import static java.lang.annotation.ElementType.CONSTRUCTOR;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import jakarta.validation.Constraint;

# Response-Header { #response-headers }

## Einen `Response`-Parameter verwenden { #use-a-response-parameter }

Sie können einen Parameter vom Typ `Response` in Ihrer *Pfadoperation-Funktion* deklarieren (wie Sie es auch für Cookies tun können).

Und dann können Sie Header in diesem *vorübergehenden* <abbr title="Response – Antwort: Daten, die der Server zum anfragenden Client zurücksendet">Response</abbr>-Objekt festlegen.

    }
  }

  /*
   * Preconditions.checkNotNull is *intended* for performing eager null checks on parameters that a
   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past

## Usando `BackgroundTasks` { #using-backgroundtasks }

Primero, importa `BackgroundTasks` y define un parámetro en tu *path operation function* con una declaración de tipo de `BackgroundTasks`:

{* ../../docs_src/background_tasks/tutorial001_py310.py hl[1,13] *}

**FastAPI** creará el objeto de tipo `BackgroundTasks` por ti y lo pasará como ese parámetro.

## Crear una función de tarea { #create-a-task-function }

But this guide shows you, more or less, how they are intended to be used.

///

### Using Pydantic's `exclude_unset` parameter { #using-pydantics-exclude-unset-parameter }

If you want to receive partial updates, it's very useful to use the parameter `exclude_unset` in Pydantic's model's `.model_dump()`.

Like `item.model_dump(exclude_unset=True)`.

        buffer[37] = 0x00;
        buffer[38] = 0x00;

        // Parameter count (2 bytes)
        buffer[39] = 0x00;
        buffer[40] = 0x00;

        // Parameter offset (2 bytes)
        buffer[41] = 0x00;
        buffer[42] = 0x00;

        // Parameter displacement (2 bytes)
        buffer[43] = 0x00;
        buffer[44] = 0x00;

        // Data count (2 bytes)

    /** Highlight query parameters. */
    public String[] hq;

    /** Search query parameter for error page. */
    public String q;

    /** Number of results parameter for error page. */
    public String num;

    /** Sort parameter for error page. */
    public String sort;

    /** Language parameter for error page. */
    public String lang;

    /** Additional fields map for cache operations. */

# Cookie Parameter Models { #cookie-parameter-models }

If you have a group of **cookies** that are related, you can create a **Pydantic model** to declare them. 🍪

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

/// tip

     * Applies the specified character encoding to decode parameter values.
     *
     * @param request the HTTP request containing the query string
     * @param enc the character encoding to use for decoding
     * @return a map of parameter names to their decoded values
     * @throws IOException if an error occurs during parameter parsing
     */

    @UriType(protocolType = ProtocolType.WEB)
    public String testMethod() {
        return "http://example.com";
    }

    // Test parameter with UriType annotation
    public void testMethodWithParameter(@UriType(protocolType = ProtocolType.FILE) final String uri) {
        // Method for testing parameter annotation
    }

    // Test groups for validation
    private interface TestGroup {
    }