# Header Parameter Models

If you have a group of related **header parameters**, 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`. 🤓

///

## Header Parameters with a Pydantic Model

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

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

// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package lifecycle

import (
	"encoding/xml"
	"fmt"
	"testing"
)

// appropriate errors on validation
func TestInvalidExpiration(t *testing.T) {
	testCases := []struct {
		inputXML    string
		expectedErr error
	}{
		{ // Expiration with zero days
			inputXML: ` <Expiration>

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

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
 */
public class AdminDictStemmeroverrideAction extends FessAdminAction {

set FESS_JAVA_OPTS=%FESS_JAVA_OPTS% -Dlog4j2.disable.jmx=true
set FESS_JAVA_OPTS=%FESS_JAVA_OPTS% -Dlog4j2.formatMsgNoLookups=true
set FESS_JAVA_OPTS=%FESS_JAVA_OPTS% -Dlog4j.skipJansi=true

REM SSL truststore for certificate validation over https
REM FESS_JAVA_OPTS=%FESS_JAVA_OPTS% -Djavax.net.ssl.trustStore=/tech/elastic/config/truststore.jks
REM FESS_JAVA_OPTS=%FESS_JAVA_OPTS% -Djavax.net.ssl.trustStorePassword=changeit

It won't do any data conversion with Pydantic models, it won't convert the contents to any type, etc.

This gives you a lot of flexibility. You can return any data type, override any data declaration or validation, etc.

## Using the `jsonable_encoder` in a `Response`

Because **FastAPI** doesn't make any changes to a `Response` you return, you have to make sure its contents are ready for it.

package lifecycle

import (
	"encoding/xml"
	"fmt"
	"testing"
)

// TestInvalidRules checks if Rule xml with invalid elements returns
// appropriate errors on validation
func TestInvalidRules(t *testing.T) {
	invalidTestCases := []struct {
		inputXML    string
		expectedErr error
	}{
		{ // Rule with ID longer than 255 characters
			inputXML: ` <Rule>

With `Form` you can declare the same configurations as with `Body` (and `Query`, `Path`, `Cookie`), including validation, examples, an alias (e.g. `user-name` instead of `username`), etc.

/// info

`Form` is a class that inherits directly from `Body`.

///

/// tip