Add CachingResourceResolver

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

@@ -0,0 +1,106 @@
+/*
+ * Copyright 2002-2014 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.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.web.servlet.resource;
+
+import org.springframework.cache.Cache;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+import javax.servlet.http.HttpServletRequest;
+import java.util.List;
+
+/**
+ * A {@link org.springframework.web.servlet.resource.ResourceResolver} that
+ * resolves resources from a {@link org.springframework.cache.Cache} or otherwise
+ * delegates to the resolver chain and saves the result in the cache.
+ *
+ * @author Rossen Stoyanchev
+ * @since 4.1
+ */
+public class CachingResourceResolver extends AbstractResourceResolver {
+
+	private static final String REQUEST_PATH_PREFIX = "requestPath:";
+
+	private static final String RESOURCE_URL_PATH_PREFIX = "resourceUrlPath:";
+
+
+	private final Cache cache;
+
+
+	public CachingResourceResolver(Cache cache) {
+		Assert.notNull(cache, "'cache' is required");
+		this.cache = cache;
+	}
+
+	/**
+	 * Return the configured {@code Cache}.
+	 */
+	public Cache getCache() {
+		return this.cache;
+	}
+
+	@Override
+	protected Resource resolveResourceInternal(HttpServletRequest request, String requestPath,
+			List<? extends Resource> locations, ResourceResolverChain chain) {
+
+		String key = REQUEST_PATH_PREFIX + requestPath;
+		Resource resource = this.cache.get(key, Resource.class);
+
+		if (resource != null) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Found match");
+			}
+			return resource;
+		}
+
+		resource = chain.resolveResource(request, requestPath, locations);
+		if (resource != null) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Putting resolved resource in cache");
+			}
+			this.cache.put(key, resource);
+		}
+
+		return resource;
+	}
+
+	@Override
+	protected String resolveUrlPathInternal(String resourceUrlPath,
+			List<? extends Resource> locations, ResourceResolverChain chain) {
+
+		String key = RESOURCE_URL_PATH_PREFIX + resourceUrlPath;
+		String resolvedUrlPath = this.cache.get(key, String.class);
+
+		if (resolvedUrlPath != null) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Found match");
+			}
+			return resolvedUrlPath;
+		}
+
+		resolvedUrlPath = chain.resolveUrlPath(resourceUrlPath, locations);
+		if (resolvedUrlPath != null) {
+			if (logger.isTraceEnabled()) {
+				logger.trace("Putting resolved resource URL path in cache");
+			}
+			this.cache.put(key, resolvedUrlPath);
+		}
+
+		return resolvedUrlPath;
+	}
+
+}