## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

To disable this behavior, use `(SingleHandler).WithSharedResponse()` to disable it.

## Streaming Requests

Streams consists of an initial request with payload and allows for full two-way communication between the client and server.

The handler function has this signature.

Sample handler:
```go

  "Statement": [
    {
      "Action": [
        "admin:CreateUser",
        "admin:DeleteUser",
        "admin:ConfigUpdate"
      ],
      "Effect": "Allow",
      "Sid": ""
    },
    {
      "Action": [
        "s3:*"
      ],
      "Effect": "Allow",
      "Resource": [
        "arn:aws:s3:::*"
      ],
      "Sid": ""
    }
  ]
}
EOF
```

      return Maps.transformValues(
          fromTable.columnMap(), column -> Maps.transformValues(column, function));
    }
  }

  /**
   * Returns an unmodifiable view of the specified table. This method allows modules to provide
   * users with "read-only" access to internal tables. Query operations on the returned table "read
   * through" to the specified table, and attempts to modify the returned table, whether direct or

Let's look at how we can make that work.

## pytest.mark.anyio { #pytest-mark-anyio }

If we want to call asynchronous functions in our tests, our test functions have to be asynchronous. AnyIO provides a neat plugin for this, that allows us to specify that some test functions are to be called asynchronously.

## HTTPX { #httpx }

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

     * index. This constructor is optimized so that it starts at either the head or the tail,
     * depending on which is closer to the specified index. This allows adds to the tail to be done
     * in constant time.
     *
     * @throws IndexOutOfBoundsException if index is invalid
     */
    ValueForKeyIterator(@ParametricNullness K key, int index) {

* kubectl exec now allows using resource name (e.g., deployment/mydeployment) to select a matching pod. ([#73664](https://github.com/kubernetes/kubernetes/pull/73664), [@prksu](https://github.com/prksu))
    * kubectl exec now allows using --pod-running-timeout flag to wait till at least one pod is running.

 * the client is Microsoft Internet Explorer.
 */

/**
 * A servlet that provides network browsing capabilities for SMB shares using SMB1 protocol.
 * This servlet allows users to browse SMB network resources through a web interface.
 */
public class NetworkExplorer extends HttpServlet {

    /**
     * Default constructor.
     */
    public NetworkExplorer() {
        super();

# Größere Anwendungen – mehrere Dateien { #bigger-applications-multiple-files }

Wenn Sie eine Anwendung oder eine Web-API erstellen, ist es selten der Fall, dass Sie alles in einer einzigen Datei unterbringen können.

**FastAPI** bietet ein praktisches Werkzeug zur Strukturierung Ihrer Anwendung bei gleichzeitiger Wahrung der Flexibilität.

/// info | Info

Wenn Sie von Flask kommen, wäre dies das Äquivalent zu Flasks Blueprints.

///

///

### 启用代理转发的请求头 { #enable-proxy-forwarded-headers }

你可以用 *CLI 选项* `--forwarded-allow-ips` 启动 FastAPI CLI，并传入应该被信任、允许读取这些转发请求头的 IP 地址列表。

如果设置为 `--forwarded-allow-ips="*"`，就会信任所有来源 IP。

如果你的**服务器**位于受信任的**代理**之后，并且只有代理会与它通信，这将使其接受该**代理**的任何 IP。

<div class="termy">

```console
$ fastapi run --forwarded-allow-ips="*"