Resolve ResourceUrlProvider from current request

This commit changes `ResourceTransformerSupport` to look for the
`ResourceUrlProvider` in the current request if none is configured on
the resource transformer itself.

Issue: SPR-15369

spring-webflux/src/main/java/org/springframework/web/reactive/resource/AppCacheManifestTransformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -144,7 +144,7 @@ public class AppCacheManifestTransformer extends ResourceTransformerSupport {
 			return Mono.just(new LineOutput(info.getLine(), null));
 		}
 
-		String link = toAbsolutePath(info.getLine(), exchange.getRequest());
+		String link = toAbsolutePath(info.getLine(), exchange);
 		Mono<String> pathMono = resolveUrlPath(link, exchange, resource, chain)
 				.doOnNext(path -> {
 					if (logger.isTraceEnabled()) {

spring-webflux/src/main/java/org/springframework/web/reactive/resource/CssLinkResourceTransformer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -103,7 +103,7 @@ public class CssLinkResourceTransformer extends ResourceTransformerSupport {
 							.concatMap(segment -> {
 								String segmentContent = segment.getContent(fullContent);
 								if (segment.isLink() && !hasScheme(segmentContent)) {
-									String link = toAbsolutePath(segmentContent, exchange.getRequest());
+									String link = toAbsolutePath(segmentContent, exchange);
 									return resolveUrlPath(link, exchange, newResource, transformerChain)
 											.defaultIfEmpty(segmentContent);
 								}

spring-webflux/src/main/java/org/springframework/web/reactive/resource/ResourceTransformerSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -89,11 +89,11 @@ public abstract class ResourceTransformerSupport implements ResourceTransformer
 	 * The resulting path is also cleaned from sequences like "path/..".
 	 *
 	 * @param path the relative path to transform
-	 * @param request the referer request
+	 * @param exchange the current exchange
 	 * @return the absolute request path for the given resource path
 	 */
-	protected String toAbsolutePath(String path, ServerHttpRequest request) {
-		String requestPath = request.getURI().getPath();
+	protected String toAbsolutePath(String path, ServerWebExchange exchange) {
+		String requestPath = exchange.getRequest().getURI().getPath();
 		String absolutePath = StringUtils.applyRelativePath(requestPath, path);
 		return StringUtils.cleanPath(absolutePath);
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/resource/ResourceTransformerSupport.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2017 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.
@@ -38,15 +38,8 @@ public abstract class ResourceTransformerSupport implements ResourceTransformer
 	/**
 	 * Configure a {@link ResourceUrlProvider} to use when resolving the public
 	 * URL of links in a transformed resource (e.g. import links in a CSS file).
-	 * This is required only for links expressed as full paths, i.e. including
-	 * context and servlet path, and not for relative links.
-	 * <p>By default this property is not set. In that case if a
-	 * {@code ResourceUrlProvider} is needed an attempt is made to find the
-	 * {@code ResourceUrlProvider} exposed through the
-	 * {@link org.springframework.web.servlet.resource.ResourceUrlProviderExposingInterceptor
-	 * ResourceUrlProviderExposingInterceptor} (configured by default in the MVC
-	 * Java config and XML namespace). Therefore explicitly configuring this
-	 * property should not be needed in most cases.
+	 * This is required only for links expressed as full paths and not for
+	 * relative links.
 	 * @param resourceUrlProvider the URL provider to use
 	 */
 	public void setResourceUrlProvider(ResourceUrlProvider resourceUrlProvider) {
@@ -96,7 +89,7 @@ public abstract class ResourceTransformerSupport implements ResourceTransformer
 	 * @return the absolute request path for the given resource path
 	 */
 	protected String toAbsolutePath(String path, HttpServletRequest request) {
-		String requestPath = this.getResourceUrlProvider().getUrlPathHelper().getRequestUri(request);
+		String requestPath = this.findResourceUrlProvider(request).getUrlPathHelper().getRequestUri(request);
 		String absolutePath = StringUtils.applyRelativePath(requestPath, path);
 		return StringUtils.cleanPath(absolutePath);
 	}