Configure ResourceUrlProvider in WebFlux

Prior to this commit, no `ResourceUrlProvider` was configured
in WebFlux (no bean was contributed by the WebFlux infrastructure).
Also, several `ResourceTransformer` instances that extend the
`ResourceTransformerSupport` base class need a `ResourceUrlProvider`
to resolve absolute URLs when rewriting resource URLs. At this point,
no `ResourceUrlProvider` was configured and they could only resolve
relative URLs.

This commit contributes a new `ResourceUrlProvider` to the WebFlux
configuration; this bean can be reused by the WebFlux infrastructure and
application code.

This also automatically configure this shared `ResourceUrlProvider`
instance on the resource chain where needed.

Issue: SPR-17433

spring-webflux/src/main/java/org/springframework/web/reactive/config/ResourceHandlerRegistry.java

@@ -28,6 +28,8 @@ import org.springframework.core.io.ResourceLoader;
 import org.springframework.lang.Nullable;
 import org.springframework.web.reactive.handler.AbstractUrlHandlerMapping;
 import org.springframework.web.reactive.handler.SimpleUrlHandlerMapping;
+import org.springframework.web.reactive.resource.ResourceTransformerSupport;
+import org.springframework.web.reactive.resource.ResourceUrlProvider;
 import org.springframework.web.reactive.resource.ResourceWebHandler;
 import org.springframework.web.server.WebHandler;
 
@@ -49,6 +51,7 @@ import org.springframework.web.server.WebHandler;
  * period for served resources.
  *
  * @author Rossen Stoyanchev
+ * @author Brian Clozel
  * @since 5.0
  */
 public class ResourceHandlerRegistry {
@@ -57,7 +60,10 @@ public class ResourceHandlerRegistry {
 
 	private final List<ResourceHandlerRegistration> registrations = new ArrayList<>();
 
-	private int order = Ordered.LOWEST_PRECEDENCE -1;
+	private int order = Ordered.LOWEST_PRECEDENCE - 1;
+
+	@Nullable
+	private ResourceUrlProvider resourceUrlProvider;
 
 
 	/**
@@ -69,6 +75,17 @@ public class ResourceHandlerRegistry {
 		this.resourceLoader = resourceLoader;
 	}
 
+	/**
+	 * Configure the {@link ResourceUrlProvider} that can be used by
+	 * {@link org.springframework.web.reactive.resource.ResourceTransformer} instances.
+	 * @param resourceUrlProvider the resource URL provider to use
+	 * @since 5.1.2
+	 */
+	public void setResourceUrlProvider(@Nullable ResourceUrlProvider resourceUrlProvider) {
+		this.resourceUrlProvider = resourceUrlProvider;
+	}
+
+
 
 	/**
 	 * Add a resource handler for serving static resources based on the specified
@@ -121,6 +138,11 @@ public class ResourceHandlerRegistry {
 		for (ResourceHandlerRegistration registration : this.registrations) {
 			for (String pathPattern : registration.getPathPatterns()) {
 				ResourceWebHandler handler = registration.getRequestHandler();
+				handler.getResourceTransformers().forEach(transformer -> {
+					if (transformer instanceof ResourceTransformerSupport) {
+						((ResourceTransformerSupport) transformer).setResourceUrlProvider(this.resourceUrlProvider);
+					}
+				});
 				try {
 					handler.afterPropertiesSet();
 				}

spring-webflux/src/main/java/org/springframework/web/reactive/config/WebFluxConfigurationSupport.java

@@ -55,6 +55,7 @@ import org.springframework.web.reactive.function.server.support.RouterFunctionMa
 import org.springframework.web.reactive.function.server.support.ServerResponseResultHandler;
 import org.springframework.web.reactive.handler.AbstractHandlerMapping;
 import org.springframework.web.reactive.handler.WebFluxResponseStatusExceptionHandler;
+import org.springframework.web.reactive.resource.ResourceUrlProvider;
 import org.springframework.web.reactive.result.SimpleHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.ArgumentResolverConfigurer;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
@@ -74,6 +75,7 @@ import org.springframework.web.server.i18n.LocaleContextResolver;
  * <p>Import directly or extend and override protected methods to customize.
  *
  * @author Rossen Stoyanchev
+ * @author Brian Clozel
  * @since 5.0
  */
 public class WebFluxConfigurationSupport implements ApplicationContextAware {
@@ -229,6 +231,7 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 			resourceLoader = new DefaultResourceLoader();
 		}
 		ResourceHandlerRegistry registry = new ResourceHandlerRegistry(resourceLoader);
+		registry.setResourceUrlProvider(resourceUrlProvider());
 		addResourceHandlers(registry);
 
 		AbstractHandlerMapping handlerMapping = registry.getHandlerMapping();
@@ -249,6 +252,11 @@ public class WebFluxConfigurationSupport implements ApplicationContextAware {
 		return handlerMapping;
 	}
 
+	@Bean
+	public ResourceUrlProvider resourceUrlProvider() {
+		return new ResourceUrlProvider();
+	}
+
 	/**
 	 * Override this method to add resource handlers for serving static resources.
 	 * @see ResourceHandlerRegistry

spring-webflux/src/test/java/org/springframework/web/reactive/config/ResourceHandlerRegistryTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -43,6 +43,8 @@ import org.springframework.web.reactive.resource.CssLinkResourceTransformer;
 import org.springframework.web.reactive.resource.PathResourceResolver;
 import org.springframework.web.reactive.resource.ResourceResolver;
 import org.springframework.web.reactive.resource.ResourceTransformer;
+import org.springframework.web.reactive.resource.ResourceTransformerSupport;
+import org.springframework.web.reactive.resource.ResourceUrlProvider;
 import org.springframework.web.reactive.resource.ResourceWebHandler;
 import org.springframework.web.reactive.resource.VersionResourceResolver;
 import org.springframework.web.reactive.resource.WebJarsResourceResolver;
@@ -120,8 +122,11 @@ public class ResourceHandlerRegistryTests {
 
 	@Test
 	public void resourceChain() throws Exception {
+		ResourceUrlProvider resourceUrlProvider = Mockito.mock(ResourceUrlProvider.class);
+		this.registry.setResourceUrlProvider(resourceUrlProvider);
 		ResourceResolver mockResolver = Mockito.mock(ResourceResolver.class);
-		ResourceTransformer mockTransformer = Mockito.mock(ResourceTransformer.class);
+		ResourceTransformerSupport mockTransformer = Mockito.mock(ResourceTransformerSupport.class);
+		
 		this.registration.resourceChain(true).addResolver(mockResolver).addTransformer(mockTransformer);
 
 		ResourceWebHandler handler = getHandler("/resources/**");
@@ -138,6 +143,7 @@ public class ResourceHandlerRegistryTests {
 		assertThat(transformers, Matchers.hasSize(2));
 		assertThat(transformers.get(0), Matchers.instanceOf(CachingResourceTransformer.class));
 		assertThat(transformers.get(1), Matchers.equalTo(mockTransformer));
+		Mockito.verify(mockTransformer).setResourceUrlProvider(resourceUrlProvider);
 	}
 
 	@Test

spring-webflux/src/test/java/org/springframework/web/reactive/config/WebFluxConfigurationSupportTests.java

@@ -60,6 +60,7 @@ import org.springframework.web.method.HandlerTypePredicate;
 import org.springframework.web.reactive.accept.RequestedContentTypeResolver;
 import org.springframework.web.reactive.handler.AbstractUrlHandlerMapping;
 import org.springframework.web.reactive.handler.SimpleUrlHandlerMapping;
+import org.springframework.web.reactive.resource.ResourceUrlProvider;
 import org.springframework.web.reactive.result.method.RequestMappingInfo;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerAdapter;
 import org.springframework.web.reactive.result.method.annotation.RequestMappingHandlerMapping;
@@ -285,6 +286,15 @@ public class WebFluxConfigurationSupportTests {
 		assertNotNull(webHandler);
 	}
 
+	@Test
+	public void resourceUrlProvider() throws Exception {
+		ApplicationContext context = loadConfig(WebFluxConfig.class);
+
+		String name = "resourceUrlProvider";
+		ResourceUrlProvider resourceUrlProvider = context.getBean(name, ResourceUrlProvider.class);
+		assertNotNull(resourceUrlProvider);
+	}
+
 
 	private void assertHasMessageReader(List<HttpMessageReader<?>> readers, ResolvableType type, MediaType mediaType) {
 		assertTrue(readers.stream().anyMatch(c -> mediaType == null || c.canRead(type, mediaType)));