"error": "invalid_grant", "error_description": "Bad credentials"

Question

I'm implementing Oauth2 in SpringBoot RestFul API. Everything is working fine except when I use the wrong password getting error response:

Status : 400Bad Request

{
    "error": "invalid_grant",
    "error_description": "Bad credentials"
}

But I'm excepting like this:

Status : 401 Unauthorized

{
    "error": "unauthorized",
    "error_description": "Invalid username/password combination"
}

After wrong password:

Answer 1

A 401 status would be returned if your authorization credentials are incorrect. This would be your basic auth username and password (in Postman Authorization tab), which appears were unchanged.

A 400 status is returned because the validation of the request's body parameters (username, password) fails to find a match. (ie. Bad credentials were supplied.) It's like other requests where a required parameter is not submitted or formatted correctly. Your request passes the oauth server's basic authorization for the login endpoint. It would be confusing and incorrect if both scenarios returned a 401 status.400 status