如何在單一 FastAPI 端點中處理表單和 JSON 資料？

如何建立可以接受表單或 JSON 正文的 FastAPI 端點？

在 FastAPI 中，您可以建立可以接受表單或 JSON 正文的端點使用不同的方法。以下是一些選項：

選項1：使用依賴函數

此選項涉及建立一個依賴函數，該函數檢查Content-Type 請求標頭的值並使用Starlette 的方法解析正文

<code class="python">from fastapi import FastAPI, Depends, Request
from starlette.datastructures import FormData

app = FastAPI()

async def get_body(request: Request):
    content_type = request.headers.get('Content-Type')
    if content_type is None:
        raise HTTPException(status_code=400, detail='No Content-Type provided!')
    elif content_type == 'application/json':
        return await request.json()
    elif (content_type == 'application/x-www-form-urlencoded' or
          content_type.startswith('multipart/form-data')):
        try:
            return await request.form()
        except Exception:
            raise HTTPException(status_code=400, detail='Invalid Form data')
    else:
        raise HTTPException(status_code=400, detail='Content-Type not supported!')

@app.post('/')
def main(body = Depends(get_body)):
    if isinstance(body, dict):  # if JSON data received
        return body
    elif isinstance(body, FormData):  # if Form/File data received
        msg = body.get('msg')
        items = body.getlist('items')
        return msg</code>

選項2：定義單獨的端點

另一個選項是使用單一端點，並將檔案和/或表單資料參數定義為可選。如果任何參數有值傳遞給它們，則表示請求是 application/x-www-form-urlencoded 或 multipart/form-data。否則，它可能是一個 JSON 請求。

<code class="python">from fastapi import FastAPI, UploadFile, File, Form
from typing import Optional, List

app = FastAPI()

@app.post('/')
async def submit(items: Optional[List[str]] = Form(None),
                    files: Optional[List[UploadFile]] = File(None)):
    # if File(s) and/or form-data were received
    if items or files:
        filenames = None
        if files:
            filenames = [f.filename for f in files]
        return {'File(s)/form-data': {'items': items, 'filenames': filenames}}
    else:  # check if JSON data were received
        data = await request.json()
        return {'JSON': data}</code>

選項3：使用中間件

您也可以使用中間件來檢查傳入請求並將其重新路由到/submitJSON 或/ SubmitForm 端點，具體取決於請求的Content-Type。

<code class="python">from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse

app = FastAPI()

@app.middleware("http")
async def some_middleware(request: Request, call_next):
    if request.url.path == '/':
        content_type = request.headers.get('Content-Type')
        if content_type is None:
            return JSONResponse(
                content={'detail': 'No Content-Type provided!'}, status_code=400)
        elif content_type == 'application/json':
            request.scope['path'] = '/submitJSON'
        elif (content_type == 'application/x-www-form-urlencoded' or
              content_type.startswith('multipart/form-data')):
            request.scope['path'] = '/submitForm'
        else:
            return JSONResponse(
                content={'detail': 'Content-Type not supported!'}, status_code=400)

    return await call_next(request)

@app.post('/')
def main():
    return

@app.post('/submitJSON')
def submit_json(item: Item):
    return item

@app.post('/submitForm')
def submit_form(msg: str = Form(...), items: List[str] = Form(...),
                    files: Optional[List[UploadFile]] = File(None)):
    return msg</code>

測試選項

您可以使用 Python 的 requests 庫測試上述選項：

<code class="python">import requests

url = 'http://127.0.0.1:8000/'
files = [('files', open('a.txt', 'rb')), ('files', open('b.txt', 'rb'))]
payload ={'items': ['foo', 'bar'], 'msg': 'Hello!'}
 
# Send Form data and files
r = requests.post(url, data=payload, files=files)  
print(r.text)

# Send Form data only
r = requests.post(url, data=payload)              
print(r.text)

# Send JSON data
r = requests.post(url, json=payload)              
print(r.text)</code>

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