/**
* 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.solr.util.xslt;
import java.io.IOException;
import java.io.InputStream;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.commons.io.IOUtils;
import javax.xml.transform.Templates;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamSource;
import org.apache.solr.common.ResourceLoader;
import org.apache.solr.common.util.SystemIdResolver;
import org.apache.solr.common.util.XMLErrorLogger;
import org.apache.solr.core.SolrConfig;
/** Singleton that creates a Transformer for the XSLTServletFilter.
* For now, only caches the last created Transformer, but
* could evolve to use an LRU cache of Transformers.
*
* See http://www.javaworld.com/javaworld/jw-05-2003/jw-0502-xsl_p.html for
* one possible way of improving caching.
*/
public class TransformerProvider {
private String lastFilename;
private Templates lastTemplates = null;
private long cacheExpires = 0;
private static final Logger log = LoggerFactory.getLogger(TransformerProvider.class.getName());
private static final XMLErrorLogger xmllog = new XMLErrorLogger(log);
public static TransformerProvider instance = new TransformerProvider();
/** singleton */
private TransformerProvider() {
// tell'em: currently, we only cache the last used XSLT transform, and blindly recompile it
// once cacheLifetimeSeconds expires
log.warn(
"The TransformerProvider's simplistic XSLT caching mechanism is not appropriate "
+ "for high load scenarios, unless a single XSLT transform is used"
+ " and xsltCacheLifetimeSeconds is set to a sufficiently high value."
);
}
/** Return a new Transformer, possibly created from our cached Templates object
* @throws TransformerConfigurationException
*/
public synchronized Transformer getTransformer(SolrConfig solrConfig, String filename,int cacheLifetimeSeconds) throws IOException {
// For now, the Templates are blindly reloaded once cacheExpires is over.
// It'd be better to check the file modification time to reload only if needed.
if(lastTemplates!=null && filename.equals(lastFilename) && System.currentTimeMillis() < cacheExpires) {
if(log.isDebugEnabled()) {
log.debug("Using cached Templates:" + filename);
}
} else {
lastTemplates = getTemplates(solrConfig.getResourceLoader(), filename,cacheLifetimeSeconds);
}
Transformer result = null;
try {
result = lastTemplates.newTransformer();
} catch(TransformerConfigurationException tce) {
log.error(getClass().getName(), "getTransformer", tce);
final IOException ioe = new IOException("newTransformer fails ( " + lastFilename + ")");
ioe.initCause(tce);
throw ioe;
}
return result;
}
/** Return a Templates object for the given filename */
private Templates getTemplates(ResourceLoader loader, String filename,int cacheLifetimeSeconds) throws IOException {
Templates result = null;
lastFilename = null;
try {
if(log.isDebugEnabled()) {
log.debug("compiling XSLT templates:" + filename);
}
final String fn = "xslt/" + filename;
final TransformerFactory tFactory = TransformerFactory.newInstance();
tFactory.setURIResolver(new SystemIdResolver(loader).asURIResolver());
tFactory.setErrorListener(xmllog);
final StreamSource src = new StreamSource(loader.openResource(fn),
SystemIdResolver.createSystemIdFromResourceName(fn));
try {
result = tFactory.newTemplates(src);
} finally {
// some XML parsers are broken and don't close the byte stream (but they should according to spec)
IOUtils.closeQuietly(src.getInputStream());
}
} catch (Exception e) {
log.error(getClass().getName(), "newTemplates", e);
final IOException ioe = new IOException("Unable to initialize Templates '" + filename + "'");
ioe.initCause(e);
throw ioe;
}
lastFilename = filename;
lastTemplates = result;
cacheExpires = System.currentTimeMillis() + (cacheLifetimeSeconds * 1000);
return result;
}
}