Spring security OAuth parsing the response into an object - spring

Question

I'm new to spring.
I have been following http://spring.io/guides/tutorials/spring-boot-oauth2/ using google oauth in place of facebook.
I am able to return the principle as described in the tutorial, which sends to the browser the json returned by the api call and can use this client side.
#RestController
public class UserControllers {
#RequestMapping("/user")
public Principal user(Principal principal) {
return principal;
}
}
But how would I use this data on the server side? Suppose I wanted just to return the email address on the /user route? Or maybe I want to further populate the Principal with information from a database?
Below is the code I use to set up the oauth authentication.
#EnableWebSecurity
#EnableOAuth2Client
public class SecurityConfiguration extends WebSecurityConfigurerAdapter {
#Autowired
OAuth2ClientContext oauth2ClientContext;
#Override
protected void configure(HttpSecurity http) throws Exception {
http .csrf().disable()
.logout().logoutSuccessUrl("/").permitAll() //logout logic handled by spring
.and()
.antMatcher("/**")
.authorizeRequests()
.antMatchers("/", "/login**", "/webjars/**", "/user")
.permitAll()
.anyRequest().authenticated()
.and().exceptionHandling().authenticationEntryPoint(new LoginUrlAuthenticationEntryPoint("/"))
.and()
.addFilterBefore(ssoFilter(), BasicAuthenticationFilter.class);
}
#Bean
public FilterRegistrationBean oauth2ClientFilterRegistration(OAuth2ClientContextFilter filter) {
FilterRegistrationBean registration = new FilterRegistrationBean();
registration.setFilter(filter);
registration.setOrder(-100);
return registration;
}
protected Filter ssoFilter() {
CompositeFilter filter = new CompositeFilter();
List<Filter> filters = new ArrayList<>();
filters.add(constructFilter("/login/google", google(), googleResource()));
filter.setFilters(filters);
return filter;
}
private Filter constructFilter(String endpoint, OAuth2ProtectedResourceDetails clientDetails, ResourceServerProperties resourceDetails) {
OAuth2ClientAuthenticationProcessingFilter filter = new CustomOauth2AuthFilter(endpoint);
OAuth2RestTemplate template = new OAuth2RestTemplate(clientDetails, oauth2ClientContext);
filter.setRestTemplate(template);
filter.setTokenServices(new UserInfoTokenServices(resourceDetails.getUserInfoUri(), clientDetails.getClientId()));
return filter;
}
/*
/Returns a new AuthorizationCodeResourceDetails object configured with the properties from the application.yml file
*/
#Bean
#ConfigurationProperties("google.client")
OAuth2ProtectedResourceDetails google() {
return new AuthorizationCodeResourceDetails();
}
/*
/Returns a new ResourceServerProperties object configured with the properties from the application.yml file
*/
#Bean
#ConfigurationProperties("google.resource")
ResourceServerProperties googleResource() {
return new ResourceServerProperties();
}
}
Thanks in advance,
Dan