Multiple WebFlux ResourceHandlerRegistrationCustomizer should be invoked

Before this commit, only a single ResourceHandlerRegistrationCustomizer
was invoked. This commit adds functionality to have more
than one ResourceHandlerRegistrationCustomizers

See gh-43494

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfiguration.java

@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.web.reactive;
 
 import java.time.Duration;
+import java.util.List;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -163,14 +164,14 @@ public class WebFluxAutoConfiguration {
 
 		private final ObjectProvider<CodecCustomizer> codecCustomizers;
 
-		private final ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;
+		private final ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizers;
 
 		private final ObjectProvider<ViewResolver> viewResolvers;
 
 		public WebFluxConfig(Environment environment, WebProperties webProperties, WebFluxProperties webFluxProperties,
 				ListableBeanFactory beanFactory, ObjectProvider<HandlerMethodArgumentResolver> resolvers,
 				ObjectProvider<CodecCustomizer> codecCustomizers,
-				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizer,
+				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizers,
 				ObjectProvider<ViewResolver> viewResolvers) {
 			this.environment = environment;
 			this.resourceProperties = webProperties.getResources();
@@ -178,7 +179,7 @@ public class WebFluxAutoConfiguration {
 			this.beanFactory = beanFactory;
 			this.argumentResolvers = resolvers;
 			this.codecCustomizers = codecCustomizers;
-			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizer.getIfAvailable();
+			this.resourceHandlerRegistrationCustomizers = resourceHandlerRegistrationCustomizers;
 			this.viewResolvers = viewResolvers;
 		}
 
@@ -210,19 +211,22 @@ public class WebFluxAutoConfiguration {
 				logger.debug("Default resource handling disabled");
 				return;
 			}
+			List<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizers = this.resourceHandlerRegistrationCustomizers
+				.orderedStream()
+				.toList();
 			String webjarsPathPattern = this.webFluxProperties.getWebjarsPathPattern();
 			if (!registry.hasMappingForPattern(webjarsPathPattern)) {
 				ResourceHandlerRegistration registration = registry.addResourceHandler(webjarsPathPattern)
 					.addResourceLocations("classpath:/META-INF/resources/webjars/");
 				configureResourceCaching(registration);
-				customizeResourceHandlerRegistration(registration);
+				resourceHandlerRegistrationCustomizers.forEach((customizer) -> customizer.customize(registration));
 			}
 			String staticPathPattern = this.webFluxProperties.getStaticPathPattern();
 			if (!registry.hasMappingForPattern(staticPathPattern)) {
 				ResourceHandlerRegistration registration = registry.addResourceHandler(staticPathPattern)
 					.addResourceLocations(this.resourceProperties.getStaticLocations());
 				configureResourceCaching(registration);
-				customizeResourceHandlerRegistration(registration);
+				resourceHandlerRegistrationCustomizers.forEach((customizer) -> customizer.customize(registration));
 			}
 		}
 
@@ -247,12 +251,6 @@ public class WebFluxAutoConfiguration {
 			ApplicationConversionService.addBeans(registry, this.beanFactory);
 		}
 
-		private void customizeResourceHandlerRegistration(ResourceHandlerRegistration registration) {
-			if (this.resourceHandlerRegistrationCustomizer != null) {
-				this.resourceHandlerRegistrationCustomizer.customize(registration);
-			}
-		}
-
 	}
 
 	/**

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/reactive/WebFluxAutoConfigurationTests.java

@@ -90,6 +90,7 @@ import org.springframework.web.reactive.HandlerMapping;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.config.BlockingExecutionConfigurer;
 import org.springframework.web.reactive.config.DelegatingWebFluxConfiguration;
+import org.springframework.web.reactive.config.ResourceHandlerRegistration;
 import org.springframework.web.reactive.config.WebFluxConfigurationSupport;
 import org.springframework.web.reactive.config.WebFluxConfigurer;
 import org.springframework.web.reactive.function.server.support.RouterFunctionMapping;
@@ -122,6 +123,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.BDDMockito.then;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.times;
 
 /**
  * Tests for {@link WebFluxAutoConfiguration}.
@@ -182,6 +184,18 @@ class WebFluxAutoConfigurationTests {
 		});
 	}
 
+	@Test
+	void shouldCustomizeResources() {
+		this.contextRunner.withUserConfiguration(ResourceHandlerRegistrationCustomizers.class).run((context) -> {
+			ResourceHandlerRegistrationCustomizer customizer1 = context
+				.getBean("firstResourceHandlerRegistrationCustomizer", ResourceHandlerRegistrationCustomizer.class);
+			ResourceHandlerRegistrationCustomizer customizer2 = context
+				.getBean("secondResourceHandlerRegistrationCustomizer", ResourceHandlerRegistrationCustomizer.class);
+			then(customizer1).should(times(2)).customize(any(ResourceHandlerRegistration.class));
+			then(customizer2).should(times(2)).customize(any(ResourceHandlerRegistration.class));
+		});
+	}
+
 	@Test
 	void shouldRegisterResourceHandlerMapping() {
 		this.contextRunner.run((context) -> {
@@ -843,6 +857,21 @@ class WebFluxAutoConfigurationTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class ResourceHandlerRegistrationCustomizers {
+
+		@Bean
+		ResourceHandlerRegistrationCustomizer firstResourceHandlerRegistrationCustomizer() {
+			return mock(ResourceHandlerRegistrationCustomizer.class);
+		}
+
+		@Bean
+		ResourceHandlerRegistrationCustomizer secondResourceHandlerRegistrationCustomizer() {
+			return mock(ResourceHandlerRegistrationCustomizer.class);
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	static class ViewResolvers {