# Background Tasks { #background-tasks }

You can define background tasks to be run *after* returning a response.

This is useful for operations that need to happen after a request, but that the client doesn't really have to be waiting for the operation to complete before receiving the response.

This includes, for example:

* Email notifications sent after performing an action:

abstract class WebSocketListener {
  /**
   * Invoked when a web socket has been accepted by the remote peer and may begin transmitting
   * messages.
   */
  open fun onOpen(
    webSocket: WebSocket,
    response: Response,
  ) {
  }

  /** Invoked when a text (type `0x1`) message has been received. */
  open fun onMessage(
    webSocket: WebSocket,
    text: String,
  ) {
  }

/**
 * SMB2 Lock response message. This response acknowledges the successful
 * acquisition or release of byte-range locks.
 *
 * @author mbechler
 *
 */
public class Smb2LockResponse extends ServerMessageBlock2Response {

    /**
     * Constructs an SMB2 lock response with the given configuration.
     *
     * @param config the configuration for this response
     */

        list.setTook(response.getTook().getMillis());
        list.setTotalShards(response.getTotalShards());
        list.setSuccessfulShards(response.getSuccessfulShards());
        list.setFailedShards(response.getFailedShards());
        list.setTotalHits(searchHits.getTotalHits());

        list.setAggregation(response.getAggregations());

        // #pending others

   *
   * ### Duplex Transmission
   *
   * With regular HTTP calls the request always completes sending before the response may begin
   * receiving. With duplex the request and response may be interleaved! That is, request body bytes
   * may be sent after response headers or body bytes have been received.
   *
   * Though any call may be initiated as a duplex call, only web servers that are specially

        "404": {
            "description": "Additional Response",
            "content": {
                "application/json": {
                    "schema": {
                        "$ref": "#/components/schemas/Message"
                    }
                }
            }
        },
        "200": {
            "description": "Successful Response",
            "content": {
                "application/json": {

import org.codelibs.fess.util.RenderDataUtil;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;
import org.lastaflute.web.ruts.process.ActionRuntime;

import jakarta.annotation.Resource;

/**
 * Admin action for Web Config management.
 *
 */

        .build()
    val response = client.newCall(request).execute()
    assertThat(response.body.string()).isEqualTo("A")
    assertThat(response.header("Warning")).isEqualTo(
      "110 HttpURLConnection \"Response is stale\"",
    )
  }

  @Test
  fun requestMaxStaleDirectiveWithNoValue() {
    // Add a stale response to the cache.
    server.enqueue(
      MockResponse

import org.codelibs.fess.opensearch.client.SearchEngineClient;
import org.codelibs.fess.thumbnail.ThumbnailManager;
import org.codelibs.fess.util.ComponentUtil;
import org.lastaflute.web.Execute;
import org.lastaflute.web.response.JsonResponse;
import org.opensearch.action.bulk.BulkResponse;

import jakarta.annotation.Resource;

/**
 * API action for admin document management.

* Uma função `call_next` que receberá o `request` como um parâmetro.
    * Esta função passará a `request` para a *operação de rota* correspondente.
    * Então ela retorna a `response` gerada pela *operação de rota* correspondente.
* Você pode então modificar ainda mais o `response` antes de retorná-lo.

{* ../../docs_src/middleware/tutorial001.py hl[8:9,11,14] *}

/// tip | Dica