Updates tokenrelay.adoc for MVC

Author: spencergibb

docs/modules/ROOT/pages/spring-cloud-gateway-server-mvc/filters/tokenrelay.adoc

@@ -6,7 +6,9 @@ forwards the incoming token to outgoing resource requests. The
 consumer can be a pure Client (like an SSO application) or a Resource
 Server.
 
-Spring Cloud Gateway can forward OAuth2 access tokens downstream to the services
+////
+TODO: support TokenRelay clientRegistrationId
+Spring Cloud Gateway Server MVC can forward OAuth2 access tokens downstream to the services
 it is proxying using the `TokenRelay` filter.
 
 The `TokenRelay` filter takes one optional parameter, `clientRegistrationId`.
@@ -44,21 +46,28 @@ spring:
 ----
 
 The example above specifies a `clientRegistrationId`, which can be used to obtain and forward an OAuth2 access token for any available `ClientRegistration`.
+////
 
-Spring Cloud Gateway can also forward the OAuth2 access token of the currently authenticated user `oauth2Login()` is used to authenticate the user.
-To add this functionality to the gateway, you can omit the `clientRegistrationId` parameter like this:
+Spring Cloud Gateway Server MVC can forward the OAuth2 access token of the currently authenticated user `oauth2Login()` is used to authenticate the user.
+//To add this functionality to the gateway, you can omit the `clientRegistrationId` parameter like this:
 
-.App.java
+.RouteConfiguration.java
 [source,java]
 ----
-
-@Bean
-public RouteLocator customRouteLocator(RouteLocatorBuilder builder) {
-    return builder.routes()
-            .route("resource", r -> r.path("/resource")
-                    .filters(f -> f.tokenRelay())
-                    .uri("http://localhost:9000"))
-            .build();
+import static org.springframework.cloud.gateway.server.mvc.filter.TokenRelayFilterFunctions.tokenRelay;
+import static org.springframework.cloud.gateway.server.mvc.handler.GatewayRouterFunctions.route;
+import static org.springframework.cloud.gateway.server.mvc.handler.HandlerFunctions.http;
+
+@Configuration
+class RouteConfiguration {
+
+    @Bean
+    public RouterFunction<ServerResponse> gatewayRouterFunctionsAddReqHeader() {
+		return route("resource")
+			.GET("/resource", http("http://localhost:9000"))
+				.filter(tokenRelay())
+				.build();
+    }
 }
 ----
 
@@ -70,34 +79,33 @@ or this
 spring:
   cloud:
     gateway:
-      routes:
-      - id: resource
-        uri: http://localhost:9000
-        predicates:
-        - Path=/resource
-        filters:
-        - TokenRelay=
+      mvc:
+        routes:
+        - id: resource
+          uri: http://localhost:9000
+          predicates:
+          - Path=/resource
+          filters:
+          - TokenRelay=
 ----
 
 and it will (in addition to logging the user in and grabbing a token)
 pass the authentication token downstream to the services (in this case
 `/resource`).
 
-To enable this for Spring Cloud Gateway add the following dependencies
+To enable this for Spring Cloud Gateway Server MVC add the following dependencies
 
 - `org.springframework.boot:spring-boot-starter-oauth2-client`
 
-How does it work?  The {github-code}/src/main/java/org/springframework/cloud/gateway/security/TokenRelayGatewayFilterFactory.java[filter]
-extracts an OAuth2 access token from the currently authenticated user for the provided `clientRegistrationId`.
-If no `clientRegistrationId` is provided, the currently authenticated user's own access token (obtained during login) is used.
-In either case, the extracted access token is placed in a request header for the downstream requests.
+How does it work?
+// The filter extracts an OAuth2 access token from the currently authenticated user for the provided `clientRegistrationId`.
+// If no `clientRegistrationId` is provided,
+The currently authenticated user's own access token (obtained during login) is used and the extracted access token is placed in a request header for the downstream requests.
 
-For a full working sample see https://github.com/spring-cloud-samples/sample-gateway-oauth2login[this project].
+//For a full working sample see https://github.com/spring-cloud-samples/sample-gateway-oauth2login[this project].
 
-NOTE: A `TokenRelayGatewayFilterFactory` bean will only be created if the proper `spring.security.oauth2.client.*` properties are set which will trigger creation of a `ReactiveClientRegistrationRepository` bean.
+NOTE: The Token Relay filter will only work if the proper `spring.security.oauth2.client.*` properties are set which will trigger creation of a `OAuth2AuthorizedClientManager` bean.
 
-NOTE: The default implementation of `ReactiveOAuth2AuthorizedClientService` used by `TokenRelayGatewayFilterFactory`
-uses an in-memory data store.  You will need to provide your own implementation `ReactiveOAuth2AuthorizedClientService`
+NOTE: The default implementation used by the Token Relay filter
+uses an in-memory data store.  You will need to provide your own implementation `OAuth2AuthorizedClientService`
 if you need a more robust solution.
-
-