## Các dependency tùy chọn

Sử dụng bởi Pydantic:

* <a href="https://github.com/JoshData/python-email-validator" target="_blank"><code>email-validator</code></a> - cho email validation.

Sử dụng Starlette:

* <a href="https://www.python-httpx.org" target="_blank"><code>httpx</code></a> - Bắt buộc nếu bạn muốn sử dụng `TestClient`.

/** File generated by Grunt -- do not modify
 *  JQUERY-FORM-VALIDATOR
 *
 *  @version 2.3.77
 *  @website http://formvalidator.net/
 *  @author Victor Jonsson, http://victorjonsson.se
 *  @license MIT
 */

Це можна досягти за допомогою <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-after-validator" class="external-link" target="_blank">Pydantic's `AfterValidator`</a> в середині `Annotated`.

/// tip | Підказка

Pydantic також має <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-before-validator" class="external-link" target="_blank">`BeforeValidator`</a> та інші. 🤓

///

    * Vous pouvez avoir des objets **JSON fortement imbriqués** tout en ayant, pour chacun, de la validation et des annotations.
* **Renouvelable**:
    * Pydantic permet de définir de nouveaux types de données ou vous pouvez étendre la validation avec des méthodes sur un modèle décoré avec le<abbr title="en anglais: validator decorator"> décorateur de validation</abbr>

* Validate **complex structures**:
    * Use of hierarchical Pydantic models, Python `typing`’s `List` and `Dict`, etc.
    * And validators allow complex data schemas to be clearly and easily defined, checked and documented as JSON Schema.
    * You can have deeply **nested JSON** objects and have them all validated and annotated.
* **Extensible**:

errors.header = <ul class="has-error">
errors.footer = </ul>
errors.prefix = <li><i class="fa fa-exclamation-circle"></i>
errors.suffix = </li>
# ----------------------------------------------------------
# Javax Validator
# ---------------
constraints.AssertFalse.message = {item}는 false여야 합니다.
constraints.AssertTrue.message = {item}는 true여야 합니다.
constraints.DecimalMax.message = {item}는 {value}보다 작아야 합니다.

Maar standaard werkt alles **“gewoon”**.

### Validatie

* Validatie voor de meeste (of misschien wel alle?) Python **datatypes**, inclusief:
    * JSON objecten (`dict`).
    * JSON array (`list`) die itemtypes definiëren.
    * String (`str`) velden, die min en max lengtes hebben.
    * Getallen (`int`, `float`) met min en max waarden, enz.

* Validatie voor meer exotische typen, zoals:
    * URL.
    * E-mail.

    private final AtomicLong integerOverflowsPrevented = new AtomicLong(0);

    /**
     * Validate SMB response buffer bounds
     *
     * @param buffer the buffer to validate
     * @param expectedSize expected minimum size
     * @param maxSize maximum allowed size
     * @throws SmbException if validation fails
     */
    public void validateBuffer(byte[] buffer, int expectedSize, int maxSize) throws SmbException {

        }
        developers {
          developer {
            name.set("Square, Inc.")
          }
        }
      }
    }
  }

  plugins.withId("binary-compatibility-validator") {
    configure<ApiValidationExtension> {
      ignoredPackages += "okhttp3.logging.internal"
      ignoredPackages += "mockwebserver3.internal"
      ignoredPackages += "okhttp3.internal"

    * Swagger UI.
    * ReDoc.

---

Voltando ao código do exemplo anterior, **FastAPI** irá:

* Validar que existe um `item_id` na rota para requisições `GET` e `PUT`.
* Validar que `item_id` é do tipo `int` para requisições `GET` e `PUT`.
    * Se não é validado, o cliente verá um útil, claro erro.