Python FastApi error 422 (Unprocessable Entity)

Question

When I use a POST request to send form data from a JS script running on port 5500 using XMLHttpRequest to my backend which is a FastAPI app running on port 8000, I am always met with this error Unprocessable Entity. Here is the server-side:

origins = ["https://localhost:5500"]
app.add_middleware(
    CORSMiddleware,
    allow_origins=origins,
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)


@app.post("/test")
def test(username: str = Form(...)):
    print(f"########### Received {username} #############")

And here is the client-side code:

async function sendData() {
    formData = new FormData();
    formData.append('username', 'Kareem');
    const response = await fetch('http://localhost:8000/test', {
        method: 'POST',
        data: formData
    })
}

I tried your code in my server. It is working fine. I think their ia configuration error in backend or problem in frontend. Did you tested the api in swgger or other tools? — Mahir Mahbub
– Mahir Mahbub, Commented Nov 17, 2020 at 11:53
@Mause Response {type: "cors", url: "localhost:8000/test", redirected: false, status: 422, ok: false, …} body: (...) bodyUsed: false headers: Headers {} ok: false redirected: false status: 422 statusText: "Unprocessable Entity" type: "cors" url: "localhost:8000/test" proto: Response — Kareem Amr
– Kareem Amr, Commented Nov 17, 2020 at 11:54

ukibbb · Accepted Answer · 2021-04-27 17:27:16Z

0

Hi I had a same problem . I used URLSearchParams.

This is my code

let urlencoded = new URLSearchParams();
urlencoded.append("username", username);
urlencoded.append("password", password);


try {
    setLoading(true);
    const response =  await fetch("http://127.0.0.1:5000/login", {
        method: 'POST',
        headers: {
             "Content-Type" : "application/x-www-form-urlencoded"
        },
        body: urlencoded,
        redirect: 'follow'

    })

answered Apr 27, 2021 at 17:27

ukibbb

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WhooNo Over a year ago

Could you explain a little bit why? The code snippet is throwing an error so it's hard to understand in context.

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