# `Response` class

You can declare a parameter in a *path operation function* or dependency to be of type `Response` and then you can set data for the response like headers or cookies.

You can also use it directly to create an instance of it and return it from your *path operations*.

You can import it directly from `fastapi`:

```python
from fastapi import Response
```

你也可以在直接返回`Response`时添加头部。

按照[直接返回响应](response-directly.md){.internal-link target=_blank}中所述创建响应，并将头部作为附加参数传递：
```Python hl_lines="10-12"
{!../../../docs_src/response_headers/tutorial001.py!}
```


!!! note "技术细节"
    你也可以使用`from starlette.responses import Response`或`from starlette.responses import JSONResponse`。

    **FastAPI**提供了与`fastapi.responses`相同的`starlette.responses`，只是为了方便开发者。但是，大多数可用的响应都直接来自Starlette。

Cela peut être utile, par exemple, pour retourner des en-têtes personnalisés ou des cookies.

## Renvoyer une `Response`

En fait, vous pouvez retourner n'importe quelle `Response` ou n'importe quelle sous-classe de celle-ci.

!!! note "Remarque"
    `JSONResponse` est elle-même une sous-classe de `Response`.

Et quand vous retournez une `Response`, **FastAPI** la transmet directement.

    Of course, the actual `Content-Type` header, status code, etc, will come from the `Response` object you returned.

### Document in OpenAPI and override `Response`

If you want to override the response from inside of the function but at the same time document the "media type" in OpenAPI, you can use the `response_class` parameter AND return a `Response` object.

### `response_model` Priority

If you declare both a return type and a `response_model`, the `response_model` will take priority and be used by FastAPI.

	w.WriteHeader(statusCode)
	if response != nil {
		w.Write(response)
	}
}

// mimeType represents various MIME type used API responses.
type mimeType string

const (
	// Means no response type.
	mimeNone mimeType = ""
	// Means response type is JSON.
	mimeJSON mimeType = "application/json"
	// Means response type is XML.

# Custom Response Classes - File, HTML, Redirect, Streaming, etc.

There are several custom response classes you can use to create an instance and return them directly from your *path operations*.

Read more about it in the [FastAPI docs for Custom Response - HTML, Stream, File, others](https://fastapi.tiangolo.com/advanced/custom-response/).

You can import them directly from `fastapi.responses`:

```python
from fastapi.responses import (
    FileResponse,

          call: Call,
          response: Response,
        ) {
          responses.offer(response.body.string())
        }
      }

    // Make the first request waiting until we get our auth challenge.
    val request = Request(server.url("/"))
    blockingAuthClient.newCall(request).enqueue(callback)
    val response1 = responses.take()
    assertThat(response1).isEqualTo("")

        .build()
    val response1 = client.newCall(request).execute()
    response1.body.close()
    assertThat(response1.header("X-Response-ID")).isEqualTo("1")
    val response2 = get(url)
    response2.body.close()
    if (expectCached) {
      assertThat(response2.header("X-Response-ID")).isEqualTo("1")
    } else {
      assertThat(response2.header("X-Response-ID")).isEqualTo("2")
    }
  }

    server.enqueue(MockResponse(body = "response that will never be received"))
    val response = executeSynchronously("/")
    response.assertFailure(
      // JDK 11 response to the FAIL_HANDSHAKE:
      SSLException::class.java,
      // RI response to the FAIL_HANDSHAKE:
      SSLProtocolException::class.java,
      // Android's response to the FAIL_HANDSHAKE:
      SSLHandshakeException::class.java,