### CORS 预检请求 { #cors-preflight-requests }

这是些带有 `Origin` 和 `Access-Control-Request-Method` 请求头的 `OPTIONS` 请求。

在这种情况下，中间件将拦截传入的请求并进行响应，出于提供信息的目的返回一个使用了适当的 CORS headers 的 `200` 或 `400` 响应。

### 简单请求 { #simple-requests }

任何带有 `Origin` 请求头的请求。在这种情况下，中间件将像平常一样传递请求，但是在响应中包含适当的 CORS headers。

## 更多信息 { #more-info }

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing.testers;

import static com.google.common.collect.testing.features.CollectionSize.SEVERAL;
import static com.google.common.collect.testing.features.CollectionSize.ZERO;

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing.testers;

import static com.google.common.collect.testing.Helpers.copyToList;
import static com.google.common.collect.testing.Helpers.getMethod;

## Checando a documentação { #check-the-docs }

Você pode ver os headers necessários na interface gráfica da documentação em `/docs`:

<div class="screenshot">
<img src="/img/tutorial/header-param-models/image01.png">
</div>

## Proibindo Cabeçalhos adicionais { #forbid-extra-headers }

Заголовки проксі:

* [X-Forwarded-For](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-For)
* [X-Forwarded-Proto](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Proto)
* [X-Forwarded-Host](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Host)

///

También puede ayudar a evitar confusiones para nuevos desarrolladores que vean un parámetro no usado en tu código y puedan pensar que es innecesario.

///

/// info | Información

En este ejemplo usamos headers personalizados inventados `X-Key` y `X-Token`.

Pero en casos reales, al implementar seguridad, obtendrías más beneficios usando las [Utilidades de Seguridad integradas (el próximo capítulo)](../security/index.md).

///

        TensorList operations.
    *   `tf.custom_gradient` can now be applied to functions that accept nested
        structures of `tensors` as inputs (instead of just a list of tensors).
        Note that Python structures such as tuples and lists now won't be
        treated as tensors, so if you still want them to be treated that way,
        you need to wrap them with `tf.convert_to_tensor`.

                if count >= 4:
                    in_code_block4 = False
                    continue

    return headers


def remove_header_permalinks(lines: list[str]) -> list[str]:
    """
    Remove permalinks from headers in the given lines.
    """

    modified_lines: list[str] = []
    for line in lines:
        header_match = HEADER_WITH_PERMALINK_RE.match(line)

 *    * connection held ([connectionAcquired], [connectionReleased])
 *      * request ([requestFailed])
 *        * headers ([requestHeadersStart], [requestHeadersEnd])
 *        * body ([requestBodyStart], [requestBodyEnd])
 *      * response ([responseFailed])
 *        * headers ([responseHeadersStart], [responseHeadersEnd])
 *        * body ([responseBodyStart], [responseBodyEnd])
 *

  // Optional: confirm that your app made the HTTP requests you were expecting.
  val request1 = server.takeRequest()
  assertEquals("/v1/chat/messages/", request1.url.encodedPath)
  assertNotNull(request1.headers["Authorization"])

  val request2 = server.takeRequest()
  assertEquals("/v1/chat/messages/2", request2.url.encodedPath)

  val request3 = server.takeRequest()