Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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.apache.wicket.request.resource.caching; import java.util.regex.Pattern; import org.apache.wicket.request.cycle.RequestCycle; import org.apache.wicket.request.http.WebResponse; import org.apache.wicket.request.resource.AbstractResource; import org.apache.wicket.request.resource.caching.version.CachingResourceVersion; import org.apache.wicket.request.resource.caching.version.IResourceVersion; import org.apache.wicket.util.lang.Args; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * resource caching strategy that adds a version for the * requested resource to the filename. * <p/> * versioned_filename := [basename][version-prefix][version](.extension) * <p/> * the <code>version</code> must not contain the <code>version-prefix</code> so * please use an unambiguous value for the <code>version-prefix</code>. The default * <code>version-prefix</code> is <code>{@value #DEFAULT_VERSION_PREFIX}</code>. * <p/> * Since browsers and proxies use the versioned filename of the resource * as a cache key a change to the version will also change the filename and * cause a reliable cache miss. This enables us to set the caching duration * of the resource to a maximum and get best network performance. * <p/> * * @author Peter Ertl * * @since 1.5 */ public class FilenameWithVersionResourceCachingStrategy implements IResourceCachingStrategy { private static final Logger LOG = LoggerFactory.getLogger(FilenameWithVersionResourceCachingStrategy.class); private static final String DEFAULT_VERSION_PREFIX = "-ver-"; /** string that marks the beginning the of the version in the decorated filename */ private final String versionPrefix; /** resource version provider */ private final IResourceVersion resourceVersion; /** * create filename caching strategy with given version provider and * <code>version-prefix = '{@value #DEFAULT_VERSION_PREFIX}'</code> * * @param resourceVersion * version provider * * @see #FilenameWithVersionResourceCachingStrategy(String, org.apache.wicket.request.resource.caching.version.IResourceVersion) */ public FilenameWithVersionResourceCachingStrategy(IResourceVersion resourceVersion) { this(DEFAULT_VERSION_PREFIX, resourceVersion); } /** * Constructor * * @param versionPrefix * string that marks the beginning the of the version in the decorated filename * @param resourceVersion * resource version object * * @see #FilenameWithVersionResourceCachingStrategy(org.apache.wicket.request.resource.caching.version.IResourceVersion) */ public FilenameWithVersionResourceCachingStrategy(String versionPrefix, IResourceVersion resourceVersion) { this.resourceVersion = Args.notNull(resourceVersion, "resourceVersion"); this.versionPrefix = Args.notEmpty(versionPrefix, "versionPrefix"); } /** * @return string appended to the filename before the version string */ public final String getVersionPrefix() { return versionPrefix; } @Override public void decorateUrl(ResourceUrl url, IStaticCacheableResource resource) { // get version string for requested resource final String version = this.resourceVersion.getVersion(resource); // ignore resource if no version information is available if (version == null) { return; } // get undecorated filename final String filename = url.getFileName(); // check if resource name has extension final int extensionAt = filename.lastIndexOf('.'); // create filename with version: // // filename := // [basename][version-prefix][version](.extension) // final StringBuilder versionedFilename = new StringBuilder(); // add filename if (extensionAt == -1) { versionedFilename.append(filename); } else { versionedFilename.append(filename.substring(0, extensionAt)); } int pos = versionedFilename.indexOf(getVersionPrefix()); if (pos != -1 && isVersion(versionedFilename.substring(pos + versionPrefix.length()))) { LOG.error( "A resource with name '{}' contains the version prefix '{}' so the un-decoration will not work." + " Either use a different version prefix or rename this resource.", filename, getVersionPrefix()); } // add version suffix versionedFilename.append(versionPrefix); // add version versionedFilename.append(version); // add extension if present if (extensionAt != -1) { versionedFilename.append(filename.substring(extensionAt)); } // set versioned filename url.setFileName(versionedFilename.toString()); } @Override public void undecorateUrl(ResourceUrl url) { final String filename = url.getFileName(); // check for extension int pos = filename.lastIndexOf('.'); // get name of file without extension (but with version string) final String fullname = pos == -1 ? filename : filename.substring(0, pos); // get extension of file if present final String extension = pos == -1 ? null : filename.substring(pos); // get position of version string pos = fullname.lastIndexOf(versionPrefix); // remove version string if it exists if (pos != -1 && isVersion(fullname.substring(pos + versionPrefix.length()))) { // get filename before version string final String basename = fullname.substring(0, pos); // create filename without version string // (required for working resource lookup) url.setFileName(extension == null ? basename : basename + extension); // store the version in the request cycle RequestCycle requestCycle = RequestCycle.get(); if (requestCycle != null) { int idx = fullname.indexOf(versionPrefix); String urlVersion = fullname.substring(idx + versionPrefix.length()); requestCycle.setMetaData(URL_VERSION, urlVersion); } } } private boolean isVersion(String substring) { Pattern versionPattern = resourceVersion.getVersionPattern(); return versionPattern == null || versionPattern.matcher(substring).matches(); } /** * set resource caching to maximum and set cache-visibility to 'public' * * @param response */ @Override public void decorateResponse(AbstractResource.ResourceResponse response, IStaticCacheableResource resource) { String requestedVersion = RequestCycle.get().getMetaData(URL_VERSION); String calculatedVersion = this.resourceVersion.getVersion(resource); if (calculatedVersion != null && calculatedVersion.equals(requestedVersion)) { response.setCacheDurationToMaximum(); response.setCacheScope(WebResponse.CacheScope.PUBLIC); } } @Override public void clearCache() { if (resourceVersion instanceof CachingResourceVersion) { ((CachingResourceVersion) resourceVersion).invalidateAll(); } } }