val call =
      client.newCall(
        Request(
          url = server.url("/foo"),
          body =
            object : RequestBody() {
              override fun contentType(): MediaType = "text/plain; charset=utf-8".toMediaType()

              override fun writeTo(sink: BufferedSink) {
                sink.write(postBytes)
              }
            },
        ),
      )

```

### `HTMLResponse`

Takes some text or bytes and returns an HTML response, as you read above.

### `PlainTextResponse`

Takes some text or bytes and returns an plain text response.

```Python hl_lines="2  7  9"
{!../../../docs_src/custom_response/tutorial005.py!}
```

### `JSONResponse`

Takes some data and returns an `application/json` encoded response.

instead of being called directly (as it would block the server).

If you are coming from another async framework that does not work in the way described above and you are used to defining trivial compute-only *path operation functions* with plain `def` for a tiny performance gain (about 100 nanoseconds), please note that in **FastAPI** the effect would be quite opposite. In these cases, it's better to use `async def` unless your *path operation functions* use code that performs blocking <abbr...

=== "Python 3.8+"

    ```Python hl_lines="1  20"
    {!> ../../../docs_src/extra_models/tutorial004.py!}
    ```

## Response with arbitrary `dict`

You can also declare a response using a plain arbitrary `dict`, declaring just the type of the keys and values, without using a Pydantic model.

This is useful if you don't know the valid field/attribute names (that would be needed for a Pydantic model) beforehand.

Do mesmo modo, você pode sobreescrever o `HTTPException`.

Por exemplo, você pode querer retornar uma *response* em *plain text* ao invés de um JSON para os seguintes erros:

```Python hl_lines="3-4  9-11  22"
{!../../../docs_src/handling_errors/tutorial004.py!}
```

!!! note "Detalhes Técnicos"

/plugins/kapt3/kapt3-compiler/tests-gen/ "Kotlin Compiler Core" "Kotlin JVM"
/plugins/kapt4/ "Kotlin JVM"
/plugins/kotlinx-serialization/ Sergey.Shanshin Leonid.Startsev
/plugins/js-plain-objects/ Artem.Kobzar
/libraries/tools/js-plain-objects Artem.Kobzar
/plugins/lombok/ "Kotlin Compiler Core"
/plugins/noarg/ "Kotlin Compiler Core"
/plugins/parcelize/ "Kotlin Compiler Core"

            .header("Content-Type", "text/plain-ish")
            .build(),
        )
      }
    server.enqueue(MockResponse())
    client.newCall(
      request()
        .post("Hi?".toRequestBody(PLAIN))
        .build(),
    ).execute()
    applicationLogs
      .assertLogEqual("--> POST $url")
      .assertLogEqual("Content-Type: text/plain; charset=utf-8")
      .assertLogEqual("Content-Length: 3")

    assertFailsWith<IllegalArgumentException> {
      Request.Builder().method("GET", "abc".toRequestBody("text/plain".toMediaType()))
    }
  }

  @Test
  fun head() {
    server.enqueue(
      MockResponse(
        headers = headersOf("Content-Type", "text/plain"),
      ),
    )
    val request =
      Request.Builder()
        .url(server.url("/"))
        .head()

       *
       * Example:
       * ```
       * --> POST /greeting http/1.1
       * Host: example.com
       * Content-Type: plain/text
       * Content-Length: 3
       * --> END POST
       *
       * <-- 200 OK (22ms)
       * Content-Type: plain/text
       * Content-Length: 6
       * <-- END HTTP
       * ```
       */
      HEADERS,

      /**

    subgraph Client Node
        Client
        CZ["Ztunnel"]
    end
    subgraph Server Node
        Server
        SZ["Ztunnel"]
    end
    Client--Plain-->CZ
    CZ-."HBONE (target)".->Server
    CZ--"HBONE (actual)"-->SZ
    SZ--Plain-->Server
```

### Pooling

User connections can be multiplexed over shared HBONE connections.
This is done through standard HTTP/2 pooling.