*
   * <p><i>Notes:</i> This is an implementation of the algorithm for Lexicographical Permutations
   * Generation, described in Knuth's "The Art of Computer Programming", Volume 4, Chapter 7,
   * Section 7.2.1.2. The iteration order follows the lexicographical order. This means that the
   * first permutation will be in ascending order, and the last will be in descending order.
   *

In the next chapters, I'll give you more **concrete recipes** to deploy FastAPI applications.

But for now, let's check these important **conceptual ideas**. These concepts also apply to any other type of web API. 💡

## Security - HTTPS { #security-https }

In the [previous chapter about HTTPS](https.md) we learned about how HTTPS provides encryption for your API.

   *
   * <p><i>Notes:</i> This is an implementation of the algorithm for Lexicographical Permutations
   * Generation, described in Knuth's "The Art of Computer Programming", Volume 4, Chapter 7,
   * Section 7.2.1.2. The iteration order follows the lexicographical order. This means that the
   * first permutation will be in ascending order, and the last will be in descending order.
   *

This code is something you can actually use in your application, save the password hashes in your database, etc.

We are going to start from where we left in the previous chapter and increment it.

## About JWT { #about-jwt }

JWT means "JSON Web Tokens".

It's a standard to codify a JSON object in a long dense string without spaces. It looks like this:

```

But even if you never use **FastAPI**, you would benefit from learning a bit about them.

/// note

If you are a Python expert, and you already know everything about type hints, skip to the next chapter.

///

## Motivation { #motivation }

Let's start with a simple example:

{* ../../docs_src/python_types/tutorial001_py310.py *}

Calling this program outputs:

```
John Doe
```

    val sequenceOf = listOf(7L, 8L, 9L)
    val adapter = Adapters.INTEGER_AS_LONG.asSequenceOf()
    assertThat(adapter.fromDer(bytes)).isEqualTo(sequenceOf)
    assertThat(adapter.toDer(sequenceOf)).isEqualTo(bytes)
  }

  @Test fun `point with only x set`() {
    val bytes = "3003800109".decodeHex()
    val point = Point(9L, null)
    assertThat(Point.ADAPTER.fromDer(bytes)).isEqualTo(point)

        // will include a tag and length header as a prefix.
        val adapter = chooser(writer.typeHint) as DerAdapter<Any?>?
        when {
          adapter != null -> adapter.toDer(writer, value)
          else -> writer.writeOctetString(value as ByteString)
        }
      }

      override fun fromDer(reader: DerReader): Any? {
        val adapter = chooser(reader.typeHint) as DerAdapter<Any?>?
        return when {

Ce code est utilisable dans votre application, enregistrez les hachages de mots de passe dans votre base de données, etc.

Nous allons repartir d'où nous nous sommes arrêtés dans le chapitre précédent et l'enrichir.

## À propos de JWT { #about-jwt }

JWT signifie « JSON Web Tokens ».

C'est une norme pour coder un objet JSON dans une longue chaîne compacte sans espaces. Cela ressemble à ceci :

```

    } catch (NoSuchMethodException e) {
      return false;
    }
  }

  abstract static class Chopper {

    final Chopper or(Chopper you) {
      Chopper i = this;
      return new Chopper() {
        @Override
        @Nullable String chop(String str) {
          String result = i.chop(str);
          return result != null ? result : you.chop(str);

    }

    @Test
    @DisplayName("Adapter throwing MalformedURLException on all entries")
    void adapterThrowsOnAllEntries() {
        // Setup
        FileEntry entry1 = mock(FileEntry.class);
        FileEntry entry2 = mock(FileEntry.class);

        when(delegate.hasNext()).thenReturn(true, true, false);
        when(delegate.next()).thenReturn(entry1, entry2);

        // Adapter that always throws