Met **FastAPI** declareer je parameters met type hints en krijg je:

* **Editor ondersteuning**.
* **Type checks**.

...en **FastAPI** gebruikt dezelfde declaraties om:

* **Vereisten te definïeren **: van request pad parameters, query parameters, headers, bodies, dependencies, enz.
* **Data te converteren**: van de request naar het vereiste type.

 *
 */
@Deprecated
public interface ConflictResolver {
    String ROLE = ConflictResolver.class.getName();

    /**
     * Determines which of the specified versions of an artifact to use when there are conflicting declarations.
     *
     * @param node1 the first artifact declaration
     * @param node2 the second artifact declaration

```JSON
{"item_id":3}
```

/// check

Notice that the value your function received (and returned) is `3`, as a Python `int`, not a string `"3"`.

So, with that type declaration, **FastAPI** gives you automatic request <abbr title="converting the string that comes from an HTTP request into Python data">"parsing"</abbr>.

///

## Data validation { #data-validation }

## Mélanger les paramètres `Path`, `Query` et body

Tout d'abord, sachez que vous pouvez mélanger les déclarations des paramètres `Path`, `Query` et body, **FastAPI** saura quoi faire.

Vous pouvez également déclarer des paramètres body comme étant optionnels, en leur assignant une valeur par défaut à `None` :

   */
  private final @Nullable Object annotatedType;

  Parameter(
      Invokable<?, ?> declaration,
      int position,
      TypeToken<?> type,
      Annotation[] annotations,
      @Nullable Object annotatedType) {
    this.declaration = declaration;
    this.position = position;
    this.type = type;
    this.annotations = ImmutableList.copyOf(annotations);

Déclarez ensuite votre modèle de données en tant que classe qui hérite de `BaseModel`.

Utilisez les types Python standard pour tous les attributs :

{* ../../docs_src/body/tutorial001.py hl[7:11] *}

import javax.inject.Named;
import javax.inject.Singleton;

import org.apache.maven.artifact.resolver.ResolutionNode;

/**
 * Resolves conflicting artifacts by always selecting the farthest declaration. Farthest is defined as the
 * declaration that has the most transitive steps away from the project being built.
 *
 * @since 3.0
 */
@Named("farthest")
@Singleton
@Deprecated

   * explicit {@code @NullableDecl} annotation (see <a
   * href="https://github.com/google/guava/issues/1819">#1819</a>).
   *
   * <p>It is not necessary to consider visibility, return type, or type parameter declarations. The
   * declaration of a method with the same name and formal parameters as {@link Object#equals} that
   * is not public and boolean-returning, or that declares any type parameters, would be rejected at
   * compile-time.
   */

import org.apache.maven.artifact.versioning.OverConstrainedVersionException;

/**
 * Resolves conflicting artifacts by always selecting the newest declaration. Newest is defined as the
 * declaration whose version is greater according to <code>ArtifactVersion.compareTo</code>.
 *
 * @see ArtifactVersion#compareTo
 * @since 3.0
 */
@Named("newest")
@Singleton
@Deprecated

```Python
my_list: list[str]
```

In versions of Python before 3.9, it would be:

```Python
from typing import List

my_list: List[str]
```

That's all standard Python syntax for type declarations.

Use that same standard syntax for model attributes with internal types.

So, in our example, we can make `tags` be specifically a "list of strings":