... et avec cette déclaration unique, vous obtenez :

* Une assistance dans votre IDE, notamment :
    * la complétion.
    * la vérification des types.
* La validation des données :
    * des erreurs automatiques et claires lorsque les données ne sont pas valides.
    * une validation même pour les objets <abbr title="JavaScript Object Notation">JSON</abbr> profondément imbriqués.

    def __init__(self, errors: Sequence[Any], *, body: Any = None) -> None:
        super().__init__(errors)
        self.body = body

    def __str__(self) -> str:
        message = f"{len(self._errors)} validation errors:\n"
        for err in self._errors:
            message += f"  {err}\n"

```Python
item: Item
```

...and with that single declaration you get:

* Editor support, including:
    * Completion.
    * Type checks.
* Validation of data:
    * Automatic and clear errors when the data is invalid.
    * Validation even for deeply nested JSON objects.

	}

	n = len(b0) - len(b)
	switch {
	case err == ErrWriteTooLong:
		return n, errMissData // Not possible; implies bug in validation logic
	case err != nil:
		return n, err
	case sw.logicalRemaining() == 0 && sw.physicalRemaining() > 0:
		return n, errUnrefData // Not possible; implies bug in validation logic
	case overwrite:
		return n, ErrWriteTooLong
	default:
		return n, nil
	}
}

```

////

## Declare `Header` parameters

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

You can define the default value as well as all the extra validation or annotation parameters:

//// tab | Python 3.10+

```Python hl_lines="9"
{!> ../../docs_src/header_params/tutorial001_an_py310.py!}
```

////

//// tab | Python 3.9+

```Python hl_lines="9"

}

func newWarmBackendS3(conf madmin.TierS3, tier string) (*warmBackendS3, error) {
	u, err := url.Parse(conf.Endpoint)
	if err != nil {
		return nil, err
	}

	// Validation code
	switch {
	case conf.AWSRoleWebIdentityTokenFile == "" && conf.AWSRoleARN != "" || conf.AWSRoleWebIdentityTokenFile != "" && conf.AWSRoleARN == "":

import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.login.exception.LoginFailureException;
import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.validation.VaErrorHook;

import jakarta.annotation.Resource;
import jakarta.servlet.http.HttpSession;

public class LoginAction extends FessLoginAction {

Cela vous donne beaucoup de flexibilité. Vous pouvez retourner n'importe quel type de données, surcharger n'importe quelle déclaration ou validation de données.

## Utiliser le `jsonable_encoder` dans une `Response`

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 org.lastaflute.web.validation.VaMessenger;
import org.opensearch.index.query.QueryBuilder;
import org.opensearch.index.query.QueryBuilders;

import jakarta.annotation.Resource;
import jakarta.servlet.http.HttpServletRequest;

/**

import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;
import org.lastaflute.web.ruts.process.ActionRuntime;
import org.lastaflute.web.validation.VaErrorHook;
import org.lastaflute.web.validation.exception.ValidationErrorException;

import jakarta.annotation.Resource;

/**
 * @author nullpos
 * @author ma2tani
 */
public class AdminDictMappingAction extends FessAdminAction {