domparser.java

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/*
 * Copyright (C) 1999-2001 David Brownell
 * 
 * This file is part of GNU JAXP, a library.
 *
 * GNU JAXP is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 * 
 * GNU JAXP is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * As a special exception, if you link this library with other files to
 * produce an executable, this library does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * This exception does not however invalidate any other reasons why the
 * executable file might be covered by the GNU General Public License. 
 */

package gnu.xml.util;

import java.util.Enumeration;
import java.util.Locale;

import org.xml.sax.*;
import org.xml.sax.helpers.AttributesImpl;
import org.xml.sax.helpers.NamespaceSupport;
import org.xml.sax.ext.DeclHandler;
import org.xml.sax.ext.DefaultHandler2;
import org.xml.sax.ext.LexicalHandler;

import org.w3c.dom.*;


/**
 * This parser emits SAX2 parsing events as it traverses a DOM tree, using
 * any conformant implementation of DOM.  It exposes all SAX1 features,
 * and the following SAX2 features and properties (as
 * identified by standard URIs which are not fully provided here).  Note
 * that if a Level 1 DOM implementation is given, then this behaves as if
 * namespaces were disabled, and namespace prefixes were enabled.  </p>
 *
 * <table border="1" width='100%' cellpadding='3' cellspacing='0'>
 * <tr bgcolor='#ccccff'>
 *	<th><font size='+1'>Name</font></th>
 *	<th><font size='+1'>Notes</font></th></tr>
 *
 * <tr><td colspan=2><center><em>Features ... URL prefix is
 * <b>http://xml.org/sax/features/</b></em></center></td></tr>
 *
 * <tr><td>(URL)/external-general-entities</td>
 *	<td>false (does no parsing)</td></tr>
 * <tr><td>(URL)/external-parameter-entities</td>
 *	<td>false (does no parsing)</td></tr>
 * <tr><td>(URL)/namespaces</td>
 *	<td>Value is fixed at <em>true</em></td></tr>
 * <tr><td>(URL)/namespace-prefixes</td>
 *	<td>Value is settable, defaulting to <em>false</em>
 *	(<code>xmlns</code> attributes hidden, and names aren't prefixed)
 *	</td></tr>
 * <tr><td>(URL)/string-interning</td>
 *	<td>Value is fixed at <em>false</em> (DOM provides no
 *	guarantees as to interning)</td></tr>
 * <tr><td>(URL)/validation</td>
 *	<td>false (does no parsing)</td></tr>
 * <tr><td>(URL)/lexical-handler/parameter-entities</td>
 *	<td>false (DOM doesn't do parameter entities)</td></tr>
 *
 * <tr><td colspan=2><center><em>Properties ... URL prefix is
 * <b>http://xml.org/sax/properties/</b></em></center></td></tr>
 *
 *
 * <tr><td>(URL)/dom-node</td>
 *	<td>This property may be set before parsing to hold a DOM
 *	<em>Document</em> node; any arguments given to <em>parse</em>
 *	methods are ignored.  When retrieved
 *	during a parse, this value contains the "current" DOM node.
 *	</td></tr>
 * <tr><td>(URL)/declaration-handler</td>
 *	<td>A declaration handler may be provided.  Declaration of external
 *	general entities is exposed, but not parameter entities; none of the
 *	entity names reported here will begin with "%". </td></tr>
 * <tr><td>(URL)/lexical-handler</td>
 *	<td>A lexical handler may be provided.  While the start and end of
 *	any external subset are reported, expansion of other parameter
 *	entities (e.g. inside attribute list declarations) is not exposed.
 *	Expansion of general entities within attributes is also not exposed
 *	(see below).</td></tr>
 * </table>
 *
 * <P> The consequences of modifying a DOM document tree as it is being walked
 * by this "parser" are unspecified; don't do it! </P>
 *
 * @author David Brownell
 */
final public class DomParser implements XMLReader
{
    // Stuff used internally to route events correctly
    private DefaultHandler2	defaultHandler = new DefaultHandler2 ();

    // per-parse SAX stuff
    private ContentHandler	contentHandler = defaultHandler;
    private DTDHandler		dtdHandler = defaultHandler;
    private DeclHandler		declHandler = defaultHandler;
    private LexicalHandler	lexicalHandler = defaultHandler;

    // shared context
    private ErrorHandler	errHandler = defaultHandler;
    private EntityResolver	resolver = defaultHandler;
    private Locale		locale = Locale.getDefault ();

    // parser state
    private Node		start;
    private Node		current;
    private boolean		isL2;
    private boolean		showNamespaces = true;
    private boolean		showXML1_0 = false;
    private NamespaceSupport	prefixStack = new NamespaceSupport ();
    private boolean		isDocument;


    /**
     * Constructs an unitialized <b>SAX2</b> parser.
     */
    public DomParser () {
    } 

    /**
     * Constructs an <b>SAX2</b> parser initialized to traverse the specified
     * DOM tree.  If the node is a document, the startDocument() and
     * endDocument() calls bracket the calls exposing children.
     */
    public DomParser (Node node) {
	setStart (node);
    } 


    // stuff that most components in an application should be sharing:
    // resolver and error locale.

    /**
     * <b>SAX2</b>: Returns the object used when resolving external
     * entities during parsing (both general and parameter entities).
     */
    public EntityResolver getEntityResolver ()
    {
	return resolver;
    }

    /**
     * <b>SAX1</b>: Provides an object which may be used when resolving external
     * entities during parsing (both general and parameter entities).
     */
    public void setEntityResolver (EntityResolver resolver)
    {
	if (resolver == null)
	    resolver = defaultHandler;
	this.resolver = resolver;
    }

    /**
     * <b>SAX1</b>: Identifies the locale which the parser should use for the
     * diagnostics it provides.
     *
     * @exception SAXException as defined in the specification for
     *	<em>org.xml.sax.Parser.setLocale()</em>
     */
    public void setLocale (Locale locale)
    throws SAXException
    {
	if (locale == null)
	    locale = Locale.getDefault ();
	this.locale = locale;
    }

    
    // different modules will tend to handle error handling the same,
    // but it may not be the same through the whole app

    /**
     * <b>SAX2</b>: Returns the object used to receive callbacks for XML
     * errors of all levels (fatal, nonfatal, warning).
     */
    public ErrorHandler getErrorHandler ()
    {
	return errHandler;
    }

    /**
     * <b>SAX1</b>: Provides an object which receives callbacks for XML errors
     * of all levels (fatal, nonfatal, warning).
     */
    public void setErrorHandler (ErrorHandler handler)
    {
	if (handler == null)
	    handler = defaultHandler;
	errHandler = handler;
    }


    // stuff different parts of a module will handle differently

    /**
     * <b>SAX2</b>: Returns the object used to report the logical
     * content of an XML document.
     */
    public ContentHandler getContentHandler ()
    {
	return contentHandler;
    }

    /**
     * <b>SAX2</b>: Assigns the object used to report the logical
     * content of an XML document.
     */
    public void setContentHandler (ContentHandler handler)
    {
	if (handler == null)
	    handler = defaultHandler;
	contentHandler = handler;
    }

    /**
     * <b>SAX2</b>: Returns the object used to process declarations related
     * to notations and unparsed entities.
     */
    public DTDHandler getDTDHandler ()
    {
	return dtdHandler;
    }

    /**
     * <b>SAX1</b>: Provides an object which may be used to intercept
     * declarations related to notations and unparsed entities.
     */
    public void setDTDHandler (DTDHandler handler)
    {
	if (handler == null)
	    handler = defaultHandler;
	dtdHandler = handler;
    }


    /**
     * <b>SAX1</b>:  Parses the previously provided DOM document (the
     * input parameter is ignored).  When this returns, that same
     * document may be parsed again without needing a "reset".
     *
     * @param uri ignored (pass an empty string)
     * @exception SAXException as defined in the specification for
     *	<em>org.xml.sax.Parser.parse()</em>
     */
    public void parse (String uri) throws SAXException
    {
	parse ();
    }

    /**
     * <b>SAX1</b>:  Parses the previously provided DOM document (the
     * input parameter is ignored).  When this returns, that same
     * document may be parsed again without needing a "reset".
     *
     * @param input ignored
     * @exception SAXException as defined in the specification for
     *	<em>org.xml.sax.Parser.parse()</em>
     */
    public void parse (InputSource input) throws SAXException
    {
	parse ();
    }

    private void parse () throws SAXException
    {
	try {
	    walk ();
	} finally {
	    if (isDocument)
		contentHandler.endDocument ();
	    current = null;
	    prefixStack.reset ();
	}
    }

    private boolean getIsL2 (Node node)
    {
	DOMImplementation	impl;
	Document		doc;

	if (node instanceof Document)
	    doc = (Document) node;
	else
	    doc = node.getOwnerDocument ();
	if (doc == null)
	    throw new RuntimeException ("? unowned node - L2 DTD ?");
	impl = doc.getImplementation ();
	return impl.hasFeature ("XML", "2.0");
    }


    private static final String FEATURES = "http://xml.org/sax/features/";
    private static final String HANDLERS = "http://xml.org/sax/properties/";

    /**
     * <b>SAX2</b>: Tells whether this parser supports the specified feature.
     */
    public boolean getFeature (String name)
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	// basically, none are relevant -- they relate more to
	// parsing than to walking a "parse tree".

		// FIXME: DOM feature to expose interning?

	if ((FEATURES + "validation").equals (name)
		|| (FEATURES + "external-general-entities")
		    .equals (name)
		|| (FEATURES + "external-parameter-entities")
		    .equals (name)
		|| (FEATURES + "string-interning").equals (name)
		)
	    return false;
    
	if ((FEATURES + "namespaces").equals (name))
	    return showNamespaces;
	if ((FEATURES + "namespace-prefixes").equals (name))
	    return showXML1_0;

	throw new SAXNotRecognizedException (name);
    }

    /**
     * <b>SAX2</b>:  Returns the specified property.  At this time only
     * the declaration and lexical handlers, and current the "DOM" node,
     * are supported.
     */
    public Object getProperty (String name)
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if ((HANDLERS + "declaration-handler").equals (name))
	    return declHandler == defaultHandler ? null : declHandler;
	if ((HANDLERS + "lexical-handler").equals (name))
	    return lexicalHandler == defaultHandler ? null : lexicalHandler;

	if ((HANDLERS + "dom-node").equals (name))
	    return current;

	// unknown properties
	throw new SAXNotRecognizedException (name);
    }

    /**
     * <b>SAX2</b>:  Sets the state of features supported in this parser.
     * Only the namespace support features are mutable.
     */
    public void setFeature (String name, boolean state)
    throws SAXNotRecognizedException, SAXNotSupportedException
    {
	if (current != null)
	    throw new IllegalStateException ("feature change midparse");

	boolean value = getFeature (name);

	if (value == state)
	    return;

	if ((FEATURES + "namespaces").equals (name)) {
	    if (!showXML1_0 && state == false)
		throw new SAXNotSupportedException ("Illegal namespace "
			+ "processing configuration");
	    showNamespaces = state;
	    return;
	}
	if ((FEATURES + "namespace-prefixes").equals (name)) {
	    if (!showNamespaces && state == false)
		throw new SAXNotSupportedException ("Illegal namespace "
			+ "processing configuration");
	    showXML1_0 = state;
	    return;
	}

	throw new SAXNotSupportedException (name);
    }

    /**
     * <b>SAX2</b>:  Assigns the specified property.  At this time only
     * declaration and lexical handlers, and the initial DOM document, are
     * supported.  These must not be changed to values of the wrong type.
     * Like SAX1 handlers, these handlers may be changed at any time.
     * Like SAX1 input source or document URI, the initial DOM document
     * may not be changed during a parse.