I have keycloak standalone running on my local machine.
I created new realm called \'spring-test\', then new client called \'login-app\'
According to the rest docu
With Curl
curl -X POST \
http://localhost:8080/auth/realms/api-gateway/protocol/openid-connect/token \
-H 'Accept: */*' \
-H 'Accept-Encoding: gzip, deflate' \
-H 'Cache-Control: no-cache' \
-H 'Connection: keep-alive' \
-H 'Content-Length: 73' \
-H 'Content-Type: application/x-www-form-urlencoded' \
-H 'Cookie: JSESSIONID=F8CD240FF046572F864DC37148E51128.a139df207ece; JSESSIONID=65D31B82F8C5FCAA5B1577DA03B4647C' \
-H 'Host: localhost:8080' \
-H 'Postman-Token: debc4f90-f555-4769-b392-c1130726a027,d5087d9f-9253-48bd-bb71-fda1d4558e4d' \
-H 'User-Agent: PostmanRuntime/7.15.2' \
-H 'cache-control: no-cache' \
-d 'grant_type=password&client_id=api-gateway&username=admin&password=temp123'
By Postman (Select x-www-form-urlencoded option for parameters)