```

////

## 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 == "":

                            "content": {"application/json": {"schema": {}}},
                        },
                        "422": {
                            "description": "Validation Error",
                            "content": {
                                "application/json": {
                                    "schema": {

... 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.

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 {

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 shinsuke
 * @author Keiichi Watanabe
 */

import org.apache.maven.model.root.RootLocator;
import org.apache.maven.model.superpom.DefaultSuperPomProvider;
import org.apache.maven.model.superpom.SuperPomProvider;
import org.apache.maven.model.validation.DefaultModelValidator;
import org.apache.maven.model.validation.ModelValidator;

import static java.util.Objects.requireNonNull;

/**
 * A factory to create model builder instances when no dependency injection is available. Note: This class is

These handlers are in charge of returning the default JSON responses when you `raise` an `HTTPException` and when the request has invalid data.

You can override these exception handlers with your own.

### Override request validation exceptions

When a request contains invalid data, **FastAPI** internally raises a `RequestValidationError`.

And it also includes a default exception handler for it.

    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"