root = root.toLowerCase();

                /* The link entries contain maps of referrals by path representing DFS links.
                 * Note that paths are relative to the root like "\" and not "\example.com\root".
                 */
                CacheEntry links = (CacheEntry) roots.get(root);
                if (links != null && now > links.expiration) {
                    roots.remove(root);

* Enforce security, authentication, role requirements, etc.
* And many other things...

All these, while minimizing code repetition.

## First Steps { #first-steps }

Let's see a very simple example. It will be so simple that it is not very useful, for now.

But this way we can focus on how the **Dependency Injection** system works.

### Create a dependency, or "dependable" { #create-a-dependency-or-dependable }

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

The value of the path parameter `item_id` will be passed to your function as the argument `item_id`.

So, if you run this example and go to <a href="http://127.0.0.1:8000/items/foo" class="external-link" target="_blank">http://127.0.0.1:8000/items/foo</a>, you will see a response of:

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

### El response resultante

Si el cliente solicita `http://example.com/items/foo` (un `item_id` `"foo"`), ese cliente recibirá un código de estado HTTP de 200, y un response JSON de:

```JSON
{
  "item": "The Foo Wrestlers"
}
```

### A response resultante


Se o cliente faz uma requisição para `http://example.com/items/foo` (um `item_id` `"foo"`), esse cliente receberá um HTTP status code 200, e uma resposta JSON:


```
{
  "item": "The Foo Wrestlers"
}
```

///

### DNS

Ahora centrémonos en todas las partes realmente de HTTPS.

Primero, el navegador consultaría con los **servidores DNS** cuál es la **IP del dominio**, en este caso, `someapp.example.com`.

Los servidores DNS le dirían al navegador que use una **dirección IP** específica. Esa sería la dirección IP pública utilizada por tu servidor, que configuraste en los servidores DNS.

        private final int dataCompactionMode = 1;
        private final int dataLength = 1024;
        private final int dataOffset = 54;

        @BeforeEach
        public void setUp() {
            // Build a sample buffer
            int bufferIndex = 0;
            bufferIndex += 2; // reserved
            writeInt2(dataCompactionMode, buffer, bufferIndex);
            bufferIndex += 2;
            bufferIndex += 2; // reserved

        final Map<String, Object> doc = new HashMap<>();
        final String keyProp = NAME_PREFIX + id;
        doc.put(KEY_PROPERTY, keyProp);
        doc.put("url", "http://example.com/" + id);
        doc.put("boost", id);
        doc.put("role", "Rguest");
        requestBody.put("doc", doc);
        return requestBody;
    }

    @Override

 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingDeque} forward <b>indiscriminately</b> to the
 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
 * behavior of {@link #offer} which can lead to unexpected behavior. In this case, you should
 * override {@code offer} as well.
 *

        assertEquals("", key);
    }

    public void test_getHostKey_withVirtualHost() {
        RelatedContent entity = createRelatedContent("term", "content", "example.com");
        String key = relatedContentHelper.getHostKey(entity);
        assertEquals("example.com", key);
    }

    public void test_getRelatedContents_noMatch() {
        List<RelatedContent> testData = new ArrayList<>();