Register default resource path using a Resource

Update `WebMvcAutoConfiguration` so that the default "/" resource path
is registered directly as a `ServletContextResource`.

Closes gh-24745

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfiguration.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.
@@ -17,13 +17,14 @@
 package org.springframework.boot.autoconfigure.web.servlet;
 
 import java.time.Duration;
-import java.util.Arrays;
+import java.util.HashSet;
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Map;
-import java.util.Optional;
+import java.util.Set;
 
 import javax.servlet.Servlet;
+import javax.servlet.ServletContext;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -70,10 +71,10 @@ import org.springframework.core.io.ResourceLoader;
 import org.springframework.core.task.AsyncTaskExecutor;
 import org.springframework.format.FormatterRegistry;
 import org.springframework.format.support.FormattingConversionService;
-import org.springframework.http.CacheControl;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.PathMatcher;
 import org.springframework.validation.DefaultMessageCodesResolver;
 import org.springframework.validation.MessageCodesResolver;
 import org.springframework.validation.Validator;
@@ -85,11 +86,13 @@ import org.springframework.web.bind.support.ConfigurableWebBindingInitializer;
 import org.springframework.web.context.request.NativeWebRequest;
 import org.springframework.web.context.request.RequestAttributes;
 import org.springframework.web.context.request.RequestContextListener;
+import org.springframework.web.context.support.ServletContextResource;
 import org.springframework.web.filter.FormContentFilter;
 import org.springframework.web.filter.HiddenHttpMethodFilter;
 import org.springframework.web.filter.RequestContextFilter;
 import org.springframework.web.servlet.DispatcherServlet;
 import org.springframework.web.servlet.HandlerExceptionResolver;
+import org.springframework.web.servlet.HandlerMapping;
 import org.springframework.web.servlet.LocaleResolver;
 import org.springframework.web.servlet.View;
 import org.springframework.web.servlet.ViewResolver;
@@ -104,6 +107,7 @@ import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 import org.springframework.web.servlet.handler.AbstractHandlerExceptionResolver;
+import org.springframework.web.servlet.handler.SimpleUrlHandlerMapping;
 import org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver;
 import org.springframework.web.servlet.i18n.FixedLocaleResolver;
 import org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver;
@@ -111,12 +115,14 @@ import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandl
 import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
 import org.springframework.web.servlet.resource.AppCacheManifestTransformer;
 import org.springframework.web.servlet.resource.EncodedResourceResolver;
+import org.springframework.web.servlet.resource.ResourceHttpRequestHandler;
 import org.springframework.web.servlet.resource.ResourceResolver;
 import org.springframework.web.servlet.resource.ResourceUrlProvider;
 import org.springframework.web.servlet.resource.VersionResourceResolver;
 import org.springframework.web.servlet.view.BeanNameViewResolver;
 import org.springframework.web.servlet.view.ContentNegotiatingViewResolver;
 import org.springframework.web.servlet.view.InternalResourceViewResolver;
+import org.springframework.web.util.UrlPathHelper;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for {@link EnableWebMvc Web MVC}.
@@ -151,7 +157,7 @@ public class WebMvcAutoConfiguration {
 	 */
 	public static final String DEFAULT_SUFFIX = "";
 
-	private static final String[] SERVLET_LOCATIONS = { "/" };
+	private static final String SERVLET_LOCATION = "/";
 
 	@Bean
 	@ConditionalOnMissingBean(HiddenHttpMethodFilter.class)
@@ -167,13 +173,6 @@ public class WebMvcAutoConfiguration {
 		return new OrderedFormContentFilter();
 	}
 
-	static String[] getResourceLocations(String[] staticLocations) {
-		String[] locations = new String[staticLocations.length + SERVLET_LOCATIONS.length];
-		System.arraycopy(staticLocations, 0, locations, 0, staticLocations.length);
-		System.arraycopy(SERVLET_LOCATIONS, 0, locations, staticLocations.length, SERVLET_LOCATIONS.length);
-		return locations;
-	}
-
 	// Defined as a nested config to ensure WebMvcConfigurer is not read when not
 	// on the classpath
 	@Configuration(proxyBeanMethods = false)
@@ -182,26 +181,17 @@ public class WebMvcAutoConfiguration {
 	@Order(0)
 	public static class WebMvcAutoConfigurationAdapter implements WebMvcConfigurer {
 
-		private static final Log logger = LogFactory.getLog(WebMvcConfigurer.class);
-
-		private final ResourceProperties resourceProperties;
-
 		private final WebMvcProperties mvcProperties;
 
 		private final ListableBeanFactory beanFactory;
 
 		private final ObjectProvider<HttpMessageConverters> messageConvertersProvider;
 
-		final ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;
-
-		public WebMvcAutoConfigurationAdapter(ResourceProperties resourceProperties, WebMvcProperties mvcProperties,
-				ListableBeanFactory beanFactory, ObjectProvider<HttpMessageConverters> messageConvertersProvider,
-				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider) {
-			this.resourceProperties = resourceProperties;
+		public WebMvcAutoConfigurationAdapter(WebMvcProperties mvcProperties, ListableBeanFactory beanFactory,
+				ObjectProvider<HttpMessageConverters> messageConvertersProvider) {
 			this.mvcProperties = mvcProperties;
 			this.beanFactory = beanFactory;
 			this.messageConvertersProvider = messageConvertersProvider;
-			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
 		}
 
 		@Override
@@ -303,37 +293,6 @@ public class WebMvcAutoConfiguration {
 			ApplicationConversionService.addBeans(registry, this.beanFactory);
 		}
 
-		@Override
-		public void addResourceHandlers(ResourceHandlerRegistry registry) {
-			if (!this.resourceProperties.isAddMappings()) {
-				logger.debug("Default resource handling disabled");
-				return;
-			}
-			Duration cachePeriod = this.resourceProperties.getCache().getPeriod();
-			CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();
-			if (!registry.hasMappingForPattern("/webjars/**")) {
-				customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**")
-						.addResourceLocations("classpath:/META-INF/resources/webjars/")
-						.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
-			}
-			String staticPathPattern = this.mvcProperties.getStaticPathPattern();
-			if (!registry.hasMappingForPattern(staticPathPattern)) {
-				customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern)
-						.addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations()))
-						.setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));
-			}
-		}
-
-		private Integer getSeconds(Duration cachePeriod) {
-			return (cachePeriod != null) ? (int) cachePeriod.getSeconds() : null;
-		}
-
-		private void customizeResourceHandlerRegistration(ResourceHandlerRegistration registration) {
-			if (this.resourceHandlerRegistrationCustomizer != null) {
-				this.resourceHandlerRegistrationCustomizer.customize(registration);
-			}
-		}
-
 		@Bean
 		@ConditionalOnMissingBean({ RequestContextListener.class, RequestContextFilter.class })
 		@ConditionalOnMissingFilterBean(RequestContextFilter.class)
@@ -349,22 +308,31 @@ public class WebMvcAutoConfiguration {
 	@Configuration(proxyBeanMethods = false)
 	public static class EnableWebMvcConfiguration extends DelegatingWebMvcConfiguration implements ResourceLoaderAware {
 
+		private static final Log logger = LogFactory.getLog(WebMvcConfigurer.class);
+
 		private final ResourceProperties resourceProperties;
 
 		private final WebMvcProperties mvcProperties;
 
-		private final ListableBeanFactory beanFactory;
-
 		private final WebMvcRegistrations mvcRegistrations;
 
+		private final ResourceHandlerRegistrationCustomizer resourceHandlerRegistrationCustomizer;
+
 		private ResourceLoader resourceLoader;
 
+		private final ListableBeanFactory beanFactory;
+
+		private final Set<String> autoConfiguredResourceHandlers = new HashSet<>();
+
 		public EnableWebMvcConfiguration(ResourceProperties resourceProperties,
 				ObjectProvider<WebMvcProperties> mvcPropertiesProvider,
-				ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider, ListableBeanFactory beanFactory) {
+				ObjectProvider<WebMvcRegistrations> mvcRegistrationsProvider,
+				ObjectProvider<ResourceHandlerRegistrationCustomizer> resourceHandlerRegistrationCustomizerProvider,
+				ListableBeanFactory beanFactory) {
 			this.resourceProperties = resourceProperties;
 			this.mvcProperties = mvcPropertiesProvider.getIfAvailable();
 			this.mvcRegistrations = mvcRegistrationsProvider.getIfUnique();
+			this.resourceHandlerRegistrationCustomizer = resourceHandlerRegistrationCustomizerProvider.getIfAvailable();
 			this.beanFactory = beanFactory;
 		}
 
@@ -401,6 +369,72 @@ public class WebMvcAutoConfiguration {
 					resourceUrlProvider);
 		}
 
+		@Bean
+		@Override
+		public HandlerMapping resourceHandlerMapping(UrlPathHelper urlPathHelper, PathMatcher pathMatcher,
+				ContentNegotiationManager contentNegotiationManager, FormattingConversionService conversionService,
+				ResourceUrlProvider resourceUrlProvider) {
+			HandlerMapping mapping = super.resourceHandlerMapping(urlPathHelper, pathMatcher, contentNegotiationManager,
+					conversionService, resourceUrlProvider);
+			if (mapping instanceof SimpleUrlHandlerMapping) {
+				addServletContextResourceHandlerMapping((SimpleUrlHandlerMapping) mapping);
+			}
+			return mapping;
+		}
+
+		private void addServletContextResourceHandlerMapping(SimpleUrlHandlerMapping mapping) {
+			Map<String, ?> urlMap = mapping.getUrlMap();
+			String pattern = this.mvcProperties.getStaticPathPattern();
+			Object handler = urlMap.get(pattern);
+			if (handler instanceof ResourceHttpRequestHandler
+					&& this.autoConfiguredResourceHandlers.contains(pattern)) {
+				addServletContextResourceHandlerMapping((ResourceHttpRequestHandler) handler);
+			}
+		}
+
+		private void addServletContextResourceHandlerMapping(ResourceHttpRequestHandler handler) {
+			ServletContext servletContext = getServletContext();
+			if (servletContext != null) {
+				List<Resource> locations = handler.getLocations();
+				locations.add(new ServletContextResource(servletContext, SERVLET_LOCATION));
+			}
+		}
+
+		@Override
+		protected void addResourceHandlers(ResourceHandlerRegistry registry) {
+			super.addResourceHandlers(registry);
+			if (!this.resourceProperties.isAddMappings()) {
+				logger.debug("Default resource handling disabled");
+				return;
+			}
+			addResourceHandler(registry, "/webjars/**", "classpath:/META-INF/resources/webjars/");
+			addResourceHandler(registry, this.mvcProperties.getStaticPathPattern(),
+					this.resourceProperties.getStaticLocations());
+
+		}
+
+		private void addResourceHandler(ResourceHandlerRegistry registry, String pattern, String... locations) {
+			if (registry.hasMappingForPattern(pattern)) {
+				return;
+			}
+			ResourceHandlerRegistration registration = registry.addResourceHandler(pattern);
+			registration.addResourceLocations(locations);
+			registration.setCachePeriod(getSeconds(this.resourceProperties.getCache().getPeriod()));
+			registration.setCacheControl(this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl());
+			customizeResourceHandlerRegistration(registration);
+			this.autoConfiguredResourceHandlers.add(pattern);
+		}
+
+		private Integer getSeconds(Duration cachePeriod) {
+			return (cachePeriod != null) ? (int) cachePeriod.getSeconds() : null;
+		}
+
+		private void customizeResourceHandlerRegistration(ResourceHandlerRegistration registration) {
+			if (this.resourceHandlerRegistrationCustomizer != null) {
+				this.resourceHandlerRegistrationCustomizer.customize(registration);
+			}
+		}
+
 		@Bean
 		public WelcomePageHandlerMapping welcomePageHandlerMapping(ApplicationContext applicationContext,
 				FormattingConversionService mvcConversionService, ResourceUrlProvider mvcResourceUrlProvider) {
@@ -412,22 +446,34 @@ public class WebMvcAutoConfiguration {
 			return welcomePageHandlerMapping;
 		}
 
-		private Optional<Resource> getWelcomePage() {
-			String[] locations = getResourceLocations(this.resourceProperties.getStaticLocations());
-			return Arrays.stream(locations).map(this::getIndexHtml).filter(this::isReadable).findFirst();
+		private Resource getWelcomePage() {
+			for (String location : this.resourceProperties.getStaticLocations()) {
+				Resource indexHtml = getIndexHtml(location);
+				if (indexHtml != null) {
+					return indexHtml;
+				}
+			}
+			ServletContext servletContext = getServletContext();
+			if (servletContext != null) {
+				return getIndexHtml(new ServletContextResource(servletContext, SERVLET_LOCATION));
+			}
+			return null;
 		}
 
 		private Resource getIndexHtml(String location) {
-			return this.resourceLoader.getResource(location + "index.html");
+			return getIndexHtml(this.resourceLoader.getResource(location));
 		}
 
-		private boolean isReadable(Resource resource) {
+		private Resource getIndexHtml(Resource location) {
 			try {
-				return resource.exists() && (resource.getURL() != null);
+				Resource resource = location.createRelative("index.html");
+				if (resource.exists() && (resource.getURL() != null)) {
+					return resource;
+				}
 			}
 			catch (Exception ex) {
-				return false;
 			}
+			return null;
 		}
 
 		@Bean

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 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.
@@ -18,7 +18,6 @@ package org.springframework.boot.autoconfigure.web.servlet;
 
 import java.util.Collections;
 import java.util.List;
-import java.util.Optional;
 
 import javax.servlet.http.HttpServletRequest;
 
@@ -49,9 +48,9 @@ final class WelcomePageHandlerMapping extends AbstractUrlHandlerMapping {
 	private static final List<MediaType> MEDIA_TYPES_ALL = Collections.singletonList(MediaType.ALL);
 
 	WelcomePageHandlerMapping(TemplateAvailabilityProviders templateAvailabilityProviders,
-			ApplicationContext applicationContext, Optional<Resource> welcomePage, String staticPathPattern) {
-		if (welcomePage.isPresent() && "/**".equals(staticPathPattern)) {
-			logger.info("Adding welcome page: " + welcomePage.get());
+			ApplicationContext applicationContext, Resource welcomePage, String staticPathPattern) {
+		if (welcomePage != null && "/**".equals(staticPathPattern)) {
+			logger.info("Adding welcome page: " + welcomePage);
 			setRootViewName("forward:index.html");
 		}
 		else if (welcomeTemplateExists(templateAvailabilityProviders, applicationContext)) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/WebMvcAutoConfigurationTests.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.
@@ -814,7 +814,7 @@ class WebMvcAutoConfigurationTests {
 	protected Map<String, List<Resource>> getResourceMappingLocations(ApplicationContext context) {
 		Object bean = context.getBean("resourceHandlerMapping");
 		if (bean instanceof HandlerMapping) {
-			return getMappingLocations(context.getBean("resourceHandlerMapping", HandlerMapping.class));
+			return getMappingLocations((HandlerMapping) bean);
 		}
 		assertThat(bean.toString()).isEqualTo("null");
 		return Collections.emptyMap();

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/servlet/WelcomePageHandlerMappingTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2019 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.
@@ -18,7 +18,6 @@ package org.springframework.boot.autoconfigure.web.servlet;
 
 import java.util.Collections;
 import java.util.Map;
-import java.util.Optional;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
@@ -162,8 +161,7 @@ class WelcomePageHandlerMappingTests {
 			return new WelcomePageHandlerMapping(
 					templateAvailabilityProviders
 							.getIfAvailable(() -> new TemplateAvailabilityProviders(applicationContext)),
-					applicationContext, Optional.ofNullable(staticIndexPage.getIfAvailable()), staticPathPattern);
-
+					applicationContext, staticIndexPage.getIfAvailable(), staticPathPattern);
 		}
 
 	}