...et **FastAPI** utilise ces mêmes déclarations pour :

* **Définir les prérequis** : depuis les paramètres de chemins des requêtes, les entêtes, les corps, les dépendances, etc.
* **Convertir des données** : depuis la requête vers les types requis.
* **Valider des données** : venant de chaque requête :
    * Générant automatiquement des **erreurs** renvoyées au client quand la donnée est invalide.
* **Documenter** l'API avec OpenAPI :

    // in the opposite order from how they were added so we need to reverse the list to fulfill our
    // contract.
    // This is somewhat annoying, but turns out to be very fast in practice. Alternatively, we could
    // drop the contract on the method that enforces this queue like behavior since depending on it
    // is likely to be a bug anyway.

        assertFalse(entry.isComplete());
        assertTrue(entry.hasChanges());
        assertTrue(entry.getChildren().isEmpty());
    }

    @Test
    public void testExpiration() {
        // Set a very short max age
        entry.setMaxAge(100); // 100ms

        assertFalse(entry.isExpired());
        assertFalse(entry.needsRefresh());

        // Wait for expiration
        try {

{!../../docs_src/bigger_applications/app/main.py!}
```

and it will work correctly, together with all the other *path operations* added with `app.include_router()`.

/// info | Very Technical Details

**Note**: this is a very technical detail that you probably can **just skip**.

---

The `APIRouter`s are not "mounted", they are not isolated from the rest of the application.

  - type: markdown
    attributes:
      value: >
        Comparing two approaches to a use case side by side can make it easier to examine the
        differences between them.


        Additionally, it's very useful to us if you can provide a "straw API" — what the
        method signatures would look like, for example, even if the method and class names are still

  - type: checkboxes
    id: checks
    attributes:
      label: First Check
      description: Please confirm and check all the following options.
      options:
        - label: I added a very descriptive title here.
          required: true
        - label: I used the GitHub search to find a similar question and didn't find it.
          required: true

        Smb2LeaseKey key = leaseManager.requestLease(path, requestedState);
        assertNotNull(leaseManager.getLease(key));

        // Wait a bit and then cleanup with a very short expiration time
        Thread.sleep(10);
        int cleaned = leaseManager.cleanupExpiredLeases(1); // 1ms expiration

        assertEquals(1, cleaned);
        assertNull(leaseManager.getLease(key));
    }

You can also read more about them in the <a href="https://en.wikipedia.org/wiki/Environment_variable" class="external-link" target="_blank">Wikipedia for Environment Variable</a>.

In many cases it's not very obvious how environment variables would be useful and applicable right away. But they keep showing up in many different scenarios when you are developing, so it's good to know about them.

   * thus a motivated caller may be able to expose the reference to another thread that would then
   * call cancel() and be unable to cancel the delegate.
   * There are a number of ways to solve this, none of which are very pretty, and it is currently
   * believed to be a purely theoretical problem (since the other actions should supply sufficient
   * write-barriers).
   */

  @LazyInit private @Nullable ListenableFuture<V> delegateRef;

        assertEquals("short", result);
    }

    @Test
    void testReadStringWithMaxLengthExceeded() {
        smb.useUnicode = false;
        byte[] buffer = "a very long string that exceeds max length".getBytes();
        assertThrows(RuntimeException.class, () -> {
            smb.readString(buffer, 0, 10, false);
        });
    }

    @Test
    void testEncodeDecode() {