"anyOf": [{"type": "string"}, {"type": "null"}],
                            },
                            "customer": {"title": "Customer", "type": "string"},
                            "total": {"title": "Total", "type": "number"},
                        },
                    },
                    "InvoiceEvent": {
                        "title": "InvoiceEvent",

                            "anyOf": [{"type": "string"}, {"type": "null"}],
                        },
                        "customer": {"title": "Customer", "type": "string"},
                        "total": {"title": "Total", "type": "number"},
                    },
                },
                "InvoiceEvent": {
                    "title": "InvoiceEvent",
                    "required": ["description", "paid"],

	AmzServerSideEncryptionCustomerAlgorithm     = AmzServerSideEncryption + "-Customer-Algorithm"
	AmzServerSideEncryptionCustomerKey           = AmzServerSideEncryption + "-Customer-Key"
	AmzServerSideEncryptionCustomerKeyMD5        = AmzServerSideEncryption + "-Customer-Key-Md5"
	AmzServerSideEncryptionCopyCustomerAlgorithm = "X-Amz-Copy-Source-Server-Side-Encryption-Customer-Algorithm"

src_obj1_etag=$(echo "${stat_out1}" | jq '.etag')
src_obj1_size=$(echo "${stat_out1}" | jq '.size')
src_obj1_md5=$(echo "${stat_out1}" | jq '.metadata."X-Amz-Server-Side-Encryption-Customer-Key-Md5"')
echo "Stat minio1/test-bucket/defpartsize"
./mc stat --no-list minio1/test-bucket/defpartsize --enc-c "minio1/test-bucket/defpartsize=${TEST_MINIO_ENC_KEY}" --insecure --json

src_obj1_etag=$(echo "${stat_out1}" | jq '.etag')
src_obj1_size=$(echo "${stat_out1}" | jq '.size')
src_obj1_md5=$(echo "${stat_out1}" | jq '.metadata."X-Amz-Server-Side-Encryption-Customer-Key-Md5"')
echo "Stat minio1/test-bucket/defpartsize"
./mc stat --no-list minio1/test-bucket/defpartsize --enc-c "minio1/test-bucket/defpartsize=${TEST_MINIO_ENC_KEY}" --insecure --json

	ErrMissingCustomerKey = Errorf("The SSE-C request is missing the customer key")

	// ErrMissingCustomerKeyMD5 indicates that the HTTP headers contains no SSE-C client key
	// MD5 checksum.
	ErrMissingCustomerKeyMD5 = Errorf("The SSE-C request is missing the customer key MD5")

	// ErrInvalidCustomerKey indicates that the SSE-C client key is not valid - e.g. not a

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

Then your API will (let's imagine):

* Send the invoice to some customer of the external developer.
* Collect the money.
* Send a notification back to the API user (the external developer).

from typing import Union

from fastapi import APIRouter, FastAPI
from pydantic import BaseModel, HttpUrl

app = FastAPI()


class Invoice(BaseModel):
    id: str
    title: Union[str, None] = None
    customer: str
    total: float


class InvoiceEvent(BaseModel):
    description: str
    paid: bool


class InvoiceEventReceived(BaseModel):
    ok: bool


invoices_callback_router = APIRouter()

from fastapi import APIRouter, FastAPI
from pydantic import BaseModel, HttpUrl

app = FastAPI()


class Invoice(BaseModel):
    id: str
    title: str | None = None
    customer: str
    total: float


class InvoiceEvent(BaseModel):
    description: str
    paid: bool


class InvoiceEventReceived(BaseModel):
    ok: bool


invoices_callback_router = APIRouter()


@invoices_callback_router.post(

API 应用调用外部 API 时的流程叫做**回调**。因为外部开发者编写的软件发送请求至您的 API，然后您的 API 要进行回调，并把请求发送至外部 API。

此时，我们需要存档外部 API 的*信息*，比如应该有哪些*路径操作*，返回什么样的请求体，应该返回哪种响应等。

## 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