from typing import Annotated

from fastapi import FastAPI, Form
from pydantic import BaseModel

app = FastAPI()


class FormData(BaseModel):
    username: str
    password: str


@app.post("/login/")
async def login(data: Annotated[FormData, Form()]):

///

## 什么是 「表单数据」

与 JSON 不同，HTML 表单（`<form></form>`）向服务器发送数据通常使用「特殊」的编码。

**FastAPI** 要确保从正确的位置读取数据，而不是读取 JSON。

/// note | "技术细节"

不包含文件时，表单数据一般用 `application/x-www-form-urlencoded`「媒体类型」编码。

但表单包含文件时，编码为 `multipart/form-data`。使用了 `File`，**FastAPI** 就知道要从请求体的正确位置获取文件。

from fastapi import FastAPI, Form
from pydantic import BaseModel
from typing_extensions import Annotated

app = FastAPI()


class FormData(BaseModel):
    username: str
    password: str

    class Config:
        extra = "forbid"


@app.post("/login/")
async def login(data: Annotated[FormData, Form()]):

x;-ms-flex-wrap:wrap;flex-wrap:wrap;margin-right:-5px;margin-left:-5px}.form-row>.col,.form-row>[class*=col-]{padding-right:5px;padding-left:5px}.form-check{position:relative;display:block;padding-left:1.25rem}.form-check-input{position:absolute;margin-top:.3rem;margin-left:-1.25rem}.form-check-input:disabled~.form-check-label,.form-check-input[disabled]~.form-check-label{color:#6c757d}.form-check-label{margin-bottom:0}.form-check-inline{display:-ms-inline-flexbox;display:inline-flex;-ms-flex-al...

                                    <la:errors/>
                                </div>
                                <div class="form-group row">
                                    <label for="protwordsFile" class="col-sm-3 text-sm-right col-form-label"><la:message
                                            key="labels.dict_protwords_file"/></label>
                                    <div class="col-sm-9">

                                    <la:errors/>
                                </div>
                                <div class="form-group row">
                                    <label for="synonymFile" class="col-sm-3 text-sm-right col-form-label"><la:message
                                            key="labels.dict_synonym_file"/></label>
                                    <div class="col-sm-9">

							<div class="card-body">
								<div class="form-group row">
									<label for="targetVersion" class="col-sm-3 text-sm-right col-form-label"><la:message
											key="labels.target_version"
										/></label>
									<div class="col-sm-9">
										<la:errors property="targetVersion" />
										<la:select styleId="targetVersion" property="targetVersion" styleClass="form-control">
											<la:option value="13.0">13.0</la:option>

@needs_py39
def test_get_root(app: FastAPI):
    client = TestClient(app)
    response = client.get("/")
    assert response.status_code == 200, response.text
    assert b"<form" in response.content


@needs_py39
def test_openapi_schema(client: TestClient):
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text
    assert response.json() == {

        form.dictId = dictId;
        validateApi(form, messages -> {});
        final StopwordsFile file = stopwordsService.getStopwordsFile(form.dictId).orElseGet(() -> {
            throwValidationErrorApi(messages -> messages.addErrorsFailedToUploadStopwordsFile(GLOBAL));
            return null;
        });
        try (InputStream inputStream = form.stopwordsFile.getInputStream()) {

///

## Was sind „Formulardaten“

HTML-Formulare (`<form></form>`) senden die Daten in einer „speziellen“ Kodierung zum Server, welche sich von JSON unterscheidet.

**FastAPI** stellt sicher, dass diese Daten korrekt ausgelesen werden, statt JSON zu erwarten.