Fix CachingResourceResolver key generation

When used in combination with GzipResourceResolver, the
CachingResourceResolver does not properly cache results, since it only
takes the request path as a input for cache key generation.

Here's an example of that behavior:

1. an HTTP client requests a resource with `Accept-Encoding: gzip`, so
the GzipResourceResolver can resolve a gzipped resource.
2. the configured CachingResourceResolver caches that resource.
3. another HTTP client requests the same resource, but it does not
support gzip encoding; the previously cached gzipped resource is still
returned.

This commit uses the presence/absence of gzip encoding support as an
input in cache keys generation.

Issue: SPR-12982

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -30,6 +30,7 @@ import org.springframework.util.Assert;
  * delegates to the resolver chain and saves the result in the cache.
  *
  * @author Rossen Stoyanchev
+ * @author Brian Clozel
  * @since 4.1
  */
 public class CachingResourceResolver extends AbstractResourceResolver {
@@ -61,7 +62,7 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 	protected Resource resolveResourceInternal(HttpServletRequest request, String requestPath,
 			List<? extends Resource> locations, ResourceResolverChain chain) {
 
-		String key = RESOLVED_RESOURCE_CACHE_KEY_PREFIX + requestPath;
+		String key = computeKey(request, requestPath);
 		Resource resource = this.cache.get(key, Resource.class);
 
 		if (resource != null) {
@@ -82,6 +83,18 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 		return resource;
 	}
 
+	protected String computeKey(HttpServletRequest request, String requestPath) {
+		StringBuilder key = new StringBuilder(RESOLVED_RESOURCE_CACHE_KEY_PREFIX);
+		key.append(requestPath);
+		if(request != null) {
+			String encoding = request.getHeader("Accept-Encoding");
+			if(encoding != null && encoding.contains("gzip")) {
+				key.append("+encoding=gzip");
+			}
+		}
+		return key.toString();
+	}
+
 	@Override
 	protected String resolveUrlPathInternal(String resourceUrlPath,
 			List<? extends Resource> locations, ResourceResolverChain chain) {

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/CachingResourceResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -27,6 +27,7 @@ import org.springframework.cache.Cache;
 import org.springframework.cache.concurrent.ConcurrentMapCache;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.Resource;
+import org.springframework.mock.web.test.MockHttpServletRequest;
 
 import static org.junit.Assert.*;
 
@@ -108,4 +109,42 @@ public class CachingResourceResolverTests {
 		assertNull(this.chain.resolveUrlPath("invalid.css", this.locations));
 	}
 
+	@Test
+	public void resolveResourceAcceptEncodingInCacheKey() {
+		String file = "bar.css";
+
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", file);
+		request.addHeader("Accept-Encoding", "gzip");
+		Resource expected = this.chain.resolveResource(request, file, this.locations);
+		String cacheKey = CachingResourceResolver.RESOLVED_RESOURCE_CACHE_KEY_PREFIX + file + "+encoding=gzip";
+
+		assertEquals(expected, this.cache.get(cacheKey).get());
+	}
+
+	@Test
+	public void resolveResourceNoAcceptEncodingInCacheKey() {
+		String file = "bar.css";
+
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", file);
+		Resource expected = this.chain.resolveResource(request, file, this.locations);
+		String cacheKey = CachingResourceResolver.RESOLVED_RESOURCE_CACHE_KEY_PREFIX + file;
+
+		assertEquals(expected, this.cache.get(cacheKey).get());
+	}
+
+	@Test
+	public void resolveResourceMatchingEncoding() {
+		Resource resource = Mockito.mock(Resource.class);
+		Resource gzResource = Mockito.mock(Resource.class);
+		this.cache.put(CachingResourceResolver.RESOLVED_RESOURCE_CACHE_KEY_PREFIX + "bar.css", resource);
+		this.cache.put(CachingResourceResolver.RESOLVED_RESOURCE_CACHE_KEY_PREFIX + "bar.css+encoding=gzip", gzResource);
+
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", "bar.css");
+		assertSame(resource, this.chain.resolveResource(request,"bar.css", this.locations));
+
+		request = new MockHttpServletRequest("GET", "bar.css");
+		request.addHeader("Accept-Encoding", "gzip");
+		assertSame(gzResource, this.chain.resolveResource(request, "bar.css", this.locations));
+	}
+
 }

spring-webmvc/src/test/java/org/springframework/web/servlet/resource/GzipResourceResolverTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2013 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -28,6 +28,8 @@ import org.junit.Before;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
+import org.springframework.cache.Cache;
+import org.springframework.cache.concurrent.ConcurrentMapCache;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.Resource;
@@ -38,6 +40,8 @@ import static org.junit.Assert.*;
 
 
 /**
+ * Unit tests for
+ * {@link org.springframework.web.servlet.resource.GzipResourceResolver}.
  *
  * @author Jeremy Grelle
  */
@@ -47,6 +51,8 @@ public class GzipResourceResolverTests {
 
 	private List<Resource> locations;
 
+	private Cache cache;
+
 	@BeforeClass
 	public static void createGzippedResources() throws IOException {
 		Resource location = new ClassPathResource("test/", GzipResourceResolverTests.class);
@@ -71,12 +77,15 @@ public class GzipResourceResolverTests {
 
 	@Before
 	public void setUp() {
+		this.cache = new ConcurrentMapCache("resourceCache");
+
 		Map<String, VersionStrategy> versionStrategyMap = new HashMap<>();
 		versionStrategyMap.put("/**", new ContentVersionStrategy());
 		VersionResourceResolver versionResolver = new VersionResourceResolver();
 		versionResolver.setStrategyMap(versionStrategyMap);
 
 		List<ResourceResolver> resolvers = new ArrayList<ResourceResolver>();
+		resolvers.add(new CachingResourceResolver(this.cache));
 		resolvers.add(new GzipResourceResolver());
 		resolvers.add(versionResolver);
 		resolvers.add(new PathResourceResolver());
@@ -96,7 +105,7 @@ public class GzipResourceResolverTests {
 		Resource resolved = resolver.resolveResource(request, file, locations);
 
 		assertEquals(resource.getDescription(), resolved.getDescription());
-		assertEquals(new ClassPathResource("test/"+file).getFilename(), resolved.getFilename());
+		assertEquals(new ClassPathResource("test/" + file).getFilename(), resolved.getFilename());
 		assertTrue("Expected " + resolved + " to be of type " + EncodedResource.class,
 				resolved instanceof EncodedResource);
 	}
@@ -115,4 +124,29 @@ public class GzipResourceResolverTests {
 		assertTrue("Expected " + resolved + " to be of type " + EncodedResource.class,
 				resolved instanceof EncodedResource);
 	}
+
+	@Test
+	public void resolveFromCacheWithEncodingVariants() throws IOException {
+		MockHttpServletRequest request = new MockHttpServletRequest("GET", "/js/foo.js");
+		request.addHeader("Accept-Encoding", "gzip");
+		String file = "js/foo.js";
+		String gzFile = file+".gz";
+		Resource resource = new ClassPathResource("test/"+file, getClass());
+		Resource gzResource = new ClassPathResource("test/"+gzFile, getClass());
+
+		// resolved resource is now cached in CachingResourceResolver
+		Resource resolved = resolver.resolveResource(request, file, locations);
+
+		assertEquals(gzResource.getDescription(), resolved.getDescription());
+		assertEquals(new ClassPathResource("test/" + file).getFilename(), resolved.getFilename());
+		assertTrue("Expected " + resolved + " to be of type " + EncodedResource.class,
+				resolved instanceof EncodedResource);
+
+		request = new MockHttpServletRequest("GET", "/js/foo.js");
+		resolved = resolver.resolveResource(request, file, locations);
+		assertEquals(resource.getDescription(), resolved.getDescription());
+		assertEquals(new ClassPathResource("test/" + file).getFilename(), resolved.getFilename());
+		assertFalse("Expected " + resolved + " to *not* be of type " + EncodedResource.class,
+				resolved instanceof EncodedResource);
+	}
 }