// Test with property that doesn't exist and default value
        cmdList.clear();
        execJob.testAddSystemProperty(cmdList, "non.existent.property", "default.value", null);
        assertEquals(1, cmdList.size());
        assertEquals("-Dnon.existent.property=default.value", cmdList.get(0));

        // Test with property that doesn't exist and no default value
        cmdList.clear();

# Templates { #templates }

Você pode usar qualquer template engine com o **FastAPI**.

Uma escolha comum é o Jinja2, o mesmo usado pelo Flask e outras ferramentas.

Existem utilitários para configurá-lo facilmente que você pode usar diretamente em sua aplicação **FastAPI** (fornecidos pelo Starlette).

## Instalar dependências { #install-dependencies }

Certifique-se de criar um [ambiente virtual](../virtual-environments.md), ativá-lo e instalar `jinja2`:

map[desc:CMYK colors:[cyan magenta yellow black]]
```

likewise, increasing depth level to `3` yields:
```
red
green
blue
cyan
magenta
yellow
black
```

optionally, kev:value pairs can be emitted as an individual struct:
```go
decoder := jstream.NewDecoder(f, 2).EmitKV() // enable KV streaming at a depth level of 2
```

```
jstream.KV{desc RGB}
jstream.KV{colors [red green blue]}
jstream.KV{desc CMYK}

package org.codelibs.core.beans.util;

import java.util.LinkedHashMap;

import org.codelibs.core.exception.IllegalKeyOfBeanMapException;

/**
 * A map with String keys that throws an exception when accessing (get) a non-existent key.
 *
 * @author higa
 */
public class BeanMap extends LinkedHashMap<String, Object> {

    private static final long serialVersionUID = 1;

    /**
     * Creates a new {@link BeanMap}.
     */

//     it defaults to defaultTTL.
//
// This function defines an onEvicted callback that is invoked when a cache entry is evicted.
// The callback ensures that if the evicted value (v) is not nil, its Close method is called asynchronously
// to release associated resources.
//
// Returns:

## Autres middlewares { #other-middlewares }

Il existe de nombreux autres middlewares ASGI.

Par exemple :

- [Le `ProxyHeadersMiddleware` d'Uvicorn](https://github.com/encode/uvicorn/blob/master/uvicorn/middleware/proxy_headers.py)

    assert response.status_code == 401, response.text
    assert response.json() == {"detail": "Not authenticated"}


def test_incorrect_token():
    response = client.get("/items", headers={"Authorization": "Non-existent testtoken"})
    assert response.status_code == 401, response.text
    assert response.json() == {"detail": "Not authenticated"}


def test_token():

    // of the values gets evicted. With weak keys, we use identity equality, which means using
    // System.identityHashCode, which means the assignment of keys to segments is nondeterministic,
    // so more than (maximumSize / #segments) keys could get assigned to the same segment, which
    // would cause one to be evicted.
    return new CacheBuilderFactory()

Grâce à cela, **FastAPI** fournit lui-même une documentation d'API alternative (utilisant ReDoc), accessible sur [http://127.0.0.1:8000/redoc](http://127.0.0.1:8000/redoc) :

<img src="/img/tutorial/path-params/image02.png">

# Étendre OpenAPI { #extending-openapi }

Il existe des cas où vous pouvez avoir besoin de modifier le schéma OpenAPI généré.

Dans cette section, vous verrez comment faire.

## Le processus normal { #the-normal-process }

Le processus normal (par défaut) est le suivant.

Une application (instance) `FastAPI` a une méthode `.openapi()` censée retourner le schéma OpenAPI.