Axum is one of the best web frameworks in the Rust community. It is a sub-project based on hyper maintained by Tokio. Axum provides web routing, declarative HTTP request parsing, HTTP response serialization, and can be combined with the middleware in the tower ecosystem.

Dependencies

spring-web = { version = "<version>" }

optional features:

http2: http2
multipart: file upload
ws: websocket
socket_io: SocketIO support
openapi: OpenAPI documentation
openapi-redoc: Redoc documentation interface
openapi-scalar: Scalar documentation interface
openapi-swagger: Swagger documentation interface

Configuration items

[web]
binding = "172.20.10.4"  # IP address of the network interface to bind, default 0.0.0.0
port = 8000              # Port number to bind, default 8080
connect_info = false     # Whether to use client connection information, default false
graceful = true          # Whether to enable graceful shutdown, default false
global_prefix = "api"    # Global prefix for all routes, default empty

# Web middleware configuration
[web.middlewares]
compression = { enable = true }                        # Enable compression middleware
catch_panic = { enable = true }                        # Capture panic generated by handler
logger = { enable = true, level = "info" }             # Enable log middleware
limit_payload = { enable = true, body_limit = "5MB" }  # Limit request body size
timeout_request = { enable = true, timeout = 60000 }   # Request timeout 60s

# Cross-domain configuration
cors = { enable = true, allow_origins = [
    "https://spring-rs.github.io",
], allow_headers = [
    "Authentication",
], allow_methods = [
    "GET",
    "POST",
], max_age = 60 }

# Static resource configuration
static = { enable = true, uri = "/static", path = "static", precompressed = true, fallback = "index.html" }

NOTE: The above middleware configuration can integrate the middleware provided in the tower ecosystem. Of course, if you are very familiar with the tower ecosystem, you can also configure it yourself by writing code without enabling these middleware. The following are relevant document links:

tower

tower-http

API interface

App implements the WebConfigurator feature, which can be used to specify routing configuration:

use spring::App;
use spring_web::{get, get_api};
use spring_web::{WebPlugin, WebConfigurator, Router, axum::response::IntoResponse, handler::TypeRouter};
use spring_sqlx::SqlxPlugin;

#[tokio::main]
async fn main() {
    App::new()
      .add_plugin(SqlxPlugin)
      .add_plugin(WebPlugin)
      .add_router(router())
      .run()
      .await
}

fn router() -> Router {
    Router::new().typed_route(hello_word)
}

#[get("/")]
async fn hello_word() -> impl IntoResponse {
   "hello word"
}

/// # The API summary title must use the head-1 in Markdown format.
/// description
/// description support multi line
/// The get_api macro automatically collects the request parameters and response schema.
/// @tag api_tag
#[get_api("/api")]
async fn hello_api() -> String {
   "hello api".to_string()
}

You can also use the auto_config macro to implement automatic configuration. This process macro will automatically register the routes marked by the Procedural Macro into the app:

+#[auto_config(WebConfigurator)]
 #[tokio::main]
 async fn main() {
    App::new()
    .add_plugin(SqlxPlugin)
    .add_plugin(WebPlugin)
-   .add_router(router())
    .run()
    .await
}

-fn router() -> Router {
-    Router::new().typed_route(hello_word)
-}

Attribute macro

In the example above, get is an attribute macro. spring-web provides procedural macros for eight standard HTTP methods: get, post, patch, put, delete, head, trace, and options. It also provides eight macros for generating OpenAPI documentation, such as get_api and post_api.

You can also use the route or api_route macros to bind multiple methods simultaneously:

use spring_web::route;
use spring_web::axum::response::IntoResponse;

#[route("/test", method = "GET", method = "HEAD")]
async fn example() -> impl IntoResponse {
    "hello world"
}

In addition, spring also supports binding multiple routes to a handler, which requires the routes attribute macro:

use spring_web::{routes, get, delete};
use spring_web::axum::response::IntoResponse;

#[routes]
#[get("/test")]
#[get("/test2")]
#[delete("/test")]
async fn example() -> impl IntoResponse {
    "hello world"
}

Extract the Component registered by the plugin

In the above example, the SqlxPlugin plugin automatically registers a Sqlx connection pool component for us. We can use Component to extract this connection pool from State. Component is an axum extractor.

use anyhow::Context;
use spring_web::get;
use spring_web::{axum::response::IntoResponse, extractor::Component, error::Result};
use spring_sqlx::{ConnectPool, sqlx::{self, Row}};

#[get("/version")]
async fn mysql_version(Component(pool): Component<ConnectPool>) -> Result<String> {
    let version = sqlx::query("select version() as version")
        .fetch_one(&pool)
        .await
        .context("sqlx query failed")?
        .get("version");
    Ok(version)
}

Axum also provides other extractors, which are reexported under spring_web::extractor.

Read configuration

You can use Config to extract the configuration in the toml file.

use spring_web::get;
use spring_web::{extractor::Config, axum::response::IntoResponse};
use spring::config::Configurable;
use serde::Deserialize;

#[derive(Debug, Configurable, Deserialize)]
#[config_prefix = "custom"]
struct CustomConfig {
    a: u32,
    b: bool,
}

#[get("/config")]
async fn use_toml_config(Config(conf): Config<CustomConfig>) -> impl IntoResponse {
    format!("a={}, b={}", conf.a, conf.b)
}

Add the corresponding configuration to your configuration file:

[custom]
a = 1
b = true

Complete code reference web-example

Use Extractor in Middleware

You can also use Extractor in middleware, but please note that you need to follow the rules of axum.

use spring_web::{middlewares, axum::middleware};

/// you can apply this middleware to your routes using the `middlewares` macro:
#[middlewares(
    middleware::from_fn(problem_middleware),
)]
mod routes {
    use spring_web::{axum::{response::Response, middleware::Next, response::IntoResponse}, extractor::{Request, Component}};
    use spring_sqlx::ConnectPool;
    use spring_web::{middlewares, get, axum::middleware};
    use std::time::Duration;

    async fn problem_middleware(Component(db): Component<ConnectPool>, request: Request, next: Next) -> Response {
        // do something
        let response = next.run(request).await;

        response
    }

    #[get("/")]
    async fn hello_world() -> impl IntoResponse {
        "hello world"
    }

}

This middleware will:

Intercept all responses from routes in the module

Complete code reference web-middleware-example

spring-web is a thin wrapper around axum, adding some macros to simplify development. The examples of axum can be run in spring-web.

SocketIO support

You can enable the socket_io feature of spring-web to use a integration with socketioxide.

SocketIO is a implementation of WebSocket with more definitions.

Named events (like chat message, user joined, etc.) instead of just plain messages
Automatic reconnection if the connection is lost
Heartbeat mechanism to detect dead connections
Rooms / Namespaces to group clients
Fallbacks to other transports if WebSocket isn't available

You can refer to the socketio-example for a example of using SocketIO in spring-web.

We can share components registered by plugins in SocketIO handlers, just like in normal HTTP handlers, for example, using the Sqlx connection pool component registered by the SqlxPlugin plugin.

OpenAPI support

You can enable the openapi feature of spring-web to use OpenAPI documentation generation. You can refer to the openapi-example for more information.

Besides you need to enable one of the documentation interface features: openapi-redoc, openapi-scalar or openapi-swagger to generate the corresponding documentation interface.

/// Always return error  
/// 
/// This endpoint is annotated with status_codes for Errors::B and Errors::C
/// @tag error
/// @status_codes Errors::B, Errors::C, Errors::SqlxError, Errors::TeaPod
#[get_api("/error")]
async fn error() -> Result<Json<String>, Errors> {
    Err(Errors::B)
}

To generate OpenAPI documentation, you can use the get_api, post_api, etc. macros to define your API endpoints. These macros will automatically collect request parameters and response schemas to generate OpenAPI documentation.

The comments above the API function are used to provide additional information for the OpenAPI documentation, such as tags and status codes.

The status_codes annotation specifies the possible error types that the API may return. This information will be included in the OpenAPI documentation, allowing users to understand the potential error responses when calling this API.

In case of want to define custom error types, you must implement the HttpStatusCode trait for your error type, which is used to map the error to an HTTP status code in the OpenAPI documentation.

We can use the derive macro ProblemDetails to automatically implement both the HttpStatusCode and ToProblemDetails traits for our custom error type.

In this case we are implementing thiserror::Error for better error handling, but it's not mandatory.

use spring_web::ProblemDetails;
use spring_web::axum::http::StatusCode;

#[derive(thiserror::Error, Debug, ProblemDetails)]
pub enum CustomErrors {
    #[status_code(400)]
    #[error("A basic error occurred")]
    ABasicError,

    #[status_code(500)]
    #[error(transparent)]
    SqlxError(#[from] spring_sqlx::sqlx::Error),

    #[status_code(418)]
    #[error("TeaPod error occurred: {0:?}")]
    TeaPod(CustomErrorSchema),
}

#[derive(Debug, JsonSchema)]
pub struct CustomErrorSchema {
    pub code: u16,
    pub message: String,
}

Simplified Error Handling with Automatic Problem Details

The ProblemDetails derive macro automatically generates both HttpStatusCode and ToProblemDetails implementations, eliminating the need for manual mapping:

use spring_web::ProblemDetails;

// Only need ProblemDetails derive - HttpStatusCode and ToProblemDetails are generated automatically!
#[derive(thiserror::Error, Debug, ProblemDetails)]
pub enum ApiErrors {
    // Basic usage - uses about:blank as problem type
    #[status_code(400)]
    #[error("Validation failed")]
    ValidationError,

    // Custom problem type with full URI
    #[status_code(401)]
    #[problem_type("https://api.myapp.com/problems/authentication-required")]
    #[error("Authentication required")]
    AuthenticationError,

    // Custom problem type with all fields
    #[status_code(404)]
    #[problem_type("https://api.myapp.com/problems/resource-not-found")]
    #[title("Resource Not Found")]
    #[detail("The requested resource could not be found")]
    #[error("Resource not found")]
    NotFoundError,
}

impl IntoResponse for ApiErrors {
    fn into_response(self) -> Response {
        // Both HttpStatusCode and ToProblemDetails are automatically implemented!
        self.to_problem_details().into_response()
    }
}

The macro automatically maps common HTTP status codes to appropriate Problem Details:

400 → ProblemDetails::validation_error() (uses about:blank)
401 → ProblemDetails::authentication_error() (uses about:blank)
403 → ProblemDetails::authorization_error() (uses about:blank)
404 → ProblemDetails::not_found() (uses about:blank)
500 → ProblemDetails::internal_server_error() (uses about:blank)
503 → ProblemDetails::service_unavailable() (uses about:blank)
Other codes → Uses about:blank as problem type

Advanced Problem Details with Custom Attributes

The ProblemDetails derive macro supports additional attributes for fine-grained control over the generated Problem Details:

use spring_web::ProblemDetails;

#[derive(thiserror::Error, Debug, ProblemDetails)]
pub enum ApiError {
    // Basic usage - auto-generated fields
    #[status_code(400)]
    #[error("Validation failed")]
    BasicValidation,

    // Custom problem type and title
    #[status_code(400)]
    #[problem_type("https://api.myapp.com/problems/field-validation")]
    #[title("Field Validation Error")]
    #[error("Field validation failed")]
    FieldValidation,

    // Full customization
    #[status_code(403)]
    #[problem_type("https://api.myapp.com/problems/insufficient-permissions")]
    #[title("Insufficient Permissions")]
    #[detail("You need admin privileges to perform this action")]
    #[instance("/admin/users")]
    #[error("Access denied")]
    InsufficientPermissions,
}

Supported Attributes

#[status_code(code)] - Required: HTTP status code
#[problem_type("uri")] - Optional: Custom problem type URI
#[title("title")] - Optional: Custom problem title
#[detail("detail")] - Optional: Custom problem detail message
#[instance("uri")] - Optional: Problem instance URI

Title Compatibility

The title field can be automatically derived from the #[error("...")] attribute if no explicit #[title("...")] is provided. This provides compatibility with thiserror::Error and reduces duplication:

#[derive(thiserror::Error, Debug, ProblemDetails)]
pub enum ApiError {
    // Title explicitly set
    #[status_code(400)]
    #[title("Custom Validation Error")]
    #[error("Validation failed")]
    ExplicitTitle,
    
    // Title derived from error attribute
    #[status_code(422)]
    #[detail("Request data is invalid")]
    #[error("Validation Failed")]  // This becomes the title
    ImplicitTitle,
}

Generated Response Examples

BasicValidation (auto-generated):

{
  "type": "about:blank/basic-validation",
  "title": "Basic Validation Error",
  "status": 400,
  "detail": "BasicValidation occurred"
}

InsufficientPermissions (fully customized):

{
  "type": "https://api.myapp.com/problems/insufficient-permissions",
  "title": "Insufficient Permissions",
  "status": 403,
  "detail": "You need admin privileges to perform this action",
  "instance": "/admin/users"
}

#[tokio::main]
async fn main() {
    App::new()
        .add_plugin(WebPlugin)
        .run()
        .await;
}

Then implement error handling:

use spring_web::ProblemDetails;

#[derive(thiserror::Error, Debug, ProblemDetails)]
pub enum CustomErrors {
    // Basic usage - uses about:blank as problem type
    #[status_code(400)]
    #[error("A basic error occurred")]
    ABasicError,

    // Custom problem type
    #[status_code(500)]
    #[problem_type("https://api.myapp.com/problems/database-error")]
    #[error(transparent)]
    SqlxError(#[from] spring_sqlx::sqlx::Error),

    #[status_code(418)]
    #[error("TeaPod error occurred: {0:?}")]
    TeaPod(CustomErrorSchema),
}

// Implement Problem Details conversion
impl ToProblemDetails for CustomErrors {
    fn to_problem_details(&self) -> ProblemDetails {
        match self {
            CustomErrors::ABasicError => {
                ProblemDetails::validation_error("A basic validation error occurred")
            }
            CustomErrors::SqlxError(err) => {
                ProblemDetails::custom_problem(
                    "database-error",
                    "Database Error", 
                    500,
                ).with_detail(format!("Database operation failed: {}", err))
            }
            CustomErrors::TeaPod(schema) => {
                ProblemDetails::custom_problem(
                    "teapot-error",
                    "I'm a teapot",
                    418,
                ).with_detail(format!("TeaPod error: {}", schema.message))
            }
        }
    }
}

impl IntoResponse for CustomErrors {
    fn into_response(self) -> Response {
        self.to_problem_details().into_response()
    }
}

The Problem Details response will be formatted as:

{
  "type": "https://api.myapp.com/problems/validation-error",
  "title": "Validation Error",
  "status": 400,
  "detail": "A basic validation error occurred"
}

Automatic Instance URI Capture

Problem Details automatically captures the current request URI and includes it in the instance field. This feature is enabled by default and requires no additional configuration:

// No middleware configuration needed - it's automatic!

#[get_api("/users/{id}")]
async fn get_user(Path(id): Path<u32>) -> Result<Json<User>, ApiError> {
    if id == 999 {
        // The instance field will automatically be set to "/users/999"
        return Err(ApiError::NotFound);
    }
    
    Ok(Json(User { id, name: "User".to_string() }))
}

This will automatically generate responses with the request URI:

{
  "type": "about:blank",
  "title": "Resource Not Found",
  "status": 404,
  "detail": "The requested resource was not found",
  "instance": "/users/999"
}

spring-web 0.4.16