例如，您可以添加一个额外的媒体类型` image/png` ，声明您的路径操作可以返回JSON对象（媒体类型 `application/json` ）或PNG图像：

{* ../../docs_src/additional_responses/tutorial002.py hl[19:24,28] *}

/// note

- 请注意，您必须直接使用 `FileResponse` 返回图像。

///

/// info

- 除非在 `responses` 参数中明确指定不同的媒体类型，否则**FastAPI**将假定响应与主响应类具有相同的媒体类型（默认为` application/json` ）。
- 但是如果您指定了一个自定义响应类，并将 `None `作为其媒体类型，**FastAPI**将使用 `application/json` 作为具有关联模型的任何其他响应。

///

## 组合信息

### Choosing between application and network interceptors

Each interceptor chain has relative merits.

**Application interceptors**

 * Don't need to worry about intermediate responses like redirects and retries.
 * Are always invoked once, even if the HTTP response is served from the cache.

            "content": {
                "application/json": {
                    "schema": {
                        "$ref": "#/components/schemas/Message"
                    }
                }
            }
        },
        "200": {
            "description": "Successful Response",
            "content": {
                "application/json": {
                    "schema": {

<span style="color: green;">INFO</span>:     Started server process [28722]
<span style="color: green;">INFO</span>:     Waiting for application startup.
<span style="color: green;">INFO</span>:     Application startup complete.
```

</div>

/// note

La commande `uvicorn main:app` fait référence à :

* `main` : le fichier `main.py` (le module Python).

import org.apache.maven.api.annotations.Nullable;

/**
 * Represents a hierarchical trace of nested requests within a session, enabling correlation between
 * session events and their originating operations in the application code. The trace structure
 * supports the following key features:
 *
 * <ul>
 *   <li>Maintains parent-child relationships between requests to track operation nesting</li>

        @DisplayName("Should return correct mime type for multiple extensions")
        @CsvSource({ "txt, text/plain", "css, text/css", "js, application/x-javascript", "zip, application/zip", "tar, application/x-tar",
                "gz, application/x-gzip", "tiff, image/tiff", "tif, image/tiff" })
        void testVariousExtensions(String extension, String expectedMimeType) throws IOException {
            assertEquals(expectedMimeType, mimeMap.getMimeType(extension));

## API Request Parameters

### Token

The OAuth 2.0 access token that is provided by the identity provider. Application must get this token by authenticating the application using client credential grants before the application makes an AssumeRoleWithClientGrants call.

| Params               | Value                                          |

Puedes declarar múltiples parámetros `Form` en una *path operation*, pero no puedes también declarar campos `Body` que esperas recibir como JSON, ya que el request tendrá el body codificado usando `application/x-www-form-urlencoded` en lugar de `application/json`.

Esto no es una limitación de **FastAPI**, es parte del protocolo HTTP.

///

## Recapitulación

/// warning

You can declare multiple `Form` parameters in a *path operation*, but you can't also declare `Body` fields that you expect to receive as JSON, as the request will have the body encoded using `application/x-www-form-urlencoded` instead of `application/json`.

This is not a limitation of **FastAPI**, it's part of the HTTP protocol.

///

## Recap { #recap }

        // Then
        assertNotNull(appKey, "Application key should not be null");
        assertEquals(16, appKey.length, "Application key should be 16 bytes");
        assertFalse(Arrays.equals(sessionKey, appKey), "Application key should be different from session key");
    }

    @Test
    @DisplayName("Should derive different application keys for different dialects")