docs: add application-scoped access tokens example for reactive OAuth2 client

Signed-off-by: C0ng_yun <s25069@gsm.hs.kr>

docs/modules/ROOT/pages/reactive/oauth2/client/authorization-grants.adoc

@@ -340,7 +340,7 @@ class OAuth2ClientSecurityConfig {
 Please refer to the https://tools.ietf.org/html/rfc6749#section-4.1.3[Access Token Request/Response] protocol flow for the Authorization Code grant.
 ====
 
-The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Authorization Code grant is `WebClientReactiveAuthorizationCodeTokenResponseClient`, which uses a `WebClient` for exchanging an authorization code for an access token at the Authorization Server’s Token Endpoint.
+The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Authorization Code grant is `WebClientReactiveAuthorizationCodeTokenResponseClient`, which uses a `WebClient` for exchanging an authorization code for an access token at the Authorization Server's Token Endpoint.
 
 :section-id: authorization-code
 :grant-type: Authorization Code
@@ -432,7 +432,7 @@ Please refer to the OAuth 2.0 Authorization Framework for further details on the
 Please refer to the https://tools.ietf.org/html/rfc6749#section-6[Access Token Request/Response] protocol flow for the Refresh Token grant.
 ====
 
-The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Refresh Token grant is `WebClientReactiveRefreshTokenTokenResponseClient`, which uses a `WebClient` when refreshing an access token at the Authorization Server’s Token Endpoint.
+The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Refresh Token grant is `WebClientReactiveRefreshTokenTokenResponseClient`, which uses a `WebClient` when refreshing an access token at the Authorization Server's Token Endpoint.
 
 :section-id: refresh-token
 :grant-type: Refresh Token
@@ -512,7 +512,7 @@ Please refer to the OAuth 2.0 Authorization Framework for further details on the
 Please refer to the https://tools.ietf.org/html/rfc6749#section-4.4.2[Access Token Request/Response] protocol flow for the Client Credentials grant.
 ====
 
-The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Client Credentials grant is `WebClientReactiveClientCredentialsTokenResponseClient`, which uses a `WebClient` when requesting an access token at the Authorization Server’s Token Endpoint.
+The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Client Credentials grant is `WebClientReactiveClientCredentialsTokenResponseClient`, which uses a `WebClient` when requesting an access token at the Authorization Server's Token Endpoint.
 
 :section-id: client-credentials
 :grant-type: Client Credentials
@@ -698,6 +698,31 @@ class OAuth2ClientController {
 If not provided, it will be obtained from the https://projectreactor.io/docs/core/release/reference/#context[Reactor's Context] via the key `ServerWebExchange.class`.
 ====
 
+[[oauth2-client-client-credentials-application-scoped]]
+=== Use the Client Credentials Grant for Application-Scoped Access Tokens
+
+When making requests that are not associated with a specific user (e.g. background jobs, batch processes, or scheduled tasks), use `AuthorizedClientServiceReactiveOAuth2AuthorizedClientManager` instead of `DefaultReactiveOAuth2AuthorizedClientManager`.
+Unlike `DefaultReactiveOAuth2AuthorizedClientManager`, `AuthorizedClientServiceReactiveOAuth2AuthorizedClientManager` operates outside of a `ServerWebExchange` context, making it suitable for application-scoped access tokens.
+
+The following example shows how to configure a `WebClient` for application-scoped access tokens using the Client Credentials grant:
+
+.WebClient with Application-Scoped Access Tokens
+[tabs]
+======
+Java::
++
+[source,java,role="primary",indent=0]
+----
+include::{tests-dir}/reactive/oauth2/webclient/ApplicationScopedAccessTokenConfiguration.java[tag=webclient-client-credentials]
+----
+======
+
+[NOTE]
+====
+`AuthorizedClientServiceReactiveOAuth2AuthorizedClientManager` uses a `ReactiveOAuth2AuthorizedClientService` to persist authorized clients, rather than a `ServerOAuth2AuthorizedClientRepository`.
+This makes it suitable for use cases where there is no active `ServerWebExchange`, such as background tasks or scheduled jobs.
+====
+
 [[oauth2-client-jwt-bearer]]
 == JWT Bearer
 
@@ -714,7 +739,7 @@ Please refer to JSON Web Token (JWT) Profile for OAuth 2.0 Client Authentication
 Please refer to the https://datatracker.ietf.org/doc/html/rfc7523#section-2.1[Access Token Request/Response] protocol flow for the JWT Bearer grant.
 ====
 
-The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the JWT Bearer grant is `WebClientReactiveJwtBearerTokenResponseClient`, which uses a `WebClient` when requesting an access token at the Authorization Server’s Token Endpoint.
+The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the JWT Bearer grant is `WebClientReactiveJwtBearerTokenResponseClient`, which uses a `WebClient` when requesting an access token at the Authorization Server's Token Endpoint.
 
 :section-id: jwt-bearer
 :grant-type: JWT Bearer
@@ -922,7 +947,7 @@ Please refer to OAuth 2.0 Token Exchange for further details on the https://data
 Please refer to the https://datatracker.ietf.org/doc/html/rfc8693#section-2[Token Exchange Request and Response] protocol flow for the Token Exchange grant.
 ====
 
-The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Token Exchange grant is `WebClientReactiveTokenExchangeTokenResponseClient`, which uses a `WebClient` when requesting an access token at the Authorization Server’s Token Endpoint.
+The default implementation of `ReactiveOAuth2AccessTokenResponseClient` for the Token Exchange grant is `WebClientReactiveTokenExchangeTokenResponseClient`, which uses a `WebClient` when requesting an access token at the Authorization Server's Token Endpoint.
 
 :section-id: token-exchange
 :grant-type: Token Exchange

docs/src/test/java/org/springframework/security/docs/reactive/oauth2/webclient/ApplicationScopedAccessTokenConfiguration.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2002-2024 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.docs.reactive.oauth2.webclient;
+
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.oauth2.client.AuthorizedClientServiceReactiveOAuth2AuthorizedClientManager;
+import org.springframework.security.oauth2.client.ReactiveOAuth2AuthorizedClientManager;
+import org.springframework.security.oauth2.client.ReactiveOAuth2AuthorizedClientProviderBuilder;
+import org.springframework.security.oauth2.client.ReactiveOAuth2AuthorizedClientService;
+import org.springframework.security.oauth2.client.registration.ReactiveClientRegistrationRepository;
+import org.springframework.security.oauth2.client.web.reactive.function.client.ServerOAuth2AuthorizedClientExchangeFilterFunction;
+import org.springframework.web.reactive.function.client.WebClient;
+
+@Configuration
+public class ApplicationScopedAccessTokenConfiguration {
+
+	// tag::webclient-client-credentials[]
+	@Bean
+	ReactiveOAuth2AuthorizedClientManager authorizedClientManager(
+			ReactiveClientRegistrationRepository clientRegistrationRepository,
+			ReactiveOAuth2AuthorizedClientService authorizedClientService) {
+
+		var authorizedClientProvider = ReactiveOAuth2AuthorizedClientProviderBuilder.builder()
+				.clientCredentials()
+				.build();
+
+		var authorizedClientManager = new AuthorizedClientServiceReactiveOAuth2AuthorizedClientManager(
+				clientRegistrationRepository, authorizedClientService);
+		authorizedClientManager.setAuthorizedClientProvider(authorizedClientProvider);
+
+		return authorizedClientManager;
+	}
+
+	@Bean
+	WebClient webClient(ReactiveOAuth2AuthorizedClientManager authorizedClientManager) {
+		var oauth2Client = new ServerOAuth2AuthorizedClientExchangeFilterFunction(authorizedClientManager);
+		oauth2Client.setDefaultClientRegistrationId("my-client");
+
+		return WebClient.builder()
+				.filter(oauth2Client)
+				.build();
+	}
+	// end::webclient-client-credentials[]
+
+}

docs/src/test/java/org/springframework/security/docs/reactive/oauth2/webclient/ApplicationScopedAccessTokenTests.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2004-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.docs.reactive.oauth2.webclient;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mockito;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.security.config.test.SpringTestContext;
+import org.springframework.security.config.test.SpringTestContextExtension;
+import org.springframework.security.oauth2.client.ReactiveOAuth2AuthorizedClientService;
+import org.springframework.security.oauth2.client.registration.ReactiveClientRegistrationRepository;
+import org.springframework.web.reactive.function.client.WebClient;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests {@link ApplicationScopedAccessTokenConfiguration}.
+ */
+@ExtendWith(SpringTestContextExtension.class)
+public class ApplicationScopedAccessTokenTests {
+
+	public final SpringTestContext spring = new SpringTestContext(this);
+
+	@Autowired
+	WebClient webClient;
+
+	@Test
+	void webClientWhenClientCredentialsThenConfigured() {
+		this.spring.register(TestConfig.class, ApplicationScopedAccessTokenConfiguration.class).autowire();
+		assertThat(this.webClient).isNotNull();
+	}
+
+	@Configuration
+	static class TestConfig {
+
+		@Bean
+		ReactiveClientRegistrationRepository clientRegistrationRepository() {
+			return Mockito.mock(ReactiveClientRegistrationRepository.class);
+		}
+
+		@Bean
+		ReactiveOAuth2AuthorizedClientService authorizedClientService() {
+			return Mockito.mock(ReactiveOAuth2AuthorizedClientService.class);
+		}
+
+	}
+
+}