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jlechner |
/* LinkFilter.java --
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Copyright (C) 1999,2000,2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package gnu.xml.pipeline;
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import java.io.IOException;
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import java.net.URL;
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import java.util.Enumeration;
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import java.util.Vector;
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import org.xml.sax.Attributes;
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import org.xml.sax.SAXException;
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/**
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* Pipeline filter to remember XHTML links found in a document,
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* so they can later be crawled. Fragments are not counted, and duplicates
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* are ignored. Callers are responsible for filtering out URLs they aren't
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* interested in. Events are passed through unmodified.
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*
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* <p> Input MUST include a setDocumentLocator() call, as it's used to
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* resolve relative links in the absence of a "base" element. Input MUST
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* also include namespace identifiers, since it is the XHTML namespace
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* identifier which is used to identify the relevant elements.
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*
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* <p><em>FIXME:</em> handle xml:base attribute ... in association with
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* a stack of base URIs. Similarly, recognize/support XLink data.
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*
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* @author David Brownell
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*/
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public class LinkFilter extends EventFilter
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{
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// for storing URIs
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private Vector vector = new Vector ();
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// struct for "full" link record (tbd)
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// these for troubleshooting original source:
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// original uri
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// uri as resolved (base, relative, etc)
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// URI of originating doc
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// line #
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// original element + attrs (img src, desc, etc)
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// XLink model of the link ... for inter-site pairups ?
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private String baseURI;
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private boolean siteRestricted = false;
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//
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// XXX leverage blacklist info (like robots.txt)
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//
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// XXX constructor w/param ... pipeline for sending link data
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// probably XHTML --> XLink, providing info as sketched above
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//
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/**
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* Constructs a new event filter, which collects links in private data
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* structure for later enumeration.
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*/
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// constructor used by PipelineFactory
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public LinkFilter ()
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{
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super.setContentHandler (this);
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}
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/**
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* Constructs a new event filter, which collects links in private data
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* structure for later enumeration and passes all events, unmodified,
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* to the next consumer.
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*/
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// constructor used by PipelineFactory
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public LinkFilter (EventConsumer next)
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{
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super (next);
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super.setContentHandler (this);
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}
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/**
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* Returns an enumeration of the links found since the filter
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* was constructed, or since removeAllLinks() was called.
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*
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* @return enumeration of strings.
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*/
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public Enumeration getLinks ()
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{
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return vector.elements ();
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}
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/**
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* Removes records about all links reported to the event
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* stream, as if the filter were newly created.
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*/
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public void removeAllLinks ()
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{
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vector = new Vector ();
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}
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/**
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* Collects URIs for (X)HTML content from elements which hold them.
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*/
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public void startElement (
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String uri,
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String localName,
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String qName,
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Attributes atts
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) throws SAXException
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{
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String link;
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// Recognize XHTML links.
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if ("http://www.w3.org/1999/xhtml".equals (uri)) {
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if ("a".equals (localName) || "base".equals (localName)
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|| "area".equals (localName))
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link = atts.getValue ("href");
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else if ("iframe".equals (localName) || "frame".equals (localName))
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link = atts.getValue ("src");
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else if ("blockquote".equals (localName) || "q".equals (localName)
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|| "ins".equals (localName) || "del".equals (localName))
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link = atts.getValue ("cite");
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else
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link = null;
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link = maybeAddLink (link);
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// "base" modifies designated baseURI
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if ("base".equals (localName) && link != null)
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baseURI = link;
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if ("iframe".equals (localName) || "img".equals (localName))
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maybeAddLink (atts.getValue ("longdesc"));
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}
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super.startElement (uri, localName, qName, atts);
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}
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private String maybeAddLink (String link)
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{
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int index;
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// ignore empty links and fragments inside docs
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if (link == null)
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return null;
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if ((index = link.indexOf ("#")) >= 0)
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link = link.substring (0, index);
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if (link.equals (""))
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return null;
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try {
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// get the real URI
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URL base = new URL ((baseURI != null)
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? baseURI
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: getDocumentLocator ().getSystemId ());
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URL url = new URL (base, link);
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link = url.toString ();
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// ignore duplicates
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if (vector.contains (link))
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return link;
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// other than what "base" does, stick to original site:
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if (siteRestricted) {
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// don't switch protocols
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if (!base.getProtocol ().equals (url.getProtocol ()))
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return link;
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// don't switch servers
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if (base.getHost () != null
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&& !base.getHost ().equals (url.getHost ()))
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return link;
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}
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vector.addElement (link);
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return link;
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} catch (IOException e) {
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// bad URLs we don't want
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}
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return null;
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}
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/**
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* Reports an error if no Locator has been made available.
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*/
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public void startDocument ()
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throws SAXException
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{
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if (getDocumentLocator () == null)
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throw new SAXException ("no Locator!");
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}
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/**
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* Forgets about any base URI information that may be recorded.
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* Applications will often want to call removeAllLinks(), likely
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* after examining the links which were reported.
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*/
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public void endDocument ()
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throws SAXException
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{
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baseURI = null;
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super.endDocument ();
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}
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}
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