## Usar `CORSMiddleware` { #use-corsmiddleware }

Você pode configurá-lo em sua aplicação **FastAPI** usando o `CORSMiddleware`.

* Importe `CORSMiddleware`.
* Crie uma lista de origens permitidas (como strings).
* Adicione-a como um "middleware" à sua aplicação **FastAPI**.

Você também pode especificar se o seu backend permite:

  exports okhttp3.internal.http to okhttp3.logging, okhttp3.brotli, mockwebserver3;
  exports okhttp3.internal.http2 to mockwebserver3, okhttp3.mockwebserver;
  exports okhttp3.internal.platform to okhttp3.logging, okhttp3.java.net.cookiejar, okhttp3.dnsoverhttps, mockwebserver3, okhttp3.mockwebserver, okhttp3.tls;
  exports okhttp3.internal.publicsuffix to okhttp3.dnsoverhttps;
  exports okhttp3.internal.ws to mockwebserver3, okhttp3.mockwebserver;

  requires static org.jspecify;

  exports com.google.common.collect.testing;
  exports com.google.common.collect.testing.features;
  exports com.google.common.collect.testing.google;
  exports com.google.common.collect.testing.testers;
  exports com.google.common.escape.testing;
  exports com.google.common.testing;
  exports com.google.common.util.concurrent.testing;

Asegúrate de crear un [entorno virtual](../virtual-environments.md), activarlo y luego instalarlo, por ejemplo:

```console
$ pip install httpx
```

///

Importa `TestClient`.

Crea un `TestClient` pasándole tu aplicación de **FastAPI**.

Crea funciones con un nombre que comience con `test_` (esta es la convención estándar de `pytest`).

func (e ETag) String() string {
	if e.IsMultipart() {
		return hex.EncodeToString(e[:16]) + string(e[16:])
	}
	return hex.EncodeToString(e)
}

// IsEncrypted reports whether the ETag is encrypted.
func (e ETag) IsEncrypted() bool {
	// An encrypted ETag must be at least 32 bytes long.
	// It contains the encrypted ETag value + an authentication
	// code generated by the AEAD cipher.

/// note | Détails techniques

Vous pouvez également utiliser `from starlette.middleware.cors import CORSMiddleware`.

**FastAPI** fournit plusieurs middlewares dans `fastapi.middleware` uniquement pour votre confort, en tant que développeur. Mais la plupart des middlewares disponibles proviennent directement de Starlette.

Você escreve Python padrão com tipos:

```Python
from datetime import date

from pydantic import BaseModel

# Declare uma variável como str
# e obtenha suporte do editor dentro da função
def main(user_id: str):
    return user_id


# Um modelo do Pydantic
class User(BaseModel):

from .shared import sequence_types as sequence_types
from .shared import value_is_sequence as value_is_sequence
from .v2 import ModelField as ModelField
from .v2 import PydanticSchemaGenerationError as PydanticSchemaGenerationError
from .v2 import RequiredParam as RequiredParam
from .v2 import Undefined as Undefined
from .v2 import Url as Url
from .v2 import copy_field_info as copy_field_info
from .v2 import create_body_model as create_body_model

		if i := strings.LastIndexByte(v, '/'); i >= 0 {
			v = v[i+1:]
		}
		w.Header()[xhttp.MinIOCompressed] = []string{v}
	}

	return nil
}

// needsEncoding reports whether s contains any bytes that need to be encoded.
// see mime.needsEncoding
func needsMimeEncoding(s string) bool {
	for _, b := range s {
		if (b < ' ' || b > '~') && b != '\t' {
			return true
		}
	}

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.Currency;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NavigableMap;