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jlechner |
/* NSFilter.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.util.Enumeration;
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import java.util.Stack;
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import org.xml.sax.Attributes;
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import org.xml.sax.ErrorHandler;
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import org.xml.sax.Locator;
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import org.xml.sax.SAXException;
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import org.xml.sax.SAXParseException;
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import org.xml.sax.helpers.AttributesImpl;
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import org.xml.sax.helpers.NamespaceSupport;
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/**
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* This filter ensures that element and attribute names are properly prefixed,
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* and that such prefixes are declared. Such data is critical for operations
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* like writing XML text, and validating against DTDs: names or their prefixes
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* may have been discarded, although they are essential to the exchange of
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* information using XML. There are various common ways that such data
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* gets discarded: <ul>
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*
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* <li> By default, SAX2 parsers must discard the "xmlns*"
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* attributes, and may also choose not to report properly prefixed
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* names for elements or attributes. (Some parsers may support
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* changing the <em>namespace-prefixes</em> value from the default
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* to <em>true</em>, effectively eliminating the need to use this
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* filter on their output.)
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*
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* <li> When event streams are generated from a DOM tree, they may
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* have never have had prefixes or declarations for namespaces; or
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* the existing prefixes or declarations may have been invalidated
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* by structural modifications to that DOM tree.
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*
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* <li> Other software writing SAX event streams won't necessarily
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* be worrying about prefix management, and so they will need to
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* have a transparent solution for managing them.
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*
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* </ul>
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*
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* <p> This filter uses a heuristic to choose the prefix to assign to any
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* particular name which wasn't already corectly prefixed. The associated
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* namespace will be correct, and the prefix will be declared. Original
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* structures facilitating text editing, such as conventions about use of
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* mnemonic prefix names or the scoping of prefixes, can't always be
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* reconstructed after they are discarded, as strongly encouraged by the
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* current SAX2 defaults.
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*
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* <p> Note that this can't possibly know whether values inside attribute
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* value or document content involve prefixed names. If your application
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* requires using prefixed names in such locations you'll need to add some
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* appropriate logic (perhaps adding additional heuristics in a subclass).
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*
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* @author David Brownell
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*/
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public class NSFilter extends EventFilter
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{
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private NamespaceSupport nsStack = new NamespaceSupport ();
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private Stack elementStack = new Stack ();
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private boolean pushedContext;
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private String nsTemp [] = new String [3];
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private AttributesImpl attributes = new AttributesImpl ();
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private boolean usedDefault;
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// gensymmed prefixes use this root name
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private static final String prefixRoot = "prefix-";
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/**
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* Passes events through to the specified consumer, after first
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* processing them.
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*
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* @param next the next event consumer to receive events.
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*/
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// constructor used by PipelineFactory
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public NSFilter (EventConsumer next)
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{
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super (next);
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setContentHandler (this);
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}
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private void fatalError (String message)
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throws SAXException
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{
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SAXParseException e;
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ErrorHandler handler = getErrorHandler ();
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Locator locator = getDocumentLocator ();
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if (locator == null)
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e = new SAXParseException (message, null, null, -1, -1);
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else
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e = new SAXParseException (message, locator);
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if (handler != null)
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handler.fatalError (e);
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throw e;
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}
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public void startDocument () throws SAXException
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{
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elementStack.removeAllElements ();
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nsStack.reset ();
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pushedContext = false;
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super.startDocument ();
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}
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/**
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* This call is not passed to the next consumer in the chain.
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* Prefix declarations and scopes are only exposed in the form
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* of attributes; this callback just records a declaration that
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* will be exposed as an attribute.
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*/
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public void startPrefixMapping (String prefix, String uri)
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throws SAXException
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{
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if (pushedContext == false) {
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nsStack.pushContext ();
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pushedContext = true;
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}
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// this check is awkward, but the paranoia prevents big trouble
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for (Enumeration e = nsStack.getDeclaredPrefixes ();
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e.hasMoreElements ();
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/* NOP */ ) {
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String declared = (String) e.nextElement ();
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if (!declared.equals (prefix))
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continue;
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if (uri.equals (nsStack.getURI (prefix)))
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return;
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fatalError ("inconsistent binding for prefix '" + prefix
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+ "' ... " + uri + " (was " + nsStack.getURI (prefix) + ")");
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}
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if (!nsStack.declarePrefix (prefix, uri))
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fatalError ("illegal prefix declared: " + prefix);
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}
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private String fixName (String ns, String l, String name, boolean isAttr)
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throws SAXException
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{
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if ("".equals (name) || name == null) {
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name = l;
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if ("".equals (name) || name == null)
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fatalError ("empty/null name");
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}
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// can we correctly process the name as-is?
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// handles "element scope" attribute names here.
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if (nsStack.processName (name, nsTemp, isAttr) != null
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&& nsTemp [0].equals (ns)
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) {
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return nsTemp [2];
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}
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// nope, gotta modify the name or declare a default mapping
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int temp;
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// get rid of any current prefix
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if ((temp = name.indexOf (':')) >= 0) {
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name = name.substring (temp + 1);
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// ... maybe that's enough (use/prefer default namespace) ...
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if (!isAttr && nsStack.processName (name, nsTemp, false) != null
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&& nsTemp [0].equals (ns)
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) {
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return nsTemp [2];
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}
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}
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// must we define and use the default/undefined prefix?
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if ("".equals (ns)) {
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if (isAttr)
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fatalError ("processName bug");
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if (attributes.getIndex ("xmlns") != -1)
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fatalError ("need to undefine default NS, but it's bound: "
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+ attributes.getValue ("xmlns"));
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nsStack.declarePrefix ("", "");
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attributes.addAttribute ("", "", "xmlns", "CDATA", "");
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return name;
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}
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// is there at least one non-null prefix we can use?
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for (Enumeration e = nsStack.getDeclaredPrefixes ();
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e.hasMoreElements ();
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/* NOP */) {
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String prefix = (String) e.nextElement ();
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String uri = nsStack.getURI (prefix);
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if (uri == null || !uri.equals (ns))
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continue;
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return prefix + ":" + name;
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}
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// no such luck. create a prefix name, declare it, use it.
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for (temp = 0; temp >= 0; temp++) {
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String prefix = prefixRoot + temp;
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if (nsStack.getURI (prefix) == null) {
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nsStack.declarePrefix (prefix, ns);
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attributes.addAttribute ("", "", "xmlns:" + prefix,
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"CDATA", ns);
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return prefix + ":" + name;
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}
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}
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fatalError ("too many prefixes genned");
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// NOTREACHED
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return null;
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}
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public void startElement (
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String uri, String localName,
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String qName, Attributes atts
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) throws SAXException
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{
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if (!pushedContext)
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nsStack.pushContext ();
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pushedContext = false;
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// make sure we have all NS declarations handy before we start
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int length = atts.getLength ();
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for (int i = 0; i < length; i++) {
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String aName = atts.getQName (i);
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if (!aName.startsWith ("xmlns"))
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continue;
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String prefix;
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if ("xmlns".equals (aName))
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prefix = "";
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else if (aName.indexOf (':') == 5)
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prefix = aName.substring (6);
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else // "xmlnsfoo" etc.
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continue;
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startPrefixMapping (prefix, atts.getValue (i));
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}
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// put namespace decls at the start of our regenned attlist
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attributes.clear ();
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for (Enumeration e = nsStack.getDeclaredPrefixes ();
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e.hasMoreElements ();
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/* NOP */) {
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String prefix = (String) e.nextElement ();
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attributes.addAttribute ("", "",
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("".equals (prefix)
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? "xmlns"
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: "xmlns:" + prefix),
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"CDATA",
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nsStack.getURI (prefix));
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}
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// name fixups: element, then attributes.
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// fixName may declare a new prefix or, for the element,
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// redeclare the default (if element name needs it).
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qName = fixName (uri, localName, qName, false);
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for (int i = 0; i < length; i++) {
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String aName = atts.getQName (i);
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String aNS = atts.getURI (i);
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String aLocal = atts.getLocalName (i);
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String aType = atts.getType (i);
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String aValue = atts.getValue (i);
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if (aName.startsWith ("xmlns"))
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continue;
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aName = fixName (aNS, aLocal, aName, true);
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attributes.addAttribute (aNS, aLocal, aName, aType, aValue);
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}
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elementStack.push (qName);
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// pass event along, with cleaned-up names and decls.
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super.startElement (uri, localName, qName, attributes);
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}
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public void endElement (String uri, String localName, String qName)
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throws SAXException
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{
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nsStack.popContext ();
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qName = (String) elementStack.pop ();
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super.endElement (uri, localName, qName);
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}
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/**
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* This call is not passed to the next consumer in the chain.
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* Prefix declarations and scopes are only exposed in their
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* attribute form.
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*/
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public void endPrefixMapping (String prefix)
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throws SAXException
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{ }
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public void endDocument () throws SAXException
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{
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elementStack.removeAllElements ();
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nsStack.reset ();
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super.endDocument ();
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}
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}
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