# Tarefas em segundo plano { #background-tasks }

Você pode definir tarefas em segundo plano para serem executadas *após* retornar uma resposta.

Isso é útil para operações que precisam acontecer após uma request, mas que o cliente não precisa realmente esperar a operação terminar antes de receber a resposta.

Isso inclui, por exemplo:

* Notificações por e-mail enviadas após realizar uma ação:

import java.security.cert.X509Certificate
import javax.net.ssl.SSLPeerUnverifiedException
import javax.net.ssl.SSLSession
import okhttp3.internal.toImmutableList

/**
 * A record of a TLS handshake. For HTTPS clients, the client is *local* and the remote server is
 * its *peer*.
 *
 * This value object describes a completed handshake. Use [ConnectionSpec] to set policy for new
 * handshakes.
 */
class Handshake internal constructor(

                     * connected. Bastards! Disconnect this tree
                     * so that it reconnects cleanly should the share
                     * reappear in this client's lifetime.
                     */
                    treeDisconnect(true);
                }
                throw se;
            }
        }
    }

### Required, can be `None` { #required-can-be-none }

You can declare that a parameter can accept `None`, but that it's still required. This would force clients to send a value, even if the value is `None`.

To do that, you can declare that `None` is a valid type but simply do not declare a default value:

            } else {

                /* On NT without Unicode the fileNameLength
                 * includes the '\0' whereas on win98 it doesn't. I
                 * guess most clients only support non-unicode so
                 * they don't run into this.
                 */

                /* UPDATE: Maybe not! Could this be a Unicode alignment issue. I hope

<img src="/img/tutorial/websockets/image05.png">

## Обработка отключений и работа с несколькими клиентами { #handling-disconnections-and-multiple-clients }

Если веб-сокет соединение закрыто, то `await websocket.receive_text()` вызовет исключение `WebSocketDisconnect`, которое можно поймать и обработать как в этом примере:

## Recapitulação { #recap }

Agora você pode obter o usuário atual diretamente na sua *função de operação de rota*.

Já estamos na metade do caminho.

Só precisamos adicionar uma *operação de rota* para que o usuário/cliente realmente envie o `username` e `password`.

            doColumn("_id");
        }

        public void columnAccessType() {
            doColumn("accessType");
        }

        public void columnClientIp() {
            doColumn("clientIp");
        }

        public void columnHitCount() {
            doColumn("hitCount");
        }

        public void columnHitCountRelation() {
            doColumn("hitCountRelation");
        }

 * Provides common functionality for handling initialization parameters,
 * content length checks, and default method implementations.
 * It defines the basic structure and configuration options for crawler clients.
 */
public abstract class AbstractCrawlerClient implements CrawlerClient {

    private static final Logger logger = LogManager.getLogger(AbstractCrawlerClient.class);

/// tip | Tipp

Bedenken Sie, dass JSON nur `str` als Schlüssel unterstützt.

Aber Pydantic hat automatische Datenkonvertierung.

Das bedeutet, dass Ihre API-Clients nur Strings senden können, aber solange diese Strings nur Zahlen enthalten, wird Pydantic sie konvertieren und validieren.

Und das `dict`, welches Sie als `weights` erhalten, wird `int`-Schlüssel und `float`-Werte haben.