Es ist so konzipiert, dass es über Funktionen verfügt, welche zwei Parameter empfangen, einen „Request“ und eine „Response“. Dann „lesen“ Sie Teile des Requests und „schreiben“ Teile der Response. Aufgrund dieses Designs ist es nicht möglich, Request-Parameter und -Bodys mit Standard-Python-Typhinweisen als Funktionsparameter zu deklarieren.

```txt
Hello, World from Flask!
```

And if you go to <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a> you will see the response from FastAPI:

```JSON
{
    "message": "Hello World"
}

    Request request = new Request.Builder()
        .url("https://publicobject.com/robots.txt")
        .build();

    try (Response response = client.newCall(request).execute()) {
      if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

      for (Certificate certificate : response.handshake().peerCertificates()) {
        System.out.println(CertificatePinner.pin(certificate));
      }
    }
  }

```txt
Hello, World from Flask!
```

Und wenn Sie auf <a href="http://localhost:8000/v2" class="external-link" target="_blank">http://localhost:8000/v2</a> gehen, sehen Sie die Response von FastAPI:

```JSON
{
    "message": "Hello World"
}

        final HtmlResponse response = HtmlResponse.fromForwardPath("/");
        assertEquals(response, systemHelper.getRedirectResponseToLogin(response));
    }

    public void test_getRedirectResponseToRoot() {
        final HtmlResponse response = HtmlResponse.fromForwardPath("/");
        assertEquals(response, systemHelper.getRedirectResponseToRoot(response));
    }

    public void test_getLogLevel() {

        .header("Host", "cloudflare-dns.com")
        .build()
    client.newCall(request).execute().use { response ->
      assertThat(response.code).isEqualTo(200)
      assertThat(response.protocol).isEqualTo(Protocol.HTTP_2)

      assertThat(response.body.string()).contains("h=cloudflare-dns.com")
    }
  }

  @Test
  fun getWithDns() {
    client =
      client.newBuilder()

///

### Before and after the `response`

You can add code to be run with the `request`,  before any *path operation* receives it.

And also after the `response` is generated, before returning it.

For example, you could add a custom header `X-Process-Time` containing the time in seconds that it took to process the request and generate a response:

```Python hl_lines="10  12-13"

        .url("https://api.github.com/gists/c2a7c39532239ff261be")
        .build();
    try (Response response = client.newCall(request).execute()) {
      if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);

      Gist gist = gistJsonAdapter.fromJson(response.body().source());

      for (Map.Entry<String, GistFile> entry : gist.files.entrySet()) {

from fastapi import FastAPI, Response

app = FastAPI()


@app.get("/headers-and-object/")
def get_headers(response: Response):
    response.headers["X-Cat-Dog"] = "alone in the world"

/// note | "Technical Details"

You could also use `from starlette.responses import HTMLResponse`.

**FastAPI** provides the same `starlette.responses` as `fastapi.responses` just as a convenience for you, the developer. But most of the available responses come directly from Starlette.

///

### Multiple File Uploads with Additional Metadata