Allow configuration of oauth2 client through nested builder

Issue: spring-projectsgh-5557

Author: eleftherias

config/src/main/java/org/springframework/security/config/annotation/web/builders/HttpSecurity.java

@@ -2059,6 +2059,41 @@ public OAuth2ClientConfigurer<HttpSecurity> oauth2Client() throws Exception {
 		return configurer;
 	}
 
+	/**
+	 * Configures OAuth 2.0 Client support.
+	 *
+	 * <h2>Example Configuration</h2>
+	 *
+	 * The following example demonstrates how to enable OAuth 2.0 Client support for all endpoints.
+	 *
+	 * <pre>
+	 * &#064;Configuration
+	 * &#064;EnableWebSecurity
+	 * public class OAuth2ClientSecurityConfig extends WebSecurityConfigurerAdapter {
+	 * 	&#064;Override
+	 * 	protected void configure(HttpSecurity http) throws Exception {
+	 * 		http
+	 * 			.authorizeRequests(authorizeRequests ->
+	 * 				authorizeRequests
+	 * 					.anyRequest().authenticated()
+	 * 			)
+	 * 			.oauth2Client(withDefaults());
+	 *	}
+	 * }
+	 * </pre>
+	 *
+	 * @see <a target="_blank" href="https://tools.ietf.org/html/rfc6749#section-1.1">OAuth 2.0 Authorization Framework</a>
+	 *
+	 * @param oauth2ClientCustomizer the {@link Customizer} to provide more options for
+	 * the {@link OAuth2ClientConfigurer}
+	 * @return the {@link HttpSecurity} for further customizations
+	 * @throws Exception
+	 */
+	public HttpSecurity oauth2Client(Customizer<OAuth2ClientConfigurer<HttpSecurity>> oauth2ClientCustomizer) throws Exception {
+		oauth2ClientCustomizer.customize(getOrApply(new OAuth2ClientConfigurer<>()));
+		return HttpSecurity.this;
+	}
+
 	/**
 	 * Configures OAuth 2.0 Resource Server support.
 	 *

config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2ClientConfigurer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2019 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.
@@ -16,6 +16,7 @@
 package org.springframework.security.config.annotation.web.configurers.oauth2.client;
 
 import org.springframework.security.authentication.AuthenticationManager;
+import org.springframework.security.config.Customizer;
 import org.springframework.security.config.annotation.web.HttpSecurityBuilder;
 import org.springframework.security.config.annotation.web.configurers.AbstractHttpConfigurer;
 import org.springframework.security.oauth2.client.OAuth2AuthorizedClientService;
@@ -135,6 +136,20 @@ public AuthorizationCodeGrantConfigurer authorizationCodeGrant() {
 		return this.authorizationCodeGrantConfigurer;
 	}
 
+	/**
+	 * Configures the OAuth 2.0 Authorization Code Grant.
+	 *
+	 * @param authorizationCodeGrantCustomizer the {@link Customizer} to provide more options for
+	 * the {@link AuthorizationCodeGrantConfigurer}
+	 * @return the {@link OAuth2ClientConfigurer} for further customizations
+	 * @throws Exception
+	 */
+	public OAuth2ClientConfigurer<B> authorizationCodeGrant(Customizer<AuthorizationCodeGrantConfigurer> authorizationCodeGrantCustomizer)
+			throws Exception {
+		authorizationCodeGrantCustomizer.customize(this.authorizationCodeGrantConfigurer);
+		return this;
+	}
+
 	/**
 	 * Configuration options for the OAuth 2.0 Authorization Code Grant.
 	 */

config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2ClientConfigurerTests.java

@@ -65,6 +65,7 @@
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.*;
+import static org.springframework.security.config.Customizer.withDefaults;
 import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.authentication;
 import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.user;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
@@ -141,6 +142,19 @@ public void configureWhenAuthorizationCodeRequestThenRedirectForAuthorization()
 				"redirect_uri=http://localhost/client-1");
 	}
 
+	@Test
+	public void configureWhenOauth2ClientInLambdaThenRedirectForAuthorization() throws Exception {
+		this.spring.register(OAuth2ClientInLambdaConfig.class).autowire();
+
+		MvcResult mvcResult = this.mockMvc.perform(get("/oauth2/authorization/registration-1"))
+			.andExpect(status().is3xxRedirection())
+			.andReturn();
+		assertThat(mvcResult.getResponse().getRedirectedUrl()).matches("https://provider.com/oauth2/authorize\\?" +
+				"response_type=code&client_id=client-1&" +
+				"scope=user&state=.{15,}&" +
+				"redirect_uri=http://localhost/client-1");
+	}
+
 	@Test
 	public void configureWhenAuthorizationCodeResponseSuccessThenAuthorizedClientSaved() throws Exception {
 		this.spring.register(OAuth2ClientConfig.class).autowire();
@@ -248,4 +262,30 @@ public String resource1(@RegisteredOAuth2AuthorizedClient("registration-1") OAut
 			}
 		}
 	}
+
+	@EnableWebSecurity
+	@EnableWebMvc
+	static class OAuth2ClientInLambdaConfig extends WebSecurityConfigurerAdapter {
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+				.authorizeRequests(authorizeRequests ->
+					authorizeRequests
+						.anyRequest().authenticated()
+				)
+				.oauth2Client(withDefaults());
+			// @formatter:on
+		}
+
+		@Bean
+		public ClientRegistrationRepository clientRegistrationRepository() {
+			return clientRegistrationRepository;
+		}
+
+		@Bean
+		public OAuth2AuthorizedClientRepository authorizedClientRepository() {
+			return authorizedClientRepository;
+		}
+	}
 }