| /* |
| * 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); |
| } |
| } |
| } |