# Middleware

## Overview

Middleware is useful for adding other libs for additional features. Local middleware will be replaced with **AOP** soon.

{% hint style="danger" %}
**Note, current middleware API is experimental. There can be breaking changes in next release.**
{% endhint %}

For now, middleware is pretty trivial. You can use **@Middleware** decorator and define it on route or on whole controller.

Simple example: 

```typescript
import { Controller, IController, Get, Middleware, IRouterContext } from "odi";

const logUrl= (context: IRouterContext, next: () => Promise<any>) => {
    console.log(context.request.url);
    next();
}

@Controller()
export class SampleController extends IController {
      
    @Middleware(logUrl)
    @Get index() {
        return `Hello, world from index !`;
    }

    @Get about() {
        return `Hello, world from about !`;
    }
}
```

## Decorators

There are only 1 decorator for middleware purposes.&#x20;

* `@Middleware(...functions: MiddlewareFunction[]` - set middleware for only one path, or set middleware for whole controller. Accepts unlimited number of middleware functions.&#x20;

Don't forget about function context. You should set it manually or use lambda functions instead.

## Purposes

Unfortunately, due to middleware structure, dependency injection cannot be applied for middleware functions. It should be used only for request data preprocessing, parsing and etc.&#x20;

{% hint style="success" %}
Check out future releases for **AOP**

AOP will solve most middleware cases
{% endhint %}