Minimum spring boot configuration for OAuth2 server and client - spring-oauth2

Question

I tried to code a 'Hello world' type of exercise to learn Spring Boot support for OAuth2, and the minimum required configuration.
Components:
Authorization server
webapp, which will call the auth server to authenticate the user, and will greet him
Expected flow:
I open the webapp
I get redirected to auth server
I login to auth server
I approve the requested scope
I get redirected back to webapp
I see a greeting (webapp should fetch my username from auth server)
The last point fails with 401:Could not obtain access token.
Last redirect link is http://localhost:9001/ui/login?code=wcXMG4&state=JEEYqC
Am I too naive to assume that the below code&configuration should suffice for my expected flow?
Auth server:
#SpringBootApplication
#EnableAuthorizationServer
#EnableResourceServer
#RestController
public class AuthServer {
public static void main(String[] args) {
SpringApplication.run(AuthServer.class);
}
#GetMapping("/whois")
Principal whois(Principal principal) {
return principal;
}
}
Auth server properties:
server.port=9000
server.contextPath=/sso
security.user.name=joe
security.user.password=password
security.oauth2.client.clientId=SOMEAPP
security.oauth2.client.clientSecret=SECRET
security.oauth2.client.authorized-grant-types=authorization_code,refresh_token,password
security.oauth2.client.scope=read
security.oauth2.resource.userInfoUri=http://localhost:9000/sso/whois
Webapp:
#SpringBootApplication
#EnableOAuth2Sso
#RestController
public class UiServer {
public static void main(String[] args) {
SpringApplication.run(UiServer.class);
}
#GetMapping("/")
String helloWorld(Principal principal) {
return "Yay, auth server provided identity, you are " + principal;
}
}
Webapp properties:
server.port=9001
server.contextPath=/ui
security.oauth2.client.client-id=SOMEAPP
security.oauth2.client.client-secret=SECRET
security.oauth2.client.accessTokenUri=http://localhost:9000/sso/oauth/access_token
security.oauth2.client.userAuthorizationUri=http://localhost:9000/sso/oauth/authorize
security.oauth2.resource.user-info-uri=http://localhost:9000/sso/whois

Answer 1

After spinning up with debug on, it turns out that security.oauth2.client.accessTokenUri is incorrect.
The right endpoint is not .../oauth/access_token, but .../oauth/token.
Probably the tutorial I was looking at used outdated uri.
With that fix, this minimum config does what's expected of it, so I'll close the question.
The real fun begins when you try to customize it, bypassing the defaults; to me it seems that spring oauth still has major bugs, and requires hacky/unexpected approach to work around them in few use cases.