}

    public void test_logout_withNullUser() {
        // Setup
        authenticator.setLogoutUrl("https://example.com/logout");

        // Execute
        String result = authenticator.logout(null);

        // Verify
        assertNotNull(result);
        assertEquals("https://example.com/logout", result);
        assertNull(authenticator.getLastLogoutUser());
    }

In this example, when the client requests an item by an ID that doesn't exist, raise an exception with a status code of `404`:

{* ../../docs_src/handling_errors/tutorial001.py hl[11] *}

### The resulting response { #the-resulting-response }

would be valid to use as a **FastAPI** dependency.

In fact, FastAPI uses those two decorators internally.

///

## A database dependency with `yield` { #a-database-dependency-with-yield }

For example, you could use this to create a database session and close it after finishing.

Only the code prior to and including the `yield` statement is executed before creating a response:

You also define in some way at which **moments** your app will send those requests or events.

And **your users** define in some way (for example in a web dashboard somewhere) the **URL** where your app should send those requests.

But you can return a `JSONResponse` directly from your *path operations*.

It might be useful, for example, to return custom headers or cookies.

## Return a `Response` { #return-a-response }

In fact, you can return any `Response` or any sub-class of it.

/// tip

`JSONResponse` itself is a sub-class of `Response`.

Pero en algunos casos necesitas devolver un código de estado diferente al predeterminado.

## Caso de uso

Por ejemplo, imagina que quieres devolver un código de estado HTTP de "OK" `200` por defecto.

Pero si los datos no existieran, quieres crearlos y devolver un código de estado HTTP de "CREATED" `201`.

# Query Parameters and String Validations { #query-parameters-and-string-validations }

**FastAPI** allows you to declare additional information and validation for your parameters.

Let's take this application as example:

{* ../../docs_src/query_params_str_validations/tutorial001_py310.py hl[7] *}

certs-dir: '/home/user/.minio/certs/'
pools: # Specify the nodes and drives with pools
  -
        - 'https://server-example-pool1:9000/mnt/disk{1...4}/'
        - 'https://server1-pool1:9000/mnt/disk{1...4}/'
        - 'https://server3-pool1:9000/mnt/disk{1...4}/'
        - 'https://server4-pool1:9000/mnt/disk{1...4}/'
  -
        - 'https://server-example-pool2:9000/mnt/disk{1...4}/'
        - 'https://server1-pool2:9000/mnt/disk{1...4}/'

{* ../../docs_src/path_params/tutorial001.py hl[6:7] *}

La valeur du paramètre `item_id` sera transmise à la fonction dans l'argument `item_id`.

Donc, si vous exécutez cet exemple et allez sur <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>,
vous verrez comme réponse :

```JSON
{"item_id":"foo"}
```

 * it returns a ByteArrayInputStream.
 *
 * <p>Example usage:
 * <pre>
 * {@code
 * // In-memory caching
 * byte[] data = "example data".getBytes();
 * try (ContentCache cache = new ContentCache(data)) {
 *     InputStream inputStream = cache.getInputStream();
 *     // Read from inputStream
 * }
 *
 * // File-based caching
 * File file = new File("example.txt");
 * try (ContentCache cache = new ContentCache(file)) {