# `Request` class

You can declare a parameter in a *path operation function* or dependency to be of type `Request` and then you can access the raw request object directly, without any validation, etc.

Read more about it in the [FastAPI docs about using Request directly](https://fastapi.tiangolo.com/advanced/using-request-directly/)

You can import it directly from `fastapi`:

```python
from fastapi import Request
```

/// tip

## Parameterized dependencies { #parameterized-dependencies }

All the dependencies we have seen are a fixed function or class.

But there could be cases where you want to be able to set parameters on the dependency, without having to declare many different functions or classes.

Let's imagine that we want to have a dependency that checks if the query parameter `q` contains some fixed content.

But we want to be able to parameterize that fixed content.

  @J2ktIncompatible // Incompatible return type change. Use inherited implementation
  public Object[] toArray() {
    /*
     * If we could, we'd declare the no-arg `Collection.toArray()` to return "Object[] but elements
     * have the same nullness as E." Since we can't, we declare it to return nullable elements, and
     * we can override it in our non-null-guaranteeing subtypes to present a better signature to
     * their users.
     *

  public void testNulls() {
    try {
      Class.forName("java.lang.reflect.AnnotatedType");
    } catch (ClassNotFoundException runningInAndroidVm) {
      /*
       * Parameter declares a method that returns AnnotatedType, which isn't available on Android.
       * This would cause NullPointerTester, which calls Class.getDeclaredMethods, to throw
       * NoClassDefFoundError.
       */
      return;
    }

  public void testNulls() {
    try {
      Class.forName("java.lang.reflect.AnnotatedType");
    } catch (ClassNotFoundException runningInAndroidVm) {
      /*
       * Parameter declares a method that returns AnnotatedType, which isn't available on Android.
       * This would cause NullPointerTester, which calls Class.getDeclaredMethods, to throw
       * NoClassDefFoundError.
       */
      return;
    }

{* ../../docs_src/server_sent_events/tutorial001_py310.py ln[1:25] hl[4,22] *}

Chaque élément produit avec `yield` est encodé en JSON et envoyé dans le champ `data:` d’un événement SSE.

Si vous déclarez le type de retour comme `AsyncIterable[Item]`, FastAPI l’utilisera pour **valider**, **documenter** et **sérialiser** les données avec Pydantic.

{* ../../docs_src/server_sent_events/tutorial001_py310.py ln[1:25] hl[10:12,23] *}

# Headers de Response { #response-headers }

## Usa un parámetro `Response` { #use-a-response-parameter }

Puedes declarar un parámetro de tipo `Response` en tu *path operation function* (como puedes hacer para cookies).

Y luego puedes establecer headers en ese objeto de response *temporal*.

{* ../../docs_src/response_headers/tutorial002_py310.py hl[1, 7:8] *}

#dependencies-for-groups-of-path-operations }

Later, when reading about how to structure bigger applications ([Bigger Applications - Multiple Files](../../tutorial/bigger-applications.md)), possibly with multiple files, you will learn how to declare a single `dependencies` parameter for a group of *path operations*....

/**
 * Runtime exception wrapper for ServletException.
 *
 * This exception is used to wrap checked ServletExceptions and convert them
 * into unchecked RuntimeExceptions, allowing them to be thrown from methods
 * that don't declare ServletException in their throws clause.
 */
public class ServletRuntimeException extends RuntimeException {

    /** Serial version UID for serialization compatibility. */
    private static final long serialVersionUID = 1L;

```

::: fastapi.Depends

## `Security()`

For many scenarios, you can handle security (authorization, authentication, etc.) with dependencies, using `Depends()`.

But when you want to also declare OAuth2 scopes, you can use `Security()` instead of `Depends()`.

You can import `Security()` directly from `fastapi`:

```python
from fastapi import Security
```