Middleware

Middleware is a function which is called before the route handler. Middleware functions have access to the request and response objects, and the next() middleware function in the application’s request-response cycle.

NestForge middleware are, by default, equivalent to Axum/Tower middleware. They are the perfect place to handle low-level HTTP concerns.

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Creating Middleware

The easiest way to create a middleware is using the nestforge::middleware! macro.

use nestforge::middleware;

middleware!(LoggerMiddleware, |req, next| {
    println!("Incoming Request: {} {}", req.method(), req.uri().path());

    // Call the next middleware/handler in the chain
    let res = (next)(req).await;

    println!("Outgoing Response: {}", res.status());
    res
});

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Applying Middleware

In NestForge, you configure middleware within the NestForgeFactory during application bootstrap. You can apply middleware globally or to specific routes.

Global Middleware

To apply a middleware to every single route in your application:

src/main.rs

NestForgeFactory::<AppModule>::create()?
    .use_middleware::<LoggerMiddleware>()
    .listen(3000)
    .await?;

Targeted Middleware

You can use the .configure_middleware() builder to apply middleware selectively.

NestForgeFactory::<AppModule>::create()?
    .configure_middleware(|consumer| {
        // Apply to all routes
        consumer.apply::<LoggerMiddleware>().for_all_routes();

        // Apply only to /users prefixed routes
        consumer.apply::<AuthMiddleware>().for_routes(["/users"]);

        // Apply to /admin but exclude the health check
        consumer.apply::<AuditMiddleware>()
            .exclude(["/admin/health"])
            .for_routes(["/admin"]);

        consumer
    })
    .listen(3000)
    .await?;

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When to use Middleware?

Middleware is best suited for cross-cutting HTTP concerns that don’t require knowledge of the specific route handler being executed.

• Request Logging: Logging details about every hit.
• CORS Configuration: Handling Cross-Origin Resource Sharing.
• Header Manipulation: Adding or removing standard HTTP headers.
• Compression: Gzip/Brotli encoding of responses.
• Request ID Tracking: Generating and attaching unique IDs to every request.

Caution

If your logic depends on Authorization or Roles, you should almost always use a Guard instead. Guards are executed after middleware and have better access to the application context.

Dependency Injection in Middleware

NestForge middleware can also benefit from dependency injection. Since they are registered via the factory, they can resolve providers registered in your modules.

pub struct AuthMiddleware {
    config: Inject<ConfigService>,
}

middleware!(AuthMiddleware, |req, next| {
   // Access self.config here
   (next)(req).await
});