Work around unwanted static resource warnings from WebFlux and MVC

See gh-28223

Author: wilkinsona

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -17,6 +17,8 @@
 package org.springframework.boot.autoconfigure.web.reactive;
 
 import java.time.Duration;
+import java.util.ArrayList;
+import java.util.List;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -49,6 +51,7 @@
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.core.Ordered;
+import org.springframework.core.io.ResourceLoader;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.format.support.FormattingConversionService;
 import org.springframework.http.codec.ServerCodecConfigurer;
@@ -151,12 +154,14 @@ public static class WebFluxConfig implements WebFluxConfigurer {
 
 		private final ObjectProvider<ViewResolver> viewResolvers;
 
+		private final ResourceLoader resourceLoader;
+
 		public WebFluxConfig(org.springframework.boot.autoconfigure.web.ResourceProperties resourceProperties,
 				WebProperties webProperties, WebFluxProperties webFluxProperties, ListableBeanFactory beanFactory,
 				ObjectProvider<HandlerMethodArgumentResolver> resolvers,
 				ObjectProvider<CodecCustomizer> codecCustomizers,
 				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizer,
-				ObjectProvider<ViewResolver> viewResolvers) {
+				ObjectProvider<ViewResolver> viewResolvers, ResourceLoader resourceLoader) {
 			this.resourceProperties = resourceProperties.hasBeenCustomized() ? resourceProperties
 					: webProperties.getResources();
 			this.webFluxProperties = webFluxProperties;
@@ -165,6 +170,7 @@ public WebFluxConfig(org.springframework.boot.autoconfigure.web.ResourceProperti
 			this.codecCustomizers = codecCustomizers;
 			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizer.getIfAvailable();
 			this.viewResolvers = viewResolvers;
+			this.resourceLoader = resourceLoader;
 		}
 
 		@Override
@@ -184,17 +190,28 @@ public void addResourceHandlers(ResourceHandlerRegistry registry) {
 				return;
 			}
 			if (!registry.hasMappingForPattern("/webjars/**")) {
-				ResourceHandlerRegistration registration = registry.addResourceHandler("/webjars/**")
-						.addResourceLocations("classpath:/META-INF/resources/webjars/");
-				configureResourceCaching(registration);
-				customizeResourceHandlerRegistration(registration);
+				String webjarsLocation = "classpath:/META-INF/resources/webjars/";
+				if (this.resourceLoader.getResource(webjarsLocation).exists()) {
+					ResourceHandlerRegistration registration = registry.addResourceHandler("/webjars/**")
+							.addResourceLocations(webjarsLocation);
+					configureResourceCaching(registration);
+					customizeResourceHandlerRegistration(registration);
+				}
 			}
 			String staticPathPattern = this.webFluxProperties.getStaticPathPattern();
 			if (!registry.hasMappingForPattern(staticPathPattern)) {
-				ResourceHandlerRegistration registration = registry.addResourceHandler(staticPathPattern)
-						.addResourceLocations(this.resourceProperties.getStaticLocations());
-				configureResourceCaching(registration);
-				customizeResourceHandlerRegistration(registration);
+				List<String> foundLocations = new ArrayList<>();
+				for (String staticLocation : this.resourceProperties.getStaticLocations()) {
+					if (this.resourceLoader.getResource(staticLocation).exists()) {
+						foundLocations.add(staticLocation);
+					}
+				}
+				if (!foundLocations.isEmpty()) {
+					ResourceHandlerRegistration registration = registry.addResourceHandler(staticPathPattern)
+							.addResourceLocations(foundLocations.toArray(new String[0]));
+					configureResourceCaching(registration);
+					customizeResourceHandlerRegistration(registration);
+				}
 			}
 		}
 

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration.java

@@ -201,6 +201,8 @@ public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer,
 
 		private final ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;
 
+		private final ResourceLoader resourceLoader;
+
 		private ServletContext servletContext;
 
 		public WebMvcAutoConfigurationAdapter(
@@ -209,7 +211,7 @@ public WebMvcAutoConfigurationAdapter(
 				ObjectProvider<HttpMessageConverters> messageConvertersProvider,
 				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
 				ObjectProvider<DispatcherServletPath> dispatcherServletPath,
-				ObjectProvider<ServletRegistrationBean<?>> servletRegistrations) {
+				ObjectProvider<ServletRegistrationBean<?>> servletRegistrations, ResourceLoader resourceLoader) {
 			this.resourceProperties = resourceProperties.hasBeenCustomized() ? resourceProperties
 					: webProperties.getResources();
 			this.mvcProperties = mvcProperties;
@@ -218,6 +220,7 @@ public WebMvcAutoConfigurationAdapter(
 			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
 			this.dispatcherServletPath = dispatcherServletPath;
 			this.servletRegistrations = servletRegistrations;
+			this.resourceLoader = resourceLoader;
 			this.mvcProperties.checkConfiguration();
 		}
 
@@ -334,7 +337,11 @@ public void addResourceHandlers(ResourceHandlerRegistry registry) {
 				logger.debug("Default resource handling disabled");
 				return;
 			}
-			addResourceHandler(registry, "/webjars/**", "classpath:/META-INF/resources/webjars/");
+			Resource webjarsLocationResource = this.resourceLoader
+					.getResource("classpath:/META-INF/resources/webjars/");
+			if (webjarsLocationResource.exists()) {
+				addResourceHandler(registry, "/webjars/**", webjarsLocationResource);
+			}
 			addResourceHandler(registry, this.mvcProperties.getStaticPathPattern(), (registration) -> {
 				registration.addResourceLocations(this.resourceProperties.getStaticLocations());
 				if (this.servletContext != null) {
@@ -344,7 +351,7 @@ public void addResourceHandlers(ResourceHandlerRegistry registry) {
 			});
 		}
 
-		private void addResourceHandler(ResourceHandlerRegistry registry, String pattern, String... locations) {
+		private void addResourceHandler(ResourceHandlerRegistry registry, String pattern, Resource... locations) {
 			addResourceHandler(registry, pattern, (registration) -> registration.addResourceLocations(locations));
 		}
 

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

@@ -150,9 +150,10 @@ void shouldRegisterResourceHandlerMapping() {
 			SimpleUrlHandlerMapping hm = context.getBean("resourceHandlerMapping", SimpleUrlHandlerMapping.class);
 			assertThat(hm.getUrlMap().get("/**")).isInstanceOf(ResourceWebHandler.class);
 			ResourceWebHandler staticHandler = (ResourceWebHandler) hm.getUrlMap().get("/**");
-			assertThat(staticHandler).extracting("locationValues").asList().hasSize(4);
-			assertThat(staticHandler.getLocations()).hasSize(1);
-			assertThat(staticHandler.getLocations().get(0)).hasToString("class path resource [public/]");
+			assertThat(staticHandler).extracting("locationValues").asList().hasSize(2);
+			assertThat(staticHandler.getLocations()).hasSize(2);
+			assertThat(staticHandler.getLocations().get(0)).hasToString("class path resource [META-INF/resources/]");
+			assertThat(staticHandler.getLocations().get(1)).hasToString("class path resource [public/]");
 			assertThat(hm.getUrlMap().get("/webjars/**")).isInstanceOf(ResourceWebHandler.class);
 			ResourceWebHandler webjarsHandler = (ResourceWebHandler) hm.getUrlMap().get("/webjars/**");
 			assertThat(webjarsHandler).extracting("locationValues").asList()
@@ -166,7 +167,7 @@ void shouldMapResourcesToCustomPath() {
 			SimpleUrlHandlerMapping hm = context.getBean("resourceHandlerMapping", SimpleUrlHandlerMapping.class);
 			assertThat(hm.getUrlMap().get("/static/**")).isInstanceOf(ResourceWebHandler.class);
 			ResourceWebHandler staticHandler = (ResourceWebHandler) hm.getUrlMap().get("/static/**");
-			assertThat(staticHandler).extracting("locationValues").asList().hasSize(4);
+			assertThat(staticHandler).extracting("locationValues").asList().hasSize(2);
 		});
 	}