/*
* @(#)$Id: DocumentCache.java,v 1.2 2001/05/01 13:16:21 morten Exp $
*
* The Apache Software License, Version 1.1
*
*
* Copyright (c) 2001 The Apache Software Foundation. All rights
* reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 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 end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Xalan" and "Apache Software Foundation" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact apache@apache.org.
*
* 5. Products derived from this software may not be called "Apache",
* nor may "Apache" appear in their name, without prior written
* permission of the Apache Software Foundation.
*
* THIS SOFTWARE IS PROVIDED ``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 THE APACHE SOFTWARE FOUNDATION 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.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation and was
* originally based on software copyright (c) 2001, Sun
* Microsystems., http://www.sun.com. For more
* information on the Apache Software Foundation, please see
* <http://www.apache.org/>.
*
* @author Morten Jorgensen
*
*/
package org.apache.xalan.xsltc.dom;
import java.io.PrintWriter;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.net.MalformedURLException;
import java.util.Hashtable;
import java.util.Date;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.XMLReader;
import org.xml.sax.SAXException;
import org.apache.xalan.xsltc.DOM;
import org.apache.xalan.xsltc.DOMCache;
import org.apache.xalan.xsltc.Translet;
import org.apache.xalan.xsltc.dom.DOMImpl;
import org.apache.xalan.xsltc.dom.DTDMonitor;
import org.apache.xalan.xsltc.runtime.AbstractTranslet;
public final class DocumentCache implements DOMCache {
private int _size;
private Hashtable _references;
private String[] _URIs;
private int _count;
private int _current;
private SAXParser _parser;
private XMLReader _reader;
/*
* Inner class containing a DOMImpl object and DTD handler
*/
public final class CachedDocument {
// Statistics data
private long _firstReferenced;
private long _lastReferenced;
private long _accessCount;
private long _lastModified;
private long _lastChecked;
private long _buildTime;
// DOM and DTD handler references
private DOMImpl _dom = null;
private DTDMonitor _dtdMonitor = null;
/**
* Constructor - load document and initialise statistics
*/
public CachedDocument(String uri) {
// Initialise statistics variables
final long stamp = System.currentTimeMillis();
_firstReferenced = stamp;
_lastReferenced = stamp;
_accessCount = 0;
loadDocument(uri);
_buildTime = System.currentTimeMillis() - stamp;
}
/**
* Loads the document and updates build-time (latency) statistics
*/
public void loadDocument(String uri) {
_dom = new DOMImpl();
_dtdMonitor = new DTDMonitor();
try {
final long stamp = System.currentTimeMillis();
_reader.setContentHandler(_dom.getBuilder());
_dtdMonitor.handleDTD(_reader);
_reader.parse(uri);
_dom.setDocumentURI(uri);
// The build time can be used for statistics for a better
// priority algorithm (currently round robin).
final long thisTime = System.currentTimeMillis() - stamp;
if (_buildTime > 0)
_buildTime = (_buildTime + thisTime) >>> 1;
else
_buildTime = thisTime;
}
catch (Exception e) {
_dom = null;
_dtdMonitor = null;
}
}
public DOMImpl getDocument() { return(_dom); }
public DTDMonitor getDTDMonitor() { return(_dtdMonitor); }
public long getFirstReferenced() { return(_firstReferenced); }
public long getLastReferenced() { return(_lastReferenced); }
public long getAccessCount() { return(_accessCount); }
public void incAccessCount() { _accessCount++; }
public long getLastModified() { return(_lastModified); }
public void setLastModified(long t){ _lastModified = t; }
public long getLatency() { return(_buildTime); }
public long getLastChecked() { return(_lastChecked); }
public void setLastChecked(long t) { _lastChecked = t; }
public long getEstimatedSize() {
if (_dom != null)
return(_dom.getSize() << 5); // ???
else
return(0);
}
}
/**
* DocumentCache constructor
*/
public DocumentCache(int size) throws SAXException {
_count = 0;
_current = 0;
_size = size;
_references = new Hashtable(_size+2);
_URIs = new String[_size];
try {
// Create a SAX parser and get the XMLReader object it uses
final SAXParserFactory factory = SAXParserFactory.newInstance();
_parser = factory.newSAXParser();
_reader = _parser.getXMLReader();
}
catch (ParserConfigurationException e) {
System.err.println("Your SAX parser is not configured correctly.");
System.exit(-1);
}
}
/**
* Returns the time-stamp for a document's last update
*/
private final long getLastModified(String uri) {
try {
URL url = new URL(uri);
URLConnection connection = url.openConnection();
long timestamp = connection.getLastModified();
return(timestamp);
}
catch (MalformedURLException e) {
return(System.currentTimeMillis());
}
catch (IOException e) {
return(System.currentTimeMillis());
}
}
/**
*
*/
private CachedDocument lookupDocument(String uri) {
return((CachedDocument)_references.get(uri));
}
/**
*
*/
private synchronized void insertDocument(String uri, CachedDocument doc) {
if (_count < _size) {
// Insert out URI in circular buffer
_URIs[_count++] = uri;
_current = 0;
}
else {
// Remove oldest URI from reference Hashtable
_references.remove(_URIs[_current]);
// Insert our URI in circular buffer
_URIs[_current] = uri;
if (++_current >= _size) _current = 0;
}
_references.put(uri, doc);
}
/**
*
*/
private synchronized void replaceDocument(String uri, CachedDocument doc) {
CachedDocument old = (CachedDocument)_references.get(uri);
if (doc == null)
insertDocument(uri, doc);
else
_references.put(uri, doc);
}
/**
* Returns a document either by finding it in the cache or
* downloading it and putting it in the cache.
*/
public final DOMImpl retrieveDocument(String uri, int mask, Translet trs) {
CachedDocument doc;
// Try to get the document from the cache first
if ((doc = lookupDocument(uri)) == null) {
doc = new CachedDocument(uri);
if (doc == null) return null; // better error handling needed!!!
doc.setLastModified(getLastModified(uri));
insertDocument(uri, doc);
}
// If the document is in the cache we must check if it is still valid
else {
long now = System.currentTimeMillis();
long chk = doc.getLastChecked();
doc.setLastChecked(now);
// Has the modification time for this file been checked lately?
if (now > (chk + 600000)) {
doc.setLastChecked(now);
long last = getLastModified(uri);
// Reload document if it has been modified since last download
if (last > doc.getLastModified()) {
doc = new CachedDocument(uri);
if (doc == null) return null;
doc.setLastModified(getLastModified(uri));
replaceDocument(uri, doc);
}
}
}
// Get the references to the actual DOM and DTD handler
final DOMImpl dom = doc.getDocument();
final DTDMonitor dtd = doc.getDTDMonitor();
// The dom reference may be null if the URL pointed to a
// non-existing document
if (dom == null) return null;
doc.incAccessCount(); // For statistics
final AbstractTranslet translet = (AbstractTranslet)trs;
// Set minimum needed size for key/id indices in the translet
translet.setIndexSize(dom.getSize());
// Create index for any ID attributes defined in the document DTD
dtd.buildIdIndex(dom, mask, translet);
// Pass all unparsed entities to the translet
translet.setUnparsedEntityURIs(dtd.getUnparsedEntityURIs());
return(doc.getDocument());
}
/**
* Outputs the cache statistics
*/
public void getStatistics(PrintWriter out) {
out.println("<h2>DOM cache statistics</h2><center><table border=\"2\">"+
"<tr><td><b>Document URI</b></td>"+
"<td><center><b>Build time</b></center></td>"+
"<td><center><b>Access count</b></center></td>"+
"<td><center><b>Last accessed</b></center></td>"+
"<td><center><b>Last modified</b></center></td></tr>");
for (int i=0; i<_count; i++) {
CachedDocument doc = (CachedDocument)_references.get(_URIs[i]);
out.print("<tr><td><a href=\""+_URIs[i]+"\">"+
"<font size=-1>"+_URIs[i]+"</font></a></td>");
out.print("<td><center>"+doc.getLatency()+"ms</center></td>");
out.print("<td><center>"+doc.getAccessCount()+"</center></td>");
out.print("<td><center>"+(new Date(doc.getLastReferenced()))+
"</center></td>");
out.print("<td><center>"+(new Date(doc.getLastModified()))+
"</center></td>");
out.println("</tr>");
}
out.println("</table></center>");
}
}