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 {

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 void setHeaders(final Map<String, List<String>> headers) {
        if (headers != null) {
            final Map<String, List<String>> map = new HashMap<>();
            headers.entrySet().stream().filter(e -> e.getKey() != null)
                    .forEach(e -> map.put(e.getKey().toLowerCase(Locale.ROOT), e.getValue()));
            this.headers = map;
        }
    }

	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;

    }

    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/")
  }

def test_gzip_request(compress):
    n = 1000
    headers = {}
    body = [1] * n
    data = json.dumps(body).encode()
    if compress:
        data = gzip.compress(data)
        headers["Content-Encoding"] = "gzip"
    headers["Content-Type"] = "application/json"
    response = client.post("/sum", content=data, headers=headers)
    assert response.json() == {"sum": n}


def test_request_class():

		if crypto.SSECopy.IsRequested(r.Header) {
			writeErrorResponse(ctx, w, toAPIError(ctx, errInvalidEncryptionParameters), r.URL)
			return
		}

		if crypto.SSEC.IsRequested(r.Header) && crypto.S3.IsRequested(r.Header) {
			writeErrorResponse(ctx, w, toAPIError(ctx, crypto.ErrIncompatibleEncryptionMethod), r.URL)
			return
		}

		if crypto.SSEC.IsRequested(r.Header) && crypto.S3KMS.IsRequested(r.Header) {

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.

        method = self.METHOD

        def fetch_credentials():
            # HTTP headers are case insensitive filter out
            # all duplicate headers and pick one.
            headers = {}
            headers['content-type'] = 'application/x-www-form-urlencoded'
            headers['authorization'] = urllib3.make_headers(
                basic_auth='%s:%s' % (self.cid, self.csec))['authorization']