# CORS (Cross-Origin Resource Sharing) { #cors-cross-origin-resource-sharing }

<a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS" class="external-link" target="_blank">CORS o "Cross-Origin Resource Sharing"</a> se refiere a situaciones en las que un frontend que se ejecuta en un navegador tiene código JavaScript que se comunica con un backend, y el backend está en un "origen" diferente al frontend.

## Origen { #origin }

This way, you can get the best of both worlds: type annotations with **tooling support** and **data filtering**.

## See it in the docs { #see-it-in-the-docs }

When you see the automatic docs, you can check that the input model and output model will both have their own JSON Schema:

<img src="/img/tutorial/response-model/image01.png">

## Snapshots and Documentation

Snapshots of Guava built from the `master` branch are available through Maven
using version `999.0.0-HEAD-jre-SNAPSHOT`, or `999.0.0-HEAD-android-SNAPSHOT`
for the Android flavor.

[Snapshot API Javadoc][guava-snapshot-api-docs] as well as

  - [beta] StatefulSets allow workloads that require persistent identity or per-instance storage to be created and managed on Kubernetes. ([docs](http://kubernetes.io/docs/concepts/abstractions/controllers/statefulsets/)) ([kubernetes/features#137](https...

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

You can read more about this in the [Advanced User Guide](../advanced/index.md){.internal-link target=_blank}.

## Details { #details }

@SdkSuppress(minSdkVersion = 34)
class AndroidHttpEngineTest {
  val context = InstrumentationRegistry.getInstrumentation().context

  val cacheDir =
    context.cacheDir.resolve("httpEngine").also {
      it.mkdirs()
    }
  val engine =
    HttpEngine
      .Builder(context)
      .setEnableBrotli(true)
      .setStoragePath(cacheDir.path)
      .setEnableHttpCache(HttpEngine.Builder.HTTP_CACHE_DISK, 10_000_000)

  - [alpha] Access Review APIs expose authorization engine to external inquiries for delegation, inspection, and debugging ([docs](http://kubernetes.io/docs/admin/authorization/)) ([kubernetes/features#37](https://github.com/kubernetes/enhancements/issues/37))...

Но FastAPI также поддерживает использование <a href="https://docs.python.org/3/library/dataclasses.html" class="external-link" target="_blank">`dataclasses`</a> тем же способом:

{* ../../docs_src/dataclasses_/tutorial001_py310.py hl[1,6:11,18:19] *}

{* ../../docs_src/middleware/tutorial001_py39.py hl[8:9,11,14] *}

/// tip | Примечание

Имейте в виду, что можно добавлять свои собственные заголовки <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">при помощи префикса 'X-'</a>.

//// tab | Pydantic v2

У версії Pydantic 2 використовується атрибут `model_config`, який приймає `dict`, як описано в <a href="https://docs.pydantic.dev/latest/api/config/" class="external-link" target="_blank">документації Pydantic: Конфігурація</a>.