Add additional pre-validation check in ResourceServerProperties

With this change a user can have `@EnableOAuth2Client` without
`@EnableOAuth2Sso`.

Fixes gh-3568

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/ResourceServerProperties.java

@@ -165,12 +165,16 @@ public class ResourceServerProperties implements Validator, BeanFactoryAware {
 
 	@Override
 	public void validate(Object target, Errors errors) {
-		if (BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory,
+		if (countBeans(AuthorizationServerEndpointsConfiguration.class) > 0) {
-				AuthorizationServerEndpointsConfiguration.class).length > 0) {
 			// If we are an authorization server we don't need remote resource token
 			// services
 			return;
 		}
+		if (countBeans(ResourceServerTokenServicesConfiguration.class) == 0) {
+			// If we are not a resource server or an SSO client we don't need remote
+			// resource token services
+			return;
+		}
 		ResourceServerProperties resource = (ResourceServerProperties) target;
 		if (StringUtils.hasText(this.clientId)) {
 			if (!StringUtils.hasText(this.clientSecret)) {
@@ -197,6 +201,11 @@ public class ResourceServerProperties implements Validator, BeanFactoryAware {
 		}
 	}
 
+	private int countBeans(Class<?> type) {
+		return BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this.beanFactory,
+				type, true, false).length;
+	}
+
 	public class Jwt {
 
 		/**

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/security/oauth2/OAuth2AutoConfigurationTests.java

@@ -16,6 +16,9 @@
 
 package org.springframework.boot.autoconfigure.security.oauth2;
 
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
 import java.net.URI;
 import java.util.Arrays;
 import java.util.List;
@@ -60,9 +63,11 @@ import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
 import org.springframework.security.core.authority.AuthorityUtils;
 import org.springframework.security.crypto.codec.Base64;
+import org.springframework.security.oauth2.client.OAuth2ClientContext;
 import org.springframework.security.oauth2.config.annotation.configurers.ClientDetailsServiceConfigurer;
 import org.springframework.security.oauth2.config.annotation.web.configuration.AuthorizationServerConfigurerAdapter;
 import org.springframework.security.oauth2.config.annotation.web.configuration.EnableAuthorizationServer;
+import org.springframework.security.oauth2.config.annotation.web.configuration.EnableOAuth2Client;
 import org.springframework.security.oauth2.config.annotation.web.configuration.EnableResourceServer;
 import org.springframework.security.oauth2.config.annotation.web.configuration.ResourceServerConfigurerAdapter;
 import org.springframework.security.oauth2.config.annotation.web.configurers.AuthorizationServerEndpointsConfigurer;
@@ -89,9 +94,6 @@ import org.springframework.web.client.RestTemplate;
 
 import com.fasterxml.jackson.databind.JsonNode;
 
-import static org.hamcrest.CoreMatchers.equalTo;
-import static org.hamcrest.MatcherAssert.assertThat;
-
 /**
  * Verify Spring Security OAuth2 auto-configuration secures end points properly, accepts
  * environmental overrides, and also backs off in the presence of other
@@ -159,6 +161,18 @@ public class OAuth2AutoConfigurationTests {
 		assertThat(countBeans(AUTHORIZATION_SERVER_CONFIG), equalTo(1));
 	}
 
+	@Test
+	public void testClientIsNotResourceServer() {
+		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
+		this.context.register(ClientConfiguration.class,
+				MinimalSecureWebApplication.class);
+		this.context.refresh();
+		assertThat(countBeans(RESOURCE_SERVER_CONFIG), equalTo(0));
+		assertThat(countBeans(AUTHORIZATION_SERVER_CONFIG), equalTo(0));
+		// Scoped target and proxy:
+		assertThat(countBeans(OAuth2ClientContext.class), equalTo(2));
+	}
+
 	@Test
 	public void testDisablingAuthorizationServer() {
 		this.context = new AnnotationConfigEmbeddedWebApplicationContext();
@@ -372,6 +386,11 @@ public class OAuth2AutoConfigurationTests {
 
 	}
 
+	@Configuration
+	@EnableOAuth2Client
+	protected static class ClientConfiguration extends TestSecurityConfiguration {
+	}
+
 	@Configuration
 	@EnableAuthorizationServer
 	@EnableResourceServer