VersionedCSSDirective.java

/*
 * $HeadURL$
 * $Id$
 * Copyright (c) 2006-2012 by Public Library of Science http://plos.org http://ambraproject.org
 * 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-2.0Unless 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.ambraproject.util;

import freemarker.template.TemplateBooleanModel;
import freemarker.template.TemplateException;

import java.util.Map;

/**
 * Freemarker template that renders a link to a .css file.  In order to facilitate correct browser caching, a
 * fake parameter is appended to the end of the link with a checksum of the file's contents.  In this way, when the
 * file changes, the browser should request a new copy.
 * <p/>
 * See the superclass javadoc for further usage and implementation notes.
 */
public class VersionedCSSDirective extends VersionedFileDirective {

  @Override
  public String getLink(String filename, String fingerprint, Map params) throws TemplateException {
    Object mediaParam = params.get("media");
    String media = "";
    if (mediaParam != null) {
      media = "media=\"" + mediaParam.toString() + "\"";
    }
    return String.format("<link rel=\"stylesheet\" type=\"text/css\" %s href=\"%s?v=%s\" />\n", media, filename,
        fingerprint);
  }
}