Polish oauth2ResourceServer() Error Messaging

Fixes: gh-6876

config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/server/resource/OAuth2ResourceServerConfigurerTests.java

@@ -65,6 +65,7 @@ import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.security.access.prepost.PreAuthorize;
 import org.springframework.security.authentication.AbstractAuthenticationToken;
 import org.springframework.security.authentication.AuthenticationManager;
+import org.springframework.security.authentication.AuthenticationManagerResolver;
 import org.springframework.security.authentication.AuthenticationProvider;
 import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
 import org.springframework.security.config.annotation.web.HttpSecurityBuilder;
@@ -1358,6 +1359,13 @@ public class OAuth2ResourceServerConfigurerTests {
 				.hasMessageContaining("Spring Security only supports JWTs or Opaque Tokens");
 	}
 
+	@Test
+	public void configureWhenUsingBothAuthenticationManagerResolverAndOpaqueThenWiringException() {
+		assertThatCode(() -> this.spring.register(AuthenticationManagerResolverPlusOtherConfig.class).autowire())
+				.isInstanceOf(BeanCreationException.class)
+				.hasMessageContaining("authenticationManagerResolver");
+	}
+
 	// -- support
 
 	@EnableWebSecurity
@@ -2064,6 +2072,21 @@ public class OAuth2ResourceServerConfigurerTests {
 		}
 	}
 
+	@EnableWebSecurity
+	static class AuthenticationManagerResolverPlusOtherConfig extends WebSecurityConfigurerAdapter {
+		@Override
+		protected void configure(HttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+				.authorizeRequests()
+					.anyRequest().authenticated()
+					.and()
+				.oauth2ResourceServer()
+					.authenticationManagerResolver(mock(AuthenticationManagerResolver.class))
+					.opaqueToken();
+		}
+	}
+
 	@Configuration
 	static class JwtDecoderConfig {
 		@Bean

config/src/test/java/org/springframework/security/config/web/server/OAuth2ResourceServerSpecTests.java

@@ -41,6 +41,7 @@ import org.junit.Test;
 import org.junit.runner.RunWith;
 import reactor.core.publisher.Mono;
 
+import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.NoSuchBeanDefinitionException;
 import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -457,6 +458,13 @@ public class OAuth2ResourceServerSpecTests {
 				.expectStatus().isOk();
 	}
 
+	@Test
+	public void configureWhenUsingBothAuthenticationManagerResolverAndOpaqueThenWiringException() {
+		assertThatCode(() -> this.spring.register(AuthenticationManagerResolverPlusOtherConfig.class).autowire())
+				.isInstanceOf(BeanCreationException.class)
+				.hasMessageContaining("authenticationManagerResolver");
+	}
+
 	@EnableWebFlux
 	@EnableWebFluxSecurity
 	static class PublicKeyConfig {
@@ -849,6 +857,24 @@ public class OAuth2ResourceServerSpecTests {
 		}
 	}
 
+	@EnableWebFlux
+	@EnableWebFluxSecurity
+	static class AuthenticationManagerResolverPlusOtherConfig {
+		@Bean
+		SecurityWebFilterChain springSecurity(ServerHttpSecurity http) {
+			// @formatter:off
+			http
+				.authorizeExchange()
+					.anyExchange().authenticated()
+					.and()
+				.oauth2ResourceServer()
+					.authenticationManagerResolver(mock(ReactiveAuthenticationManagerResolver.class))
+					.opaqueToken();
+
+			return http.build();
+		}
+	}
+
 	@RestController
 	static class RootController {
 		@GetMapping