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.

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`

    ```

## Recap

With `Query`, `Path` (and others you haven't seen yet) you can declare metadata and string validations in the same ways as with [Query Parameters and String Validations](query-params-str-validations.md){.internal-link target=_blank}.

And you can also declare numeric validations:

* `gt`: `g`reater `t`han
* `ge`: `g`reater than or `e`qual
* `lt`: `l`ess `t`han
* `le`: `l`ess than or `e`qual

So, even with the code above that doesn't use Pydantic explicitly, FastAPI is using Pydantic to convert those standard dataclasses to Pydantic's own flavor of dataclasses.

And of course, it supports the same:

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

!!! info

    override fun getName(): String =
        delegate.name

    override fun file(path: Any): File =
        delegate.file(path)

    override fun file(path: Any, validation: PathValidation): File =
        delegate.file(path, validation)

    override fun findProject(path: String): Project? =
        delegate.findProject(path)

    override fun getPlugins(): PluginContainer =
        delegate.plugins

            dependencies {
                implementation(kotlin("stdlib"))
            }

            ${if (kotlinVersion >= VersionNumber.parse("1.9.0")) {
                """
                // Work around JVM validation issue: https://youtrack.jetbrains.com/issue/KT-66919
                tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {

@file:Suppress("UnstableApiUsage")

import com.diffplug.gradle.spotless.SpotlessExtension
import com.vanniktech.maven.publish.MavenPublishBaseExtension
import com.vanniktech.maven.publish.SonatypeHost
import java.net.URI
import kotlinx.validation.ApiValidationExtension
import org.gradle.api.tasks.testing.logging.TestExceptionFormat
import org.jetbrains.dokka.gradle.DokkaTaskPartial
import org.jetbrains.kotlin.gradle.dsl.kotlinExtension

                    "schema": {
                        "$ref": "#/components/schemas/Item"
                    }
                }
            }
        },
        "422": {
            "description": "Validation Error",
            "content": {
                "application/json": {
                    "schema": {
                        "$ref": "#/components/schemas/HTTPValidationError"
                    }
                }

        internalReporter.create {
            id(
                "configuration-cache-" + DeprecationMessageBuilder.createDefaultDeprecationId(message),
                message,
                GradleCoreProblemGroup.validation()
            )
            contextualLabel(message)
            documentOfProblem(problem)
            locationOfProblem(problem)
            severity(severity.toProblemSeverity())

                    "schema": {
                        "$ref": "#/components/schemas/Item"
                    }
                }
            }
        },
        "422": {
            "description": "Validation Error",
            "content": {
                "application/json": {
                    "schema": {
                        "$ref": "#/components/schemas/HTTPValidationError"
                    }
                }