CachingResourceResolver varies by known codings only

Issue: SPR-16381

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

@@ -16,7 +16,9 @@
 
 package org.springframework.web.servlet.resource;
 
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.List;
 import java.util.stream.Collectors;
 import javax.servlet.http.HttpServletRequest;
@@ -47,6 +49,8 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 
 	private final Cache cache;
 
+	private final List<String> contentCodings = new ArrayList<>(EncodedResourceResolver.DEFAULT_CODINGS);
+
 
 	public CachingResourceResolver(Cache cache) {
 		Assert.notNull(cache, "Cache is required");
@@ -69,6 +73,33 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 		return this.cache;
 	}
 
+	/**
+	 * Configure the supported content codings from the
+	 * {@literal "Accept-Encoding"} header for which to cache resource variations.
+	 *
+	 * <p>The codings configured here are generally expected to match those
+	 * configured on {@link EncodedResourceResolver#setContentCodings(List)}.
+	 *
+	 * <p>By default this property is set to {@literal ["br", "gzip"]} based on
+	 * the value of {@link EncodedResourceResolver#DEFAULT_CODINGS}.
+	 *
+	 * @param codings one or more supported content codings
+	 * @since 5.1
+	 */
+	public void setContentCodings(List<String> codings) {
+		Assert.notEmpty(codings, "At least one content coding expected.");
+		this.contentCodings.clear();
+		this.contentCodings.addAll(codings);
+	}
+
+	/**
+	 * Return a read-only list with the supported content codings.
+	 * @since 5.1
+	 */
+	public List<String> getContentCodings() {
+		return Collections.unmodifiableList(this.contentCodings);
+	}
+
 
 	@Override
 	protected Resource resolveResourceInternal(@Nullable HttpServletRequest request, String requestPath,
@@ -100,7 +131,7 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 		key.append(requestPath);
 		if (request != null) {
 			String codingKey = getContentCodingKey(request);
-			if (codingKey != null) {
+			if (StringUtils.hasText(codingKey)) {
 				key.append("+encoding=").append(codingKey);
 			}
 		}
@@ -108,7 +139,7 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 	}
 
 	@Nullable
-	private static String getContentCodingKey(HttpServletRequest request) {
+	private String getContentCodingKey(HttpServletRequest request) {
 		String header = request.getHeader(HttpHeaders.ACCEPT_ENCODING);
 		if (!StringUtils.hasText(header)) {
 			return null;
@@ -118,8 +149,7 @@ public class CachingResourceResolver extends AbstractResourceResolver {
 					int index = token.indexOf(';');
 					return (index >= 0 ? token.substring(0, index) : token).trim().toLowerCase();
 				})
-				.filter(coding -> !coding.equals("*"))
-				.filter(coding -> !coding.equals("identity"))
+				.filter(this.contentCodings::contains)
 				.sorted()
 				.collect(Collectors.joining(","));
 	}

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

@@ -53,7 +53,10 @@ import org.springframework.util.Assert;
  */
 public class EncodedResourceResolver extends AbstractResourceResolver {
 
-	private final List<String> contentCodings = new ArrayList<>(Arrays.asList("br", "gzip"));
+	public static final List<String> DEFAULT_CODINGS = Arrays.asList("br", "gzip");
+
+
+	private final List<String> contentCodings = new ArrayList<>(DEFAULT_CODINGS);
 
 	private final Map<String, String> extensions = new LinkedHashMap<>();
 
@@ -71,11 +74,15 @@ public class EncodedResourceResolver extends AbstractResourceResolver {
 	 * is used.
 	 *
 	 * <p><strong>Note:</strong> Each coding must be associated with a file
-	 * extension via {@link #registerExtension} or {@link #setExtensions}.
+	 * extension via {@link #registerExtension} or {@link #setExtensions}. Also
+	 * customizations to the list of codings here should be matched by
+	 * customizations to the same list in {@link CachingResourceResolver} to
+	 * ensure encoded variants of a resource are cached under separate keys.
 	 *
 	 * <p>By default this property is set to {@literal ["br", "gzip"]}.
 	 *
 	 * @param codings one or more supported content codings
+	 * @since 5.1
 	 */
 	public void setContentCodings(List<String> codings) {
 		Assert.notEmpty(codings, "At least one content coding expected.");
@@ -85,6 +92,7 @@ public class EncodedResourceResolver extends AbstractResourceResolver {
 
 	/**
 	 * Return a read-only list with the supported content codings.
+	 * @since 5.1
 	 */
 	public List<String> getContentCodings() {
 		return Collections.unmodifiableList(this.contentCodings);
@@ -97,6 +105,7 @@ public class EncodedResourceResolver extends AbstractResourceResolver {
 	 * {@literal ["gzip" -> ".gz"]}.
 	 * @param extensions the extensions to use.
 	 * @see #registerExtension(String, String)
+	 * @since 5.1
 	 */
 	public void setExtensions(Map<String, String> extensions) {
 		extensions.forEach(this::registerExtension);
@@ -106,6 +115,7 @@ public class EncodedResourceResolver extends AbstractResourceResolver {
 	 * Java config friendly alternative to {@link #setExtensions(Map)}.
 	 * @param coding the content coding
 	 * @param extension the associated file extension
+	 * @since 5.1
 	 */
 	public void registerExtension(String coding, String extension) {
 		this.extensions.put(coding, extension.startsWith(".") ? extension : "." + extension);
@@ -113,6 +123,7 @@ public class EncodedResourceResolver extends AbstractResourceResolver {
 
 	/**
 	 * Return a read-only map with coding-to-extension mappings.
+	 * @since 5.1
 	 */
 	public Map<String, String> getExtensions() {
 		return Collections.unmodifiableMap(this.extensions);