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/*
* $Id: XMLReaderManager.java,v 1.14 2010-11-01 04:34:52 joehw Exp $
*/
package com.sun.org.apache.xml.internal.utils;
import java.util.HashMap;
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();
private static final String property = "org.xml.sax.driver";
/**
* 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 HashMap 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;
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 HashMap();
}
// If the cached reader for this thread is in use, construct a new
// one; otherwise, return the cached reader unless it isn't an
// instance of the class set in the 'org.xml.sax.driver' property
reader = (XMLReader) m_readers.get();
boolean threadHasReader = (reader != null);
String factory = SecuritySupport.getInstance().getSystemProperty(property);
if (threadHasReader && m_inUse.get(reader) != Boolean.TRUE &&
( factory == null || reader.getClass().getName().equals(factory))) {
m_inUse.put(reader, Boolean.TRUE);
} else {
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);
}
}
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);
}
}
}