TemplateIncludesCache.java

/*
 * Sewing: a Simple framework for Embedded-OSGi Web Development
 * Copyright (C) 2009 Bug Labs
 * Email: bballantine@buglabs.net
 * Site: http://www.buglabs.net
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA  02111-1307, USA.
 */

package com.buglabs.osgi.sewing;

import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Iterator;

import org.osgi.framework.BundleContext;
import org.osgi.service.log.LogService;

import freemarker.template.CacheListener;
import freemarker.template.InputSource;
import freemarker.template.Template;
import freemarker.template.cache.Cache;
import freemarker.template.cache.Cacheable;

/**
 * This class allows us to include templates within templates All included
 * templates must be in includesAlias the default extension for include
 * templates is "inc"
 * 
 * Only the minimum methods for Cache have been implemented, getItem(String) and
 * getItem(String, String)
 * 
 * This is all we need to allow simple <include "name"> directives in Sewing
 * freemarker templates
 * 
 * @author brian
 * 
 */
public class TemplateIncludesCache implements Cache {

	private static final String UNSUPPORTED_EXCEPTION_MESSAGE_ENDING = "is not supported for type " + TemplateIncludesCache.class.getName();
	private static final String DEFAULT_EXTENSION = "inc";

	private BundleContext bundle_context;
	private String includes_alias;

	public TemplateIncludesCache(BundleContext context, String includesAlias) {
		bundle_context = context;
		includes_alias = includesAlias;
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see freemarker.template.cache.Cache#getItem(java.lang.String)
	 */
	public Cacheable getItem(String name) {
		return getItem(name, DEFAULT_EXTENSION);
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see freemarker.template.cache.Cache#getItem(java.lang.String,
	 * java.lang.String)
	 */
	public Cacheable getItem(String name, String type) {
		String path = "/" + includes_alias + "/" + name + "." + type;
		URL templateUrl = bundle_context.getBundle().getResource(path);
		if (templateUrl == null) {
			LogManager.log(LogService.LOG_ERROR, "Failed to get item from input:" + path);
			return null;
		}
		
		InputSource inputSource;
		Template t = null;
		try {
			inputSource = new InputSource(new InputStreamReader(templateUrl.openStream()));
			t = new Template(inputSource);
		} catch (IOException e) {
			LogManager.log(LogService.LOG_ERROR, "Failed to get item from input.", e);
		}
		return t;
	}

	/*
	 * we just want to be able to include stuff from the includes folder so the
	 * following methods are not implemented
	 */

	/**
	 * Not implemented - throws UnsupportedOperationException
	 */
	public void addCacheListener(CacheListener listener) {
		throw new UnsupportedOperationException("addCacheListener" + UNSUPPORTED_EXCEPTION_MESSAGE_ENDING);
	}

	/**
	 * Not implemented - throws UnsupportedOperationException
	 */
	public CacheListener[] getCacheListeners() {
		throw new UnsupportedOperationException("addCacheListener" + UNSUPPORTED_EXCEPTION_MESSAGE_ENDING);
	}

	/**
	 * Not implemented - throws UnsupportedOperationException
	 */
	public Iterator listCachedFiles() {
		throw new UnsupportedOperationException("addCacheListener" + UNSUPPORTED_EXCEPTION_MESSAGE_ENDING);
	}

	/**
	 * Not implemented - throws UnsupportedOperationException
	 */
	public void removeCacheListener(CacheListener listener) {
		throw new UnsupportedOperationException("addCacheListener" + UNSUPPORTED_EXCEPTION_MESSAGE_ENDING);
	}

	/**
	 * Not implemented - throws UnsupportedOperationException
	 */
	public void stopAutoUpdate() {
		throw new UnsupportedOperationException("addCacheListener" + UNSUPPORTED_EXCEPTION_MESSAGE_ENDING);
	}

}