Allow custom instances of WebJarAssetLocator

This commit allows to configure a custom WebJarAssetLocator in
WebJarResourceResolvers.

Issue: SPR-14092

spring-webmvc/src/main/java/org/springframework/web/servlet/config/annotation/ResourceChainRegistration.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -56,6 +56,8 @@ public class ResourceChainRegistration {
 
 	private boolean hasCssLinkTransformer;
 
+	private boolean hasWebjarsResolver;
+
 
 	public ResourceChainRegistration(boolean cacheResources) {
 		this(cacheResources, cacheResources ? new ConcurrentMapCache(DEFAULT_CACHE_NAME) : null);
@@ -84,6 +86,9 @@ public class ResourceChainRegistration {
 		else if (resolver instanceof PathResourceResolver) {
 			this.hasPathResolver = true;
 		}
+		else if (resolver instanceof WebJarsResourceResolver) {
+			this.hasWebjarsResolver = true;
+		}
 		return this;
 	}
 
@@ -104,7 +109,7 @@ public class ResourceChainRegistration {
 	protected List<ResourceResolver> getResourceResolvers() {
 		if (!this.hasPathResolver) {
 			List<ResourceResolver> result = new ArrayList<ResourceResolver>(this.resolvers);
-			if (isWebJarsAssetLocatorPresent) {
+			if (isWebJarsAssetLocatorPresent && !this.hasWebjarsResolver) {
 				result.add(new WebJarsResourceResolver());
 			}
 			result.add(new PathResourceResolver());
@@ -114,7 +119,7 @@ public class ResourceChainRegistration {
 	}
 
 	protected List<ResourceTransformer> getResourceTransformers() {
-		if (this.hasVersionResolver  && !this.hasCssLinkTransformer) {
+		if (this.hasVersionResolver && !this.hasCssLinkTransformer) {
 			List<ResourceTransformer> result = new ArrayList<ResourceTransformer>(this.transformers);
 			boolean hasTransformers = !this.transformers.isEmpty();
 			boolean hasCaching = hasTransformers && this.transformers.get(0) instanceof CachingResourceTransformer;

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

@@ -17,6 +17,7 @@
 package org.springframework.web.servlet.resource;
 
 import java.util.List;
+
 import javax.servlet.http.HttpServletRequest;
 
 import org.webjars.MultipleMatchesException;
@@ -49,8 +50,23 @@ public class WebJarsResourceResolver extends AbstractResourceResolver {
 
 	private final static int WEBJARS_LOCATION_LENGTH = WEBJARS_LOCATION.length();
 
-	private final WebJarAssetLocator webJarAssetLocator = new WebJarAssetLocator();
+	private final WebJarAssetLocator webJarAssetLocator;
 
+	/**
+	 * Create a {@code WebJarsResourceResolver} with a default {@code WebJarAssetLocator} instance.
+	 */
+	public WebJarsResourceResolver() {
+		this(new WebJarAssetLocator());
+	}
+
+	/**
+	 * Create a {@code WebJarsResourceResolver} with a custom {@code WebJarAssetLocator} instance,
+	 * e.g. with a custom index.
+	 * @since 4.3.0
+	 */
+	public WebJarsResourceResolver(WebJarAssetLocator webJarAssetLocator) {
+		this.webJarAssetLocator = webJarAssetLocator;
+	}
 
 	@Override
 	protected Resource resolveResourceInternal(HttpServletRequest request, String requestPath,

spring-webmvc/src/test/java/org/springframework/web/servlet/config/annotation/ResourceHandlerRegistryTests.java

@@ -180,6 +180,7 @@ public class ResourceHandlerRegistryTests {
 	public void resourceChainWithOverrides() throws Exception {
 		CachingResourceResolver cachingResolver = Mockito.mock(CachingResourceResolver.class);
 		VersionResourceResolver versionResolver = Mockito.mock(VersionResourceResolver.class);
+		WebJarsResourceResolver webjarsResolver = Mockito.mock(WebJarsResourceResolver.class);
 		PathResourceResolver pathResourceResolver = new PathResourceResolver();
 		CachingResourceTransformer cachingTransformer = Mockito.mock(CachingResourceTransformer.class);
 		AppCacheManifestTransformer appCacheTransformer = Mockito.mock(AppCacheManifestTransformer.class);
@@ -189,6 +190,7 @@ public class ResourceHandlerRegistryTests {
 				.resourceChain(false)
 					.addResolver(cachingResolver)
 					.addResolver(versionResolver)
+					.addResolver(webjarsResolver)
 					.addResolver(pathResourceResolver)
 					.addTransformer(cachingTransformer)
 					.addTransformer(appCacheTransformer)
@@ -196,10 +198,11 @@ public class ResourceHandlerRegistryTests {
 
 		ResourceHttpRequestHandler handler = getHandler("/resources/**");
 		List<ResourceResolver> resolvers = handler.getResourceResolvers();
-		assertThat(resolvers.toString(), resolvers, Matchers.hasSize(3));
+		assertThat(resolvers.toString(), resolvers, Matchers.hasSize(4));
 		assertThat(resolvers.get(0), Matchers.sameInstance(cachingResolver));
 		assertThat(resolvers.get(1), Matchers.sameInstance(versionResolver));
-		assertThat(resolvers.get(2), Matchers.sameInstance(pathResourceResolver));
+		assertThat(resolvers.get(2), Matchers.sameInstance(webjarsResolver));
+		assertThat(resolvers.get(3), Matchers.sameInstance(pathResourceResolver));
 
 		List<ResourceTransformer> transformers = handler.getResourceTransformers();
 		assertThat(transformers, Matchers.hasSize(3));