/*
* eXist Open Source Native XML Database
* Copyright (C) 2010-2012 The eXist Project
* http://exist-db.org
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*
* $Id$
*/
package org.exist.collections.triggers;
import java.util.HashMap;
import java.util.Map;
import javax.xml.transform.Templates;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.sax.SAXTransformerFactory;
import javax.xml.transform.sax.TemplatesHandler;
import org.apache.log4j.Logger;
import org.exist.dom.DocumentImpl;
import org.exist.storage.DBBroker;
import org.exist.storage.serializers.Serializer;
import org.exist.xmldb.XmldbURI;
import org.xml.sax.SAXException;
/**
* Cache for STX Templates
*
* @author aretter
*/
public class STXTemplatesCache {
protected Logger LOG = Logger.getLogger(getClass());
private Map<XmldbURI, CachedTemplate> cache = new HashMap<XmldbURI, CachedTemplate>();
private final SAXTransformerFactory factory = (SAXTransformerFactory)TransformerFactory.newInstance("net.sf.joost.trax.TransformerFactoryImpl", getClass().getClassLoader());
/**
* Will get the compiled stylesheet from the cache
*
* If the stylesheet is not present in the cache it will be compiled and added to the cache
*
* If the stylesheet is in the cache but older than the current stylesheet it will be re-compiled and cached
*
* @param broker Database broker for accessing the serializer pool
* @return The compiled stylesheet
*/
public synchronized Templates getOrUpdateTemplate(DBBroker broker, DocumentImpl stylesheet) throws TransformerConfigurationException, SAXException {
//is it already in the cache
final XmldbURI stylesheetUri = stylesheet.getURI();
final long lastModified = stylesheet.getMetadata().getLastModified();
CachedTemplate cachedTemplate = cache.get(stylesheetUri);
if(cachedTemplate == null) {
cachedTemplate = storeInCache(broker, stylesheetUri, stylesheet, lastModified);
} else {
//has it been modified since it was cached?
if(lastModified > cachedTemplate.getLastUpdated()) {
//refresh the entry in the cache
cachedTemplate = storeInCache(broker, stylesheetUri, stylesheet, lastModified);
}
}
LOG.debug("Retrieved STX Template '" + stylesheetUri.toString() + "' from cache.");
return cachedTemplate.getTemplate();
}
private CachedTemplate storeInCache(DBBroker broker, XmldbURI stylesheetUri, DocumentImpl stylesheet, long lastModified) throws TransformerConfigurationException, SAXException {
final Templates compiled = compileTemplate(broker, stylesheet);
final CachedTemplate cachedTemplate = new CachedTemplate(compiled, lastModified);
cache.put(stylesheetUri, cachedTemplate);
LOG.debug("Compiled and Stored STX Template '" + stylesheetUri.toString() + "' in cache.");
return cachedTemplate;
}
private Templates compileTemplate(DBBroker broker, DocumentImpl stylesheet) throws TransformerConfigurationException, SAXException {
final Serializer serializer = broker.getSerializer();
final TemplatesHandler thandler = factory.newTemplatesHandler();
serializer.setSAXHandlers(thandler, null);
serializer.toSAX(stylesheet);
return thandler.getTemplates();
}
private class CachedTemplate {
private final Templates templates;
private final long lastUpdated;
public CachedTemplate(Templates templates, long lastUpdated) {
this.templates = templates;
this.lastUpdated = lastUpdated;
}
private long getLastUpdated() {
return lastUpdated;
}
private Templates getTemplate() {
return templates;
}
}
}