/*
* Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
*
* This software is open source.
* See the bottom of this file for the licence.
*/
package org.orbeon.dom4j.tree;
import org.orbeon.dom4j.Namespace;
import java.lang.ref.WeakReference;
import java.lang.reflect.Constructor;
import java.util.Map;
/**
* <p>
* <code>NamespaceCache</code> caches instances of
* <code>DefaultNamespace</code> for reuse both across documents and within
* documents.
* </p>
*
* @author <a href="mailto:james.strachan@metastuff.com">James Strachan </a>
* @author Maarten Coene
* @author Brett Finnell
* @version $Revision: 1.15 $
*/
public class NamespaceCache {
private static final String CONCURRENTREADERHASHMAP_CLASS
= "EDU.oswego.cs.dl.util.concurrent.ConcurrentReaderHashMap";
/**
* Cache of {@link Map}instances indexed by URI which contain caches of
* {@link Namespace}for each prefix
*/
protected static Map cache;
/**
* Cache of {@link Namespace}instances indexed by URI for default
* namespaces with no prefixes
*/
protected static Map noPrefixCache;
static {
/* Try the java.util.concurrent.ConcurrentHashMap first. */
try {
Class clazz = Class
.forName("java.util.concurrent.ConcurrentHashMap");
Constructor construct = clazz.getConstructor(new Class[] {
Integer.TYPE, Float.TYPE, Integer.TYPE });
cache = (Map) construct.newInstance(new Object[] {new Integer(11),
new Float(0.75f), new Integer(1) });
noPrefixCache = (Map) construct.newInstance(new Object[] {
new Integer(11), new Float(0.75f), new Integer(1) });
} catch (Throwable t1) {
/* Try to use the util.concurrent library (if in classpath) */
try {
Class clazz = Class.forName(CONCURRENTREADERHASHMAP_CLASS);
cache = (Map) clazz.newInstance();
noPrefixCache = (Map) clazz.newInstance();
} catch (Throwable t2) {
/* If previous implementations fail, use internal one */
cache = new ConcurrentReaderHashMap();
noPrefixCache = new ConcurrentReaderHashMap();
}
}
}
/**
* DOCUMENT ME!
*
* @param prefix
* DOCUMENT ME!
* @param uri
* DOCUMENT ME!
*
* @return the namespace for the given prefix and uri
*/
public Namespace get(String prefix, String uri) {
Map uriCache = getURICache(uri);
WeakReference ref = (WeakReference) uriCache.get(prefix);
Namespace answer = null;
if (ref != null) {
answer = (Namespace) ref.get();
}
if (answer == null) {
synchronized (uriCache) {
ref = (WeakReference) uriCache.get(prefix);
if (ref != null) {
answer = (Namespace) ref.get();
}
if (answer == null) {
answer = createNamespace(prefix, uri);
uriCache.put(prefix, new WeakReference(answer));
}
}
}
return answer;
}
/**
* DOCUMENT ME!
*
* @param uri
* DOCUMENT ME!
*
* @return the name model for the given name and namepsace
*/
public Namespace get(String uri) {
WeakReference ref = (WeakReference) noPrefixCache.get(uri);
Namespace answer = null;
if (ref != null) {
answer = (Namespace) ref.get();
}
if (answer == null) {
synchronized (noPrefixCache) {
ref = (WeakReference) noPrefixCache.get(uri);
if (ref != null) {
answer = (Namespace) ref.get();
}
if (answer == null) {
answer = createNamespace("", uri);
noPrefixCache.put(uri, new WeakReference(answer));
}
}
}
return answer;
}
/**
* DOCUMENT ME!
*
* @param uri
* DOCUMENT ME!
*
* @return the cache for the given namespace URI. If one does not currently
* exist it is created.
*/
protected Map getURICache(String uri) {
Map answer = (Map) cache.get(uri);
if (answer == null) {
synchronized (cache) {
answer = (Map) cache.get(uri);
if (answer == null) {
answer = new ConcurrentReaderHashMap();
cache.put(uri, answer);
}
}
}
return answer;
}
/**
* A factory method to create {@link Namespace}instance
*
* @param prefix
* DOCUMENT ME!
* @param uri
* DOCUMENT ME!
*
* @return a newly created {@link Namespace}instance.
*/
protected Namespace createNamespace(String prefix, String uri) {
return new Namespace(prefix, uri);
}
}
/*
* Redistribution and use of this software and associated documentation
* ("Software"), with or without modification, are permitted provided that the
* following conditions are met:
*
* 1. Redistributions of source code must retain copyright statements and
* notices. Redistributions must also contain a copy of this document.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The name "DOM4J" must not be used to endorse or promote products derived
* from this Software without prior written permission of MetaStuff, Ltd. For
* written permission, please contact dom4j-info@metastuff.com.
*
* 4. Products derived from this Software may not be called "DOM4J" nor may
* "DOM4J" appear in their names without prior written permission of MetaStuff,
* Ltd. DOM4J is a registered trademark of MetaStuff, Ltd.
*
* 5. Due credit should be given to the DOM4J Project - http://www.dom4j.org
*
* THIS SOFTWARE IS PROVIDED BY METASTUFF, LTD. AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL METASTUFF, LTD. OR ITS CONTRIBUTORS BE
* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
* Copyright 2001-2005 (C) MetaStuff, Ltd. All Rights Reserved.
*/