org.apache.xml.utils.XMLReaderManager Maven / Gradle / Ivy
/*
* 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.
*/
/*
* $Id: XMLReaderManager.java 468655 2006-10-28 07:12:06Z minchau $
*/
package org.apache.xml.utils;
import java.util.Hashtable;
import javax.xml.parsers.FactoryConfigurationError;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;
import org.xml.sax.SAXException;
/**
* Creates XMLReader objects and caches them for re-use.
* This class follows the singleton pattern.
*/
public class XMLReaderManager {
private static final String NAMESPACES_FEATURE =
"http://xml.org/sax/features/namespaces";
private static final String NAMESPACE_PREFIXES_FEATURE =
"http://xml.org/sax/features/namespace-prefixes";
private static final XMLReaderManager m_singletonManager =
new XMLReaderManager();
/**
* Parser factory to be used to construct XMLReader objects
*/
private static SAXParserFactory m_parserFactory;
/**
* Cache of XMLReader objects
*/
private ThreadLocal m_readers;
/**
* Keeps track of whether an XMLReader object is in use.
*/
private Hashtable m_inUse;
/**
* Hidden constructor
*/
private XMLReaderManager() {
}
/**
* Retrieves the singleton reader manager
*/
public static XMLReaderManager getInstance() {
return m_singletonManager;
}
/**
* Retrieves a cached XMLReader for this thread, or creates a new
* XMLReader, if the existing reader is in use. When the caller no
* longer needs the reader, it must release it with a call to
* {@link #releaseXMLReader}.
*/
public synchronized XMLReader getXMLReader() throws SAXException {
XMLReader reader;
boolean readerInUse;
if (m_readers == null) {
// When the m_readers.get() method is called for the first time
// on a thread, a new XMLReader will automatically be created.
m_readers = new ThreadLocal();
}
if (m_inUse == null) {
m_inUse = new Hashtable();
}
// If the cached reader for this thread is in use, construct a new
// one; otherwise, return the cached reader.
reader = (XMLReader) m_readers.get();
boolean threadHasReader = (reader != null);
if (!threadHasReader || m_inUse.get(reader) == Boolean.TRUE) {
try {
try {
// According to JAXP 1.2 specification, if a SAXSource
// is created using a SAX InputSource the Transformer or
// TransformerFactory creates a reader via the
// XMLReaderFactory if setXMLReader is not used
reader = XMLReaderFactory.createXMLReader();
} catch (Exception e) {
try {
// If unable to create an instance, let's try to use
// the XMLReader from JAXP
if (m_parserFactory == null) {
m_parserFactory = SAXParserFactory.newInstance();
m_parserFactory.setNamespaceAware(true);
}
reader = m_parserFactory.newSAXParser().getXMLReader();
} catch (ParserConfigurationException pce) {
throw pce; // pass along pce
}
}
try {
reader.setFeature(NAMESPACES_FEATURE, true);
reader.setFeature(NAMESPACE_PREFIXES_FEATURE, false);
} catch (SAXException se) {
// Try to carry on if we've got a parser that
// doesn't know about namespace prefixes.
}
} catch (ParserConfigurationException ex) {
throw new SAXException(ex);
} catch (FactoryConfigurationError ex1) {
throw new SAXException(ex1.toString());
} catch (NoSuchMethodError ex2) {
} catch (AbstractMethodError ame) {
}
// Cache the XMLReader if this is the first time we've created
// a reader for this thread.
if (!threadHasReader) {
m_readers.set(reader);
m_inUse.put(reader, Boolean.TRUE);
}
} else {
m_inUse.put(reader, Boolean.TRUE);
}
return reader;
}
/**
* Mark the cached XMLReader as available. If the reader was not
* actually in the cache, do nothing.
*
* @param reader The XMLReader that's being released.
*/
public synchronized void releaseXMLReader(XMLReader reader) {
// If the reader that's being released is the cached reader
// for this thread, remove it from the m_isUse list.
if (m_readers.get() == reader && reader != null) {
m_inUse.remove(reader);
}
}
}