plugins/osgi/src/main/java/org/apache/struts2/osgi/BundleFreemarkerManager.java

/*
 * 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.struts2.osgi;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.LogManager;
import freemarker.cache.ClassTemplateLoader;
import freemarker.cache.FileTemplateLoader;
import freemarker.cache.MultiTemplateLoader;
import freemarker.cache.TemplateLoader;
import freemarker.cache.WebappTemplateLoader;
import org.apache.struts2.osgi.loaders.FreeMarkerBundleResourceLoader;
import org.apache.struts2.views.freemarker.FreemarkerManager;
import org.apache.struts2.views.freemarker.StrutsClassTemplateLoader;

import javax.servlet.ServletContext;
import java.io.File;
import java.io.IOException;
import java.net.URI;

/**
 * This class extends FreemarkerManager in core to add a template loader
 * (that finds resources inside bundles) to MultiTemplateLoader
 */
public class BundleFreemarkerManager extends FreemarkerManager {

    private static final Logger LOG = LogManager.getLogger(BundleFreemarkerManager.class);

    @Override
    protected TemplateLoader createTemplateLoader(ServletContext servletContext, String templatePath) {
        TemplateLoader templatePathLoader = null;

        if (servletContext == null) {
            throw new IllegalArgumentException("Unable to create a template loader using a null servlet context");  // Better than a NPE.
        }

        try {
             if (templatePath != null && templatePath.startsWith("class://")) {
                 // substring(7) is intentional as we "reuse" the last slash
                 templatePathLoader = new ClassTemplateLoader(getClass(), templatePath.substring(7));
             } else if (templatePath != null && templatePath.startsWith("file://")) {
                 templatePathLoader = new FileTemplateLoader(new File(URI.create(templatePath)));
             } else {
                 LOG.warn("The provided template path specified: [{}] does not start with expected path protocol (class: or file:).  " +
                          "The template loader will only look in standard locations", templatePath);
             }
         } catch (IOException e) {
             LOG.error("Invalid template path specified: [{}]", e.getMessage(), e);
         }

        // presume that most apps will require the class and webapp template loader
        // if people wish to
        return templatePathLoader != null ?
                new MultiTemplateLoader(new TemplateLoader[]{
                        templatePathLoader,
                        new WebappTemplateLoader(servletContext),
                        new StrutsClassTemplateLoader(),
                        new FreeMarkerBundleResourceLoader()
                })
                : new MultiTemplateLoader(new TemplateLoader[]{
                new WebappTemplateLoader(servletContext),
                new StrutsClassTemplateLoader(),
                new FreeMarkerBundleResourceLoader()
        });
    }

}