```Python hl_lines="2  10"
{!../../../docs_src/custom_response/tutorial009.py!}
```

You can also use the `response_class` parameter:

```Python hl_lines="2  8  10"
{!../../../docs_src/custom_response/tutorial009b.py!}
```

In this case, you can return the file path directly from your *path operation* function.

## Custom response class

### Custom Generate Unique ID Function

FastAPI uses a **unique ID** for each *path operation*, it is used for the **operation ID** and also for the names of any needed custom models, for requests or responses.

You can customize that function. It takes an `APIRoute` and outputs a string.

Код выхода в зависимостях с `yield` выполняется *после* отправки ответа, поэтому [Обработчик исключений](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank} уже будет запущен. В коде выхода (после `yield`) нет ничего, перехватывающего исключения, брошенные вашими зависимостями.

        "//tensorflow/core:test_main",
        "@com_google_absl//absl/strings",
    ],
)

cc_library(
    name = "custom_device_testutil",
    testonly = True,
    srcs = ["custom_device_testutil.cc"],
    hdrs = ["custom_device_testutil.h"],
    visibility = ["//tensorflow:internal"],
    deps = [
        ":c_api",
        ":c_api_experimental",
        ":c_api_test_util",

const val pluginPortalUrlOverride = "-Dorg.gradle.internal.plugins.portal.url.override=%gradle.plugins.portal.url%"

fun BuildSteps.customGradle(init: GradleBuildStep.() -> Unit, custom: GradleBuildStep.() -> Unit): GradleBuildStep =
    GradleBuildStep(init)
        .apply(custom)
        .also {
            step(it)
        }

/**
 * Adds a [Gradle build step](https://confluence.jetbrains.com/display/TCDL/Gradle)

We see that we are going to need some dependencies used in several places of the application.

So we put them in their own `dependencies` module (`app/dependencies.py`).

We will now use a simple dependency to read a custom `X-Token` header:

=== "Python 3.9+"

    ```Python hl_lines="3  6-8" title="app/dependencies.py"
    {!> ../../../docs_src/bigger_applications/app_an_py39/dependencies.py!}
    ```

=== "Python 3.8+"

//
// This API can be used to request client certificates to authenticate to kube-apiserver
// (with the "kubernetes.io/kube-apiserver-client" signerName),
// or to obtain certificates from custom non-Kubernetes signers.
message CertificateSigningRequest {
  // +optional
  optional k8s.io.apimachinery.pkg.apis.meta.v1.ObjectMeta metadata = 1;

  // spec contains the certificate request, and is immutable after creation.

## 使用 `yield` 和 `HTTPException` 的依赖项

您看到可以使用带有 `yield` 的依赖项，并且具有捕获异常的 `try` 块。

在 `yield` 后抛出 `HTTPException` 或类似的异常是很诱人的，但是**这不起作用**。

带有`yield`的依赖中的退出代码在响应发送之后执行，因此[异常处理程序](../handling-errors.md#install-custom-exception-handlers){.internal-link target=_blank}已经运行过。没有任何东西可以捕获退出代码（在`yield`之后）中的依赖抛出的异常。

所以，如果在`yield`之后抛出`HTTPException`，默认（或任何自定义）异常处理程序捕获`HTTPException`并返回HTTP 400响应的机制将不再能够捕获该异常。

!!! tip
    You could use the same technique to extend the JSON Schema and add your own custom extra info.

    For example you could use it to add metadata for a frontend user interface, etc.

!!! info

It used custom types in its declarations instead of standard Python types, but it was still a huge step forward.

It also was one of the first frameworks to generate a custom schema declaring the whole API in JSON.