var canUseHeaderValue = true
  var headerValue: String? = null

  loop@ for (i in 0 until headers.size) {
    val name = headers.name(i)
    val value = headers.value(i)

    when {
      name.equals("Cache-Control", ignoreCase = true) -> {
        if (headerValue != null) {
          // Multiple cache-control headers means we can't use the raw value.
          canUseHeaderValue = false
        } else {

		}
	}
}

// Tests validate metadata extraction from http headers.
func TestExtractMetadataHeaders(t *testing.T) {
	testCases := []struct {
		header     http.Header
		metadata   map[string]string
		shouldFail bool
	}{
		// Validate if there a known 'content-type'.
		{
			header: http.Header{
				"Content-Type": []string{"image/png"},
			},
			metadata: map[string]string{

      Request.Builder()
        .url(server.url("/"))
        .header("Connection", "close")
        .build()
    val requestB = Request(server.url("/"))
    assertConnectionNotReused(requestA, requestB)
  }

  @Test
  fun connectionsAreNotReusedWithResponseConnectionClose() {
    server.enqueue(
      MockResponse(
        headers = headersOf("Connection", "close"),
        body = "a",
      ),
    )

def test_get_invalid_one_header_items(client: TestClient):
    response = client.get("/items/", headers={"X-Token": "invalid"})
    assert response.status_code == 400, response.text
    assert response.json() == {"detail": "X-Token header invalid"}


@needs_py39
def test_get_invalid_one_users(client: TestClient):
    response = client.get("/users/", headers={"X-Token": "invalid"})
    assert response.status_code == 400, response.text

* 创建一个允许的源列表（由字符串组成）。
* 将其作为「中间件」添加到你的 **FastAPI** 应用中。

你也可以指定后端是否允许：

* 凭证（授权 headers，Cookies 等）。
* 特定的 HTTP 方法（`POST`，`PUT`）或者使用通配符 `"*"` 允许所有方法。
* 特定的 HTTP headers 或者使用通配符 `"*"` 允许所有 headers。

```Python hl_lines="2  6-11  13-19"
{!../../docs_src/cors/tutorial001.py!}
```

默认情况下，这个 `CORSMiddleware` 实现所使用的默认参数较为保守，所以你需要显式地启用特定的源、方法或者 headers，以便浏览器能够在跨域上下文中使用它们。

支持以下参数：

	public final fun addUnsafeNonAscii (Ljava/lang/String;Ljava/lang/String;)Lokhttp3/Headers$Builder;
	public final fun build ()Lokhttp3/Headers;
	public final fun get (Ljava/lang/String;)Ljava/lang/String;
	public final fun removeAll (Ljava/lang/String;)Lokhttp3/Headers$Builder;
	public final fun set (Ljava/lang/String;Ljava/lang/String;)Lokhttp3/Headers$Builder;

async def get_current_user(token: str = Depends(oauth2_scheme)):
    credentials_exception = HTTPException(
        status_code=status.HTTP_401_UNAUTHORIZED,
        detail="Could not validate credentials",
        headers={"WWW-Authenticate": "Bearer"},
    )
    try:
        payload = jwt.decode(token, SECRET_KEY, algorithms=[ALGORITHM])
        username: str = payload.get("sub")
        if username is None:

    }

    val recorded = server.takeRequest()
    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")
    assertThat(recorded.headers["Accept-Encoding"]).isEqualTo("gzip, x-gzip, deflate")
    assertThat(recorded.headers["Connection"]).isEqualTo("keep-alive")
    assertThat(recorded.headers["User-Agent"]!!).startsWith("Apache-HttpClient/")
  }

                    if (properties != null && properties.length > 0) {
                        headers = new HashMap<>();
                        for (PlexusConfiguration property : properties) {
                            headers.put(
                                    property.getChild("name").getValue(),
                                    property.getChild("value").getValue());

type Identity struct {
	Type        string `json:"type"`
	PrincipalID string `json:"principalId"`
	AccessKeyID string `json:"accessKeyId"`
}

// UserRequest user request headers
type UserRequest struct {
	URL     string      `json:"url"`
	Headers http.Header `json:"headers"`
}

// GetObjectContext provides the necessary details to perform
// download of the object, and return back the processed response
// to the server.