if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

      System.out.println("Server: " + response.header("Server"));
      System.out.println("Date: " + response.header("Date"));
      System.out.println("Vary: " + response.headers("Vary"));
    }
  }

  public static void main(String... args) throws Exception {
    new AccessHeaders().run();
  }

describing the request at a high-level: _“fetch me this URL with these headers.”_ For correctness and efficiency, OkHttp rewrites your request before transmitting it.

OkHttp may add headers that are absent from the original request, including `Content-Length`, `Transfer-Encoding`, `User-Agent`, `Host`, `Connection`, and `Content-Type`. It will add an `Accept-Encoding` header for transparent response compression unless the header is already present. If you’ve got cookies, OkHttp will add a `Cookie`...

{* ../../docs_src/advanced_middleware/tutorial001_py39.py hl[2,6] *}

## `TrustedHostMiddleware` { #trustedhostmiddleware }

Enforces that all incoming requests have a correctly set `Host` header, in order to guard against HTTP Host Header attacks.

{* ../../docs_src/advanced_middleware/tutorial002_py39.py hl[2,6:8] *}

The following arguments are supported:

		listObjectsV2Info ListObjectsV2Info
		err               error
	)

	if r.Header.Get(xMinIOExtract) == "true" && strings.Contains(prefix, archivePattern) {
		// Initiate a list objects operation inside a zip file based in the input params
		listObjectsV2Info, err = listObjectsV2InArchive(ctx, objectAPI, bucket, prefix, token, delimiter, maxKeys, startAfter, r.Header)
	} else {
		// Initiate a list objects operation based on the input params.

Estos son cualquier request `OPTIONS` con headers `Origin` y `Access-Control-Request-Method`.

En este caso, el middleware interceptará el request entrante y responderá con los headers CORS adecuados, y un response `200` o `400` con fines informativos.

### Requests simples { #simple-requests }

	req, _ := http.NewRequest(http.MethodOptions, s.endPoint, nil)
	req.Header.Set("Origin", "http://foobar.com")
	res, err := s.client.Do(req)
	if err != nil {
		c.Fatal(err)
	}

	for k := range expectedMap {
		if v, ok := res.Header[k]; !ok {
			c.Errorf("Expected key %s missing from %v", k, res.Header)
		} else {
			expectedSet := set.CreateStringSet(expectedMap[k]...)

* `content` - A `str` or `bytes`.
* `status_code` - An `int` HTTP status code.
* `headers` - A `dict` of strings.
* `media_type` - A `str` giving the media type. E.g. `"text/html"`.

FastAPI (actually Starlette) will automatically include a Content-Length header. It will also include a Content-Type header, based on the `media_type` and appending a charset for text types.

## Einen `Response`-Parameter verwenden { #use-a-response-parameter }

Sie können einen Parameter vom Typ `Response` in Ihrer *Pfadoperation-Funktion* deklarieren (wie Sie es auch für Cookies und Header tun können).

Anschließend können Sie den `status_code` in diesem *vorübergehenden* <abbr title="Response – Antwort: Daten, die der Server zum anfragenden Client zurücksendet">Response</abbr>-Objekt festlegen.

	c, err := GetContentChecksum(r.Header)
	if err != nil || c == nil {
		return
	}
	t, s := c.Type, c.Encoded
	if !c.Type.IsSet() {
		return
	}
	if c.Type.Is(ChecksumTrailing) {
		val := r.Trailer.Get(t.Key())
		if val != "" {
			w.Header().Set(t.Key(), val)
		}
		return
	}
	w.Header().Set(t.Key(), s)
}

    assertThat(request.header("Referer")).isEqualTo("foo")
    assertThat(request.body).isNull()
  }

  @Test
  fun userAgent() {
    val request = fromArgs("-A", "foo", "http://example.com").createRequest()
    assertThat(request.method).isEqualTo("GET")
    assertThat(request.url.toString()).isEqualTo("http://example.com/")
    assertThat(request.header("User-Agent")).isEqualTo("foo")