* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.
* Then it passes the **request** to be processed by the rest of the application (by some *path operation*).

{* ../../docs_src/security/tutorial002_an_py310.py hl[30:32] *}

## Recap { #recap }

You can now get the current user directly in your *path operation function*.

We are already halfway there.

We just need to add a *path operation* for the user/client to actually send the `username` and `password`.

     * @param b second operand
     * @param operation the operation name
     * @throws ArithmeticException if operation would overflow
     */
    public static void validateIntegerAddition(int a, int b, String operation) {
        long result = (long) a + (long) b;
        if (result > Integer.MAX_VALUE || result < Integer.MIN_VALUE) {
            throw new ArithmeticException(operation + " would cause integer overflow: " + a + " + " + b);

{* ../../docs_src/security/tutorial002_an_py310.py hl[30:32] *}

## Resumen

Ahora puedes obtener el usuario actual directamente en tu *path operation function*.

Ya estamos a mitad de camino.

Solo necesitamos agregar una *path operation* para que el usuario/cliente envíe realmente el `username` y `password`.

But you can also declare the `Response` that you want to be used (e.g. any `Response` subclass), in the *path operation decorator* using the `response_class` parameter.

The contents that you return from your *path operation function* will be put inside of that `Response`.

Por ejemplo, cuando usas GraphQL normalmente realizas todas las acciones usando solo operaciones `POST`.

///

### Paso 4: define la **path operation function**

Esta es nuestra "**path operation function**":

* **path**: es `/`.
* **operation**: es `get`.
* **function**: es la función debajo del "decorador" (debajo de `@app.get("/")`).

{* ../../docs_src/first_steps/tutorial001.py hl[7] *}

    }

    /**
     * Returns a {@link CopyOptions} with the specified property names to include in the operation.
     *
     * @param propertyNames
     *            An array of property names. Must not be {@literal null} or an empty array.
     * @return A {@link CopyOptions} with the specified property names to include in the operation.
     * @see CopyOptions#include(CharSequence...)
     */

/// tip

Note that, much like [dependencies in *path operation decorators*](dependencies/dependencies-in-path-operation-decorators.md){.internal-link target=_blank}, no value will be passed to your *path operation function*.

///

The end result is that the item paths are now:

* `/items/`
* `/items/{item_id}`

...as we intended.

```mermaid
sequenceDiagram

participant client as Client
participant handler as Exception handler
participant dep as Dep with yield
participant operation as Path Operation
participant tasks as Background tasks

    Note over client,operation: Puede lanzar excepciones, incluyendo HTTPException
    client ->> dep: Iniciar request
    Note over dep: Ejecutar código hasta yield
    opt raise Exception

      // the operation would be a no-op, so exceptions are allowed but not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(absent = SUPPORTS_PUT)
  public void testReplaceEntry_unsupportedAbsentKey() {
    try {
      getMap().replace(k3(), v3(), v4());
    } catch (UnsupportedOperationException tolerated) {