
        Ok(())
    })
    .build();

pub fn on_shutdown<F>(self, hook: F) -> AppBuilder

where F: FnOnce() + Send + 'static,

Registers a synchronous shutdown hook.

Shutdown hooks run after the server stops accepting connections and all in-flight requests complete (or are cancelled).

Shutdown hooks run in reverse registration order (LIFO), matching typical resource cleanup patterns (last acquired, first released).

Example

let app = App::builder()
    .on_shutdown(|| {
        println!("Closing database connections...");
    })
    .build();

pub fn on_shutdown_async<F, Fut>(self, hook: F) -> AppBuilder

where F: FnOnce() -> Fut + Send + 'static, Fut: Future<Output = ()> + Send + 'static,

Registers an async shutdown hook.

Async shutdown hooks are awaited in reverse registration order (LIFO).

Example

let app = App::builder()
    .on_shutdown_async(|| async {
        flush_metrics().await;
    })
    .build();

pub fn startup_hook_count(&self) -> usize

Returns the number of registered startup hooks.

pub fn shutdown_hook_count(&self) -> usize

Returns the number of registered shutdown hooks.

pub fn build(self) -> App

Builds the application.

This consumes the builder and returns the configured App.

Panics

Panics if any routes conflict (same method + structurally identical path pattern).

Examples found in repository

examples/hello_world.rs (line 82)

fn main() {
    println!("fastapi_rust Hello World Example");
    println!("================================\n");

    // Build the application
    //
    // App::builder() creates a new application builder that lets you:
    // - Add routes for different HTTP methods
    // - Configure middleware
    // - Set application state
    // - Define exception handlers
    let app = App::builder()
        // Register a GET handler for the root path "/"
        //
        // This is equivalent to:
        //   @app.get("/")
        //   def hello():
        //       return "Hello, World!"
        // in Python FastAPI
        .get("/", hello_handler)
        // Build the final immutable App
        .build();

    println!("App created with {} route(s)\n", app.route_count());

    // Create a test client to make requests to our app
    //
    // TestClient wraps any Handler (including App) and provides
    // a convenient API for making HTTP requests in tests.
    let client = TestClient::new(app);

    // Make a GET request to "/"
    println!("Making request: GET /");
    let response = client.get("/").send();

    // Check the response
    println!(
        "GET / -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    println!("Response: {}\n", response.text());

    // Verify success
    if !check_eq(response.status().as_u16(), 200, "GET / should return 200") {
        return;
    }
    if !check_eq(response.text(), "Hello, World!", "GET / should return body") {
        return;
    }

    // Try a path that doesn't exist - should get 404
    println!("Making request: GET /not-found");
    let response = client.get("/not-found").send();
    println!(
        "GET /not-found -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        404,
        "Unknown routes should return 404",
    ) {
        return;
    }

    println!("\nAll assertions passed!");
}

examples/getting_started.rs (line 42)

fn main() {
    println!("Getting Started Guide - Code Validation\n");

    // === Basic App Example ===
    println!("1. Basic app with two routes:");
    let app = App::builder()
        .get("/", hello)
        .get("/health", health)
        .build();

    println!("   Routes: {}", app.route_count());
    let client = TestClient::new(app);

    let response = client.get("/").send();
    println!(
        "   GET / -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(response.status().as_u16(), 200, "GET / should return 200") {
        return;
    }
    if !check_eq(response.text(), "Hello, World!", "GET / should return body") {
        return;
    }

    let response = client.get("/health").send();
    println!(
        "   GET /health -> {} ({})",
        response.status().as_u16(),
        response.text()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /health should return 200",
    ) {
        return;
    }

    // === App with Middleware ===
    println!("\n2. App with middleware:");
    let app = App::builder()
        .middleware(RequestIdMiddleware::new())
        .middleware(SecurityHeaders::new())
        .get("/", hello)
        .build();

    let client = TestClient::new(app);
    let response = client.get("/").send();
    println!("   GET / -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET / with middleware should return 200",
    ) {
        return;
    }

    // === App with Configuration ===
    println!("\n3. App with configuration:");
    let config = AppConfig::new()
        .name("My API")
        .version("1.0.0")
        .debug(true)
        .max_body_size(10 * 1024 * 1024)
        .request_timeout_ms(30_000);

    let app = App::builder().config(config).get("/", hello).build();

    println!("   App name: {}", app.config().name);
    println!("   Version: {}", app.config().version);
    if !check_eq(
        app.config().name.as_str(),
        "My API",
        "Config name should match",
    ) {
        return;
    }
    if !check_eq(
        app.config().version.as_str(),
        "1.0.0",
        "Config version should match",
    ) {
        return;
    }

    // === 404 for unknown routes ===
    println!("\n4. 404 for unknown routes:");
    let app = App::builder().get("/", hello).build();

    let client = TestClient::new(app);
    let response = client.get("/nonexistent").send();
    println!("   GET /nonexistent -> {}", response.status().as_u16());
    if !check_eq(
        response.status().as_u16(),
        404,
        "Unknown routes should return 404",
    ) {
        return;
    }

    println!("\nAll getting started examples validated successfully!");
}

examples/crud_api.rs (line 290)

fn main() {
    // Initialize the global store
    let mut guard = STORE
        .lock()
        .unwrap_or_else(std::sync::PoisonError::into_inner);
    *guard = Some(UserDb {
        users: HashMap::new(),
        next_id: 1,
    });

    println!("fastapi_rust CRUD API Example");
    println!("=============================\n");

    let app = App::builder()
        .post("/users", create_user)
        .get("/users", list_users)
        .get("/users/{id}", get_user)
        .put("/users/{id}", update_user)
        .delete("/users/{id}", delete_user)
        .build();

    println!("App created with {} route(s)\n", app.route_count());
    let client = TestClient::new(app);

    // 1. Create users
    println!("1. Create users");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice", "email": "alice@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Bob", "email": "bob@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 201, "Create user should return 201") {
        return;
    }

    // 2. List users
    println!("\n2. List all users");
    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    // 3. Get user by ID
    println!("\n3. Get user by ID");
    let resp = client.get("/users/1").send();
    println!(
        "   GET /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Get user should return 200") {
        return;
    }

    // 4. Get nonexistent user
    println!("\n4. Get nonexistent user");
    let resp = client.get("/users/999").send();
    println!(
        "   GET /users/999 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Missing user should return 404",
    ) {
        return;
    }

    // 5. Update user
    println!("\n5. Update user");
    let resp = client
        .put("/users/1")
        .header("content-type", "application/json")
        .body(r#"{"name": "Alice Smith", "email": "alice.smith@example.com"}"#)
        .send();
    println!(
        "   PUT /users/1 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "Update user should return 200") {
        return;
    }

    // 6. Validation: empty name
    println!("\n6. Validation error (empty name)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "", "email": "bad@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 400, "Empty name should return 400") {
        return;
    }

    // 7. Validation: invalid email
    println!("\n7. Validation error (invalid email)");
    let resp = client
        .post("/users")
        .header("content-type", "application/json")
        .body(r#"{"name": "Charlie", "email": "not-an-email"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        400,
        "Invalid email should return 400",
    ) {
        return;
    }

    // 8. Wrong Content-Type
    println!("\n8. Wrong Content-Type");
    let resp = client
        .post("/users")
        .header("content-type", "text/plain")
        .body(r#"{"name": "Dan", "email": "dan@example.com"}"#)
        .send();
    println!(
        "   POST /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        415,
        "Wrong Content-Type should return 415",
    ) {
        return;
    }

    // 9. Delete user
    println!("\n9. Delete user");
    let resp = client.delete("/users/2").send();
    println!("   DELETE /users/2 -> {}", resp.status().as_u16());
    if !check_eq(resp.status().as_u16(), 204, "Delete user should return 204") {
        return;
    }

    // 10. Verify deletion
    println!("\n10. Verify deletion");
    let resp = client.get("/users/2").send();
    println!(
        "   GET /users/2 -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(
        resp.status().as_u16(),
        404,
        "Deleted user should return 404",
    ) {
        return;
    }

    let resp = client.get("/users").send();
    println!(
        "   GET /users -> {} {}",
        resp.status().as_u16(),
        resp.text()
    );
    if !check_eq(resp.status().as_u16(), 200, "List users should return 200") {
        return;
    }

    println!("\nAll CRUD operations passed!");
}

examples/auth_example.rs (line 279)

fn main() {
    println!("fastapi_rust Authentication Example");
    println!("====================================\n");

    // Build the application with public and protected routes
    let app = App::builder()
        // Public endpoints - accessible to everyone
        .get("/public", public_handler)
        // Login endpoint - returns a token
        .post("/login", login_handler)
        // Protected endpoint - requires valid bearer token
        .get("/protected", protected_handler)
        .build();

    println!("App created with {} route(s)\n", app.route_count());

    // Create a test client
    let client = TestClient::new(app);

    // =========================================================================
    // Test 1: Public endpoint - no auth required
    // =========================================================================
    println!("1. Public endpoint - no auth required");
    let response = client.get("/public").send();
    println!(
        "   GET /public -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "GET /public should return 200",
    ) {
        return;
    }
    if !check(
        response.text().contains("public endpoint"),
        "GET /public should include the public endpoint body",
    ) {
        return;
    }

    // =========================================================================
    // Test 2: Protected endpoint - without token (should get 401)
    // =========================================================================
    println!("\n2. Protected endpoint - without token");
    let response = client.get("/protected").send();
    println!(
        "   GET /protected -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        401,
        "Protected endpoint should return 401 without token",
    ) {
        return;
    }

    // Check for WWW-Authenticate header
    let has_www_auth = response
        .headers()
        .iter()
        .any(|(name, value)| name == "www-authenticate" && value == b"Bearer");
    if !check(
        has_www_auth,
        "401 response should include WWW-Authenticate: Bearer header",
    ) {
        return;
    }

    // =========================================================================
    // Test 3: Login endpoint - get a token
    // =========================================================================
    println!("\n3. Login endpoint - get a token");
    let response = client
        .post("/login")
        .header("content-type", "application/json")
        .body(r#"{"username":"test","password":"test123"}"#)
        .send();
    println!(
        "   POST /login -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "POST /login should return 200",
    ) {
        return;
    }

    // Parse the response to get the token
    let body_text = response.text();
    let body: serde_json::Value = match serde_json::from_str(body_text) {
        Ok(body) => body,
        Err(err) => {
            eprintln!("Failed to parse login response JSON: {err}");
            return;
        }
    };
    let Some(bearer_value) = body.get("access_token").and_then(|value| value.as_str()) else {
        eprintln!("Login response missing access_token");
        return;
    };
    println!("   Bearer value: {bearer_value}");
    if !check_eq(
        bearer_value,
        DEMO_BEARER_VALUE,
        "Login should return the expected bearer value",
    ) {
        return;
    }

    // =========================================================================
    // Test 4: Protected endpoint - with valid token (should get 200)
    // =========================================================================
    println!("\n4. Protected endpoint - with valid token");
    let response = client
        .get("/protected")
        .header("authorization", format!("Bearer {DEMO_BEARER_VALUE}"))
        .send();
    println!(
        "   GET /protected (Authorization: Bearer {}) -> {} {}",
        DEMO_BEARER_VALUE,
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "Protected endpoint should return 200 with valid token",
    ) {
        return;
    }
    if !check(
        response.text().contains("protected resource"),
        "Protected endpoint should include protected resource body",
    ) {
        return;
    }

    // =========================================================================
    // Test 5: Protected endpoint - with invalid token (should get 403)
    // =========================================================================
    println!("\n5. Protected endpoint - with invalid token");
    let response = client
        .get("/protected")
        .header("authorization", "Bearer wrong_token")
        .send();
    println!(
        "   GET /protected (Authorization: Bearer wrong_token) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        403,
        "Protected endpoint should return 403 with invalid token",
    ) {
        return;
    }

    // =========================================================================
    // Test 6: Protected endpoint - with wrong auth scheme (should get 401)
    // =========================================================================
    println!("\n6. Protected endpoint - with wrong auth scheme");
    let response = client
        .get("/protected")
        .header("authorization", "Basic dXNlcjpwYXNz")
        .send();
    println!(
        "   GET /protected (Authorization: Basic ...) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        401,
        "Protected endpoint should return 401 with wrong auth scheme",
    ) {
        return;
    }

    // =========================================================================
    // Test 7: Login with wrong Content-Type (should get 415)
    // =========================================================================
    println!("\n7. Login with wrong Content-Type");
    let response = client
        .post("/login")
        .header("content-type", "text/plain")
        .body("demo=true")
        .send();
    println!(
        "   POST /login (Content-Type: text/plain) -> {} {}",
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        415,
        "Login should return 415 with wrong Content-Type",
    ) {
        return;
    }

    // =========================================================================
    // Test 8: Token case sensitivity (lowercase 'bearer')
    // =========================================================================
    println!("\n8. Token case sensitivity (lowercase 'bearer')");
    let response = client
        .get("/protected")
        .header("authorization", format!("bearer {DEMO_BEARER_VALUE}"))
        .send();
    println!(
        "   GET /protected (Authorization: bearer {}) -> {} {}",
        DEMO_BEARER_VALUE,
        response.status().as_u16(),
        response.status().canonical_reason()
    );
    if !check_eq(
        response.status().as_u16(),
        200,
        "Bearer scheme should be case-insensitive (lowercase accepted)",
    ) {
        return;
    }

    println!("\nAll authentication tests passed!");
}

Trait Implementations

impl Debug for AppBuilder

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

Formats the value using the given formatter.

impl Default for AppBuilder

fn default() -> AppBuilder

Returns the “default value” for a type.