}
    return throwable;
  }

  /**
   * Gets a {@code Throwable} cause chain as a list. The first entry in the list will be {@code
   * throwable} followed by its cause hierarchy. Note that this is a snapshot of the cause chain and
   * will not reflect any subsequent changes to the cause chain.
   *
   * <p>Here's an example of how it can be used to find specific types of exceptions in the cause
   * chain:

* 次に、アプリケーションの残りの部分に**リクエスト**を渡して (*path operation* によって) 処理させます。
* 次に、ミドルウェアはアプリケーション (の *path operation*) によって生成された**レスポンス**を受け取ります。
* その**レスポンス**に対して何かを実行したり、必要なコードを実行したりできます。
* そして、**レスポンス**を返します。

/// note | 技術詳細

`yield` を使った依存関係をもつ場合は、終了コードはミドルウェアの *後に* 実行されます。

バックグラウンドタスク ([バックグラウンドタスク](background-tasks.md) セクションで説明します。後で確認できます) がある場合は、それらは全てのミドルウェアの *後に* 実行されます。

///

## ミドルウェアの作成 { #create-a-middleware }

首先，當然你可以自由混用 `Path`、`Query` 與請求 Body 參數的宣告，**FastAPI** 會知道該怎麼做。

你也可以將 Body 參數宣告為可選，方法是將預設值設為 `None`：

{* ../../docs_src/body_multiple_params/tutorial001_an_py310.py hl[18:20] *}

/// note | 注意

請注意，在此情況下，從 body 取得的 `item` 是可選的，因為它的預設值是 `None`。

///

## 多個 Body 參數 { #multiple-body-parameters }

在前一個範例中，路徑操作（path operation）會期望一個包含 `Item` 屬性的 JSON 主體，例如：

```JSON
{
    "name": "Foo",

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the
 * documentation on another copy of this annotation}.
 */

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the
 * documentation on another copy of this annotation}.
 */

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the
 * documentation on another copy of this annotation}.
 */

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

/**
 * Signifies that a test should not be run under Android. This annotation is respected only by our
 * Google-internal Android suite generators. Note that those generators also suppress any test
 * annotated with LargeTest.
 *
 * <p>For more discussion, see {@linkplain com.google.common.base.AndroidIncompatible the
 * documentation on another copy of this annotation}.
 */

import okhttp3.Request;
import okhttp3.Response;
import okhttp3.mockwebserver.MockResponse;
import okhttp3.mockwebserver.MockWebServer;

/**
 * Create UNIX domain sockets for MockWebServer and OkHttp and connect 'em together. Note that we
 * cannot do TLS over domain sockets.
 */
public class ClientAndServer {
  public void run() throws Exception {
    File socketFile = new File("/tmp/ClientAndServer.sock");

`Query`에 동일한 매개변수를 선언할 수 있습니다.

예를 들어, 경로 매개변수 `item_id`에 `title` 메타데이터 값을 선언하려면 다음과 같이 입력할 수 있습니다:

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[10] *}

/// note | 참고

경로 매개변수는 경로의 일부여야 하므로 언제나 필수입니다. `None`으로 선언하거나 기본값을 지정하더라도 아무 영향이 없으며, 항상 필수입니다.

///

## 필요한 대로 매개변수 정렬하기 { #order-the-parameters-as-you-need }

/// tip | 팁

        field = maxRequests
      }
      promoteAndExecute()
    }

  /**
   * The maximum number of requests for each host to execute concurrently. This limits requests by
   * the URL's host name. Note that concurrent requests to a single IP address may still exceed this
   * limit: multiple hostnames may share an IP address or be routed through the same HTTP proxy.
   *