Log OAuth calls made by the webclient library - spring

Question

I have an application that uses microservice architecture and services are protected by Spring OAuth2 Client Credentials Grant type. We use spring WebClient to call from one service to another along with Spring OAuth client library as it handles fetching OAuth credentials transparently.
As we know the Spring (OAuth client) makes a call to Authorization server to request a new token from Auth server when it doesn't have a token or the current token is expired. How can we log a statement on client side whenever Spring (OAuth client) makes a call to the OAuth server? We would like to log this statement to see how frequently the OAuth client library is making calls to the Authorization Server.
public WebClient webClient()
{
return WebClient.builder()
.apply(filter())
.baseUrl("http://localhost:8082/resource")
.build();
}
public Consumer<Builder> filter()
{
ServletOAuth2AuthorizedClientExchangeFilterFunction oAuth =
new ServletOAuth2AuthorizedClientExchangeFilterFunction(authorizedClientManager);
oAuth.setDefaultClientRegistrationId("my-client");
return oAuth.oauth2Configuration();
}

Answer 1

Define a custom token client that logs when sending a token request to the authorization server.
#Slf4j
public class LoggingClientCredentialsTokenResponseClient
implements OAuth2AccessTokenResponseClient<OAuth2ClientCredentialsGrantRequest> {
private DefaultClientCredentialsTokenResponseClient delegate =
new DefaultClientCredentialsTokenResponseClient();
#Override
public OAuth2AccessTokenResponse getTokenResponse(
OAuth2ClientCredentialsGrantRequest clientCredentialsGrantRequest) {
log.debug("Sending request {}", clientCredentialsGrantRequest);
var response = delegate.getTokenResponse(clientCredentialsGrantRequest);
log.debug("Received response {}", response);
return response;
}
}
Create an authorized client manager that uses the custom token client.
#Bean
public OAuth2AuthorizedClientManager authorizedClientManager(
ClientRegistrationRepository clientRegistrationRepository,
OAuth2AuthorizedClientService authorizedClientService) {
var authorizedClientProvider = OAuth2AuthorizedClientProviderBuilder.builder()
.clientCredentials(builder ->
builder.accessTokenResponseClient(
new LoggingClientCredentialsTokenResponseClient()))
.build();
var authorizedClientManager =
new AuthorizedClientServiceOAuth2AuthorizedClientManager(
clientRegistrationRepository, authorizedClientService);
authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
return authorizedClientManager;
}
Create a WebClient that uses the authorized client manager.
#Bean
public WebClient oauth2WebClient(
WebClient.Builder webClientBuilder,
OAuth2AuthorizedClientManager authorizedClientManager) {
var oauth2Filter =
new ServletOAuth2AuthorizedClientExchangeFilterFunction(authorizedClientManager);
oauth2Filter.setDefaultClientRegistrationId("my-client");
return webClientBuilder.apply(oauth2Filter.oauth2Configuration())
.baseUrl("http://localhost:8082/resource")
.build();
}