## 使用回调的应用

示例如下。

假设要开发一个创建发票的应用。

发票包括 `id`、`title`（可选）、`customer`、`total` 等属性。

API 的用户 （外部开发者）要在您的 API 内使用 POST 请求创建一条发票记录。

（假设）您的 API 将：

* 把发票发送至外部开发者的消费者
* 归集现金
* 把通知发送至 API 的用户（外部开发者）
    * 通过（从您的 API）发送 POST 请求至外部 API （即**回调**）来完成

## 常规 **FastAPI** 应用

添加回调前，首先看下常规 API 应用是什么样子。

常规 API 应用包含接收 `Invoice` 请求体的*路径操作*，还有包含回调 URL 的查询参数 `callback_url`。

* `@app.get()`
* `@app.post()`
* `@app.put()`
* `@app.delete()`
* etc.

{* ../../docs_src/response_status_code/tutorial001_py39.py hl[6] *}

/// note | Nota

Observe que `status_code` é um parâmetro do método "decorador" (`get`, `post`, etc). Não da sua função de *operação de rota*, como todos os parâmetros e corpo.

///

	// The same context must be provided when the generated key
	// should be decrypted. Therefore, it is the callers
	// responsibility to remember the corresponding context for
	// a particular DEK. The context may be nil.
	GenerateKey(context.Context, *GenerateKeyRequest) (DEK, error)

	// DecryptKey decrypts the ciphertext with the key referenced
	// by the key ID. The context must match the context value

		return l, nil
	}

	// Set ServerName in TLS config for proper certificate validation
	host, _, err := net.SplitHostPort(ldapServer)
	if err != nil {
		host = ldapServer
	}

	l.LDAP = ldap.Config{
		ServerAddr:    ldapServer,
		SRVRecordName: getCfgVal(SRVRecordName),
		TLS: &tls.Config{
			ServerName:         host,
			MinVersion:         tls.VersionTLS12,
			NextProtos:         []string{"h2", "http/1.1"},

 * Language.
 * <p>
 * This extensible enum has two defined values, {@link #NONE} and {@link #JAVA_FAMILY},
 * but can be extended by registering a {@code org.apache.maven.api.spi.LanguageProvider}.
 * <p>
 * Implementation must have {@code equals()} and {@code hashCode()} implemented, so implementations of this interface
 * can be used as keys.
 *
 * @since 4.0.0
 */
@Experimental
@Immutable
@SuppressWarnings("checkstyle:InterfaceIsType")

{* ../../docs_src/advanced_middleware/tutorial001_py39.py hl[2,6] *}

## `TrustedHostMiddleware` { #trustedhostmiddleware }

Erzwingt, dass alle eingehenden Requests einen korrekt gesetzten `Host`-Header haben, um sich vor HTTP-Host-Header-Angriffen zu schützen.

{* ../../docs_src/advanced_middleware/tutorial002_py39.py hl[2,6:8] *}

Die folgenden Argumente werden unterstützt:

* `@app.get()`
* `@app.post()`
* `@app.put()`
* `@app.delete()`
* etc.

{* ../../docs_src/response_status_code/tutorial001_py39.py hl[6] *}

/// note | Nota

Observa que `status_code` es un parámetro del método "decorador" (`get`, `post`, etc). No de tu *path operation function*, como todos los parámetros y body.

///

        raise HTTPException(status_code=400, detail="Invalid X-Token header")
    if item_id not in fake_db:
        raise HTTPException(status_code=404, detail="Item not found")
    return fake_db[item_id]


@app.post("/items/", response_model=Item)
async def create_item(item: Item, x_token: Annotated[str, Header()]):
    if x_token != fake_secret_token:
        raise HTTPException(status_code=400, detail="Invalid X-Token header")

// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package init

import "os"

func init() {
	// All MinIO operations must be under UTC.
	os.Setenv("TZ", "UTC")

* <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/X-Forwarded-Host" class="external-link" target="_blank">X-Forwarded-Host</a>

///

### Включить пересылаемые заголовки прокси { #enable-proxy-forwarded-headers }