Springboot 2 Oauth2 cannot redirect to SSO client - spring

Question

I'm current working on the implementation of Springboot 2.x oauth2. But I got some tricky problems.
The project comprises both auth-server and sso-client (GitHub link is provided in the bottom). The problem is: when I entered a protected URL (eg localhost:9000/) it will be redirected to the login page configured in the auth-server. However, it won't redirect back to sso-client after successful login.
Authorization server config for auth-server:
#Configuration
#EnableAuthorizationServer
public class AuthorizationServerConfig extends AuthorizationServerConfigurerAdapter {
private AuthenticationManager authenticationManager;
public AuthorizationServerConfig(AuthenticationConfiguration authenticationConfiguration) throws Exception {
this.authenticationManager = authenticationConfiguration.getAuthenticationManager();
}
#Override
public void configure(AuthorizationServerSecurityConfigurer security) throws Exception {
super.configure(security);
}
#Override
public void configure(ClientDetailsServiceConfigurer clients) throws Exception {
clients.inMemory()
.withClient("client")
.secret("secret")
.authorizedGrantTypes("authorization_code")
.scopes("all")
.autoApprove(true);
}
#Override
public void configure(AuthorizationServerEndpointsConfigurer endpoints) throws Exception {
endpoints.authenticationManager(authenticationManager);
}
}
Security config for auth-server:
#Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
#Bean
public PasswordEncoder passwordEncoder() {
return new BCryptPasswordEncoder();
}
#Override
protected void configure(AuthenticationManagerBuilder auth) throws Exception {
auth.inMemoryAuthentication()
.withUser("root")
.password(passwordEncoder().encode("root"))
.roles("ADMIN");
}
#Override
protected void configure(HttpSecurity http) throws Exception {
http.antMatcher("/**")
.authorizeRequests()
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.csrf().disable();
}
}
Security config for sso-client:
#Configuration
#EnableOAuth2Sso
public class SecurityConfig extends WebSecurityConfigurerAdapter {
#Override
protected void configure(HttpSecurity http) throws Exception {
http.antMatcher("/**")
.authorizeRequests()
.anyRequest().authenticated();
}
}
application.yml for sso-client:
auth-server: http://localhost:9090
server:
port: 9000
security:
oauth2:
client:
client-id: client
client-secret: secret
scope: all
user-authorization-uri: ${auth-server}/oauth/authorize
access-token-uri: ${auth-server}/oauth/token
resource:
token-info-uri: ${auth-server}/oauth/check_token
preferTokenInfo: false
Here is the link to this project: https://github.com/paul8263/SpringBoot2Oauth2
PS: I made it work with spring boot 1.5.8: https://github.com/paul8263/SsoDemo2
I compared the codes with Springboot2 (first link) but I barely noticed any obvious difference.
Could someone help me solve this problem by making the simple demo working? Many thanks.