# Internal Message Handler

The Internal Handler connecting any service available in Depedency Container to an input channel so that it may play the role of a [Endpoint](https://docs.ecotone.tech/messaging/messaging-concepts/message-endpoint). If the service produces output, it may also be connected to an output channel.

### How to register

```php
class Shop
{
    #[InternalHandler("buyProduct")] 
    public function buyProduct(int $productId) : void
    {
        echo "Product with id {$productId} was bought";
    }
}
```

### Possible options

* `endpointId` - Endpoint identifier
* `inputChannnelName` - Required option, defines to which channel endpoint should be connected
* `outputChannelName` - Channel where result of method invocation will be
* `requiredInterceptorNames` - List of [interceptor](https://docs.ecotone.tech/modelling/extending-messaging-middlewares/interceptors) names, which should intercept the endpoint