* 它接收你的应用程序的每一个**请求**.
* 然后它可以对这个**请求**做一些事情或者执行任何需要的代码.
* 然后它将**请求**传递给应用程序的其他部分 (通过某种*路径操作*).
* 然后它获取应用程序生产的**响应** (通过某种*路径操作*).
* 它可以对该**响应**做些什么或者执行任何需要的代码.
* 然后它返回这个 **响应**.

/// note | "技术细节"

如果你使用了 `yield` 关键字依赖, 依赖中的退出代码将在执行中间件*后*执行.

如果有任何后台任务(稍后记录), 它们将在执行中间件*后*运行.

///

## 创建中间件

要创建中间件你可以在函数的顶部使用装饰器 `@app.middleware("http")`.

中间件参数接收如下参数:

* `request`.

// UnmarshalXML decodes NoncurrentVersionExpiration
func (n *NoncurrentVersionExpiration) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
	// To handle xml with MaxNoncurrentVersions from older MinIO releases.
	// note: only one of MaxNoncurrentVersions or NewerNoncurrentVersions would be present.
	type noncurrentExpiration struct {
		XMLName                 xml.Name       `xml:"NoncurrentVersionExpiration"`

		return false
	}

	if prefix == "" {
		return true
	}
	if v.ExcludeFolders && strings.HasSuffix(prefix, "/") {
		return false
	}

	for _, sprefix := range v.ExcludedPrefixes {
		// Note: all excluded prefix patterns end with `/` (See Validate)
		sprefix.Prefix += "*"

		if matched := wildcard.MatchSimple(sprefix.Prefix, prefix); matched {
			return false
		}
	}
	return true
}

```

</div>

## In Detail

The marker `@pytest.mark.anyio` tells pytest that this test function should be called asynchronously:

{* ../../docs_src/async_tests/test_main.py hl[7] *}

/// tip

Note that the test function is now `async def` instead of just `def` as before when using the `TestClient`.

///

Then we can create an `AsyncClient` with the app, and send async requests to it, using `await`.

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 * with the License.  You may obtain a copy of the License at
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