xcat.java

linux下建立JAVA虚拟机的源码KAFFE

/* XCat.java -- 
   Copyright (C) 2001 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath 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, or (at your option)
any later version.

GNU Classpath 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 GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package gnu.xml.util;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.net.URL;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.StringTokenizer;
import java.util.Stack;
import java.util.Vector;

import org.xml.sax.Attributes;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;

import org.xml.sax.ext.DefaultHandler2;
import org.xml.sax.ext.EntityResolver2;

import org.xml.sax.helpers.XMLReaderFactory;

/**
 * Packages <a href=
    "http://www.oasis-open.org/committees/entity/spec-2001-08-06.html"
    >OASIS XML Catalogs</a>,
 * primarily for entity resolution by parsers.
 * That specification defines an XML syntax for mappings between
 * identifiers declared in DTDs (particularly PUBLIC identifiers) and
 * locations.  SAX has always supported such mappings, but conventions for
 * an XML file syntax to maintain them have previously been lacking.
 *
 * <p> This has three main operational modes.  The primary intended mode is
 * to create a resolver, then preloading it with one or more site-standard
 * catalogs before using it with one or more SAX parsers: <pre>
 *	XCat	catalog = new XCat ();
 *	catalog.setErrorHandler (diagnosticErrorHandler);
 *	catalog.loadCatalog ("file:/local/catalogs/catalog.cat");
 *	catalog.loadCatalog ("http://shared/catalog.cat");
 *	...
 *	catalog.disableLoading ();
 *	parser1.setEntityResolver (catalog);
 *	parser2.setEntityResolver (catalog);
 *	...</pre>
 *
 * <p>A second mode is to arrange that your application uses instances of
 * this class as its entity resolver, and automatically loads catalogs
 * referenced by <em>&lt;?oasis-xml-catalog...?&gt;</em> processing
 * instructions found before the DTD in documents it parses.
 * It would then discard the resolver after each parse.
 *
 * <p> A third mode applies catalogs in contexts other than entity
 * resolution for parsers.
 * The {@link #resolveURI resolveURI()} method supports resolving URIs
 * stored in XML application data, rather than inside DTDs.
 * Catalogs would be loaded as shown above, and the catalog could
 * be used concurrently for parser entity resolution and for
 * application URI resolution.
 * </p>
 *
 * <center><hr width='70%'></center>
 *
 * <p>Errors in catalogs implicitly loaded (during resolution) are ignored
 * beyond being reported through any <em>ErrorHandler</em> assigned using
 * {@link #setErrorHandler setErrorHandler()}.  SAX exceptions
 * thrown from such a handler won't abort resolution, although throwing a
 * <em>RuntimeException</em> or <em>Error</em> will normally abort both
 * resolution and parsing.  Useful diagnostic information is available to
 * any <em>ErrorHandler</em> used to report problems, or from any exception
 * thrown from an explicit {@link #loadCatalog loadCatalog()} invocation.
 * Applications can use that information as troubleshooting aids.
 *
 * <p>While this class requires <em>SAX2 Extensions 1.1</em> classes in
 * its class path, basic functionality does not require using a SAX2
 * parser that supports the extended entity resolution functionality.
 * See the original SAX1
 * {@link #resolveEntity(java.lang.String,java.lang.String) resolveEntity()}
 * method for a list of restrictions which apply when it is used with
 * older SAX parsers.
 *
 * @see EntityResolver2
 *
 * @author David Brownell
 */
public class XCat implements EntityResolver2
{
    private Catalog		catalogs [];
    private boolean		usingPublic = true;
    private boolean		loadingPermitted = true;
    private boolean		unified = true;
    private String		parserClass;
    private ErrorHandler	errorHandler;

    // private EntityResolver	next;	// chain to next if we fail...

    //
    // NOTE:  This is a straightforward implementation, and if
    // there are lots of "nextCatalog" or "delegate*" entries
    // in use, two tweaks would be worth considering:
    //
    //	- Centralize some sort of cache (key by URI) for individual
    //	  resolvers.  That'd avoid multiple copies of a given catalog.
    //
    //	- Have resolution track what catalogs (+modes) have been
    //	  searched.  This would support loop detection.
    //


    /**
     * Initializes without preloading a catalog.
     * This API is convenient when you may want to arrange that catalogs
     * are automatically loaded when explicitly referenced in documents,
     * using the <em>oasis-xml-catalog</em> processing instruction.
     * In such cases you won't usually be able to preload catalogs.
     */
    public XCat () { }

    /**
     * Initializes, and preloads a catalog using the default SAX parser.
     * This API is convenient when you operate with one or more standard
     * catalogs.
     *
     * <p> This just delegates to {@link #loadCatalog loadCatalog()};
     * see it for exception information.
     *
     * @param uri absolute URI for the catalog file.
     */
    public XCat (String uri)
    throws SAXException, IOException
	{ loadCatalog (uri); }


    /**
     * Loads an OASIS XML Catalog.
     * It is appended to the list of currently active catalogs, or
     * reloaded if a catalog with the same URI was already loaded.
     * Callers have control over what parser is used, how catalog parsing
     * errors are reported, and whether URIs will be resolved consistently.
     *
     * <p> The OASIS specification says that errors detected when loading
     * catalogs "must recover by ignoring the catalog entry file that
     * failed, and proceeding."  In this API, that action can be the
     * responsibility of applications, when they explicitly load any
     * catalog using this method.
     *
     * <p>Note that catalogs referenced by this one will not be loaded
     * at this time.  Catalogs referenced through <em>nextCatalog</em>
     * or <em>delegate*</em> elements are normally loaded only if needed. 
     *
     * @see #setErrorHandler
     * @see #setParserClass
     * @see #setUnified
     *
     * @param uri absolute URI for the catalog file.
     *
     * @exception IOException As thrown by the parser, typically to
     *	indicate problems reading data from that URI.
     * @exception SAXException As thrown by the parser, typically to
     *	indicate problems parsing data from that URI.  It may also
     *  be thrown if the parser doesn't support necessary handlers. 
     * @exception IllegalStateException When attempting to load a
     *	catalog after loading has been {@link #disableLoading disabled},
     *	such as after any entity or URI lookup has been performed.
     */
    public synchronized void loadCatalog (String uri)
    throws SAXException, IOException
    {
	Catalog		catalog;
	int		index = -1;

	if (!loadingPermitted)
	    throw new IllegalStateException ();
	
	uri = normalizeURI (uri);
	if (catalogs != null) {
	    // maybe just reload
	    for (index = 0; index < catalogs.length; index++)
		if (uri.equals (catalogs [index].catalogURI))
		    break;
	}
	catalog = loadCatalog (parserClass, errorHandler, uri, unified);

	// add to list of catalogs
	if (catalogs == null) {
	    index = 0;
	    catalogs = new Catalog [1];
	} else if (index == catalogs.length) {
	    Catalog		tmp [];

	    tmp = new Catalog [index + 1];
	    System.arraycopy (catalogs, 0, tmp, 0, index);
	    catalogs = tmp;
	}
	catalogs [index] = catalog;
    }


    /**
     * "New Style" external entity resolution for parsers.
     * Calls to this method prevent explicit loading of additional catalogs
     * using {@link #loadCatalog loadCatalog()}.
     *
     * <p>This supports the full core catalog functionality for locating
     * (and relocating) parsed entities that have been declared in a
     * document's DTD.
     *
     * @param name Entity name, such as "dudley", "%nell", or "[dtd]".
     * @param publicId Either a normalized public ID, or null.
     * @param baseURI Absolute base URI associated with systemId.
     * @param systemId URI found in entity declaration (may be
     *	relative to baseURI).
     *
     * @return Input source for accessing the external entity, or null
     *	if no mapping was found.  The input source may have opened
     *	the stream, and will have a fully resolved URI.
     *
     * @see #getExternalSubset
     */
    public InputSource resolveEntity (
	String name,		// UNUSED ... systemId is always non-null
	String publicId,
	String baseURI,		// UNUSED ... it just lets sysId be relative
	String systemId
    ) throws SAXException, IOException
    {
	if (loadingPermitted)
	    disableLoading ();

	try {
	    // steps as found in OASIS XML catalog spec 7.1.2
	    // steps 1, 8 involve looping over the list of catalogs
	    for (int i = 0; i < catalogs.length; i++) {
		InputSource	retval;
		retval = catalogs [i].resolve (usingPublic, publicId, systemId);
		if (retval != null)
		    return retval;;
	    }
	} catch (DoneDelegation x) {
	    // done!
	}
	// step 9 involves returning "no match" 
	return null;
    }


    /**
     * "New Style" parser callback to add an external subset.
     * For documents that don't include an external subset, this may
     * return one according to <em>doctype</em> catalog entries.
     * (This functionality is not a core part of the OASIS XML Catalog
     * specification, though it's presented in an appendix.)
     * If no such entry is defined, this returns null to indicate that
     * this document will not be modified to include such a subset.
     * Calls to this method prevent explicit loading of additional catalogs
     * using {@link #loadCatalog loadCatalog()}.
     *
     * <p><em>Warning:</em> That catalog functionality can be dangerous.
     * It can provide definitions of general entities, and thereby mask
     * certain well formedess errors.
     *
     * @param name Name of the document element, either as declared in
     *	a DOCTYPE declaration or as observed in the text.
     * @param baseURI Document's base URI (absolute).
     *
     * @return Input source for accessing the external subset, or null
     *	if no mapping was found.  The input source may have opened
     *	the stream, and will have a fully resolved URI.
     */
    public InputSource getExternalSubset (String name, String baseURI)
    throws SAXException, IOException
    {
	if (loadingPermitted)
	    disableLoading ();
	try {
	    for (int i = 0; i < catalogs.length; i++) {
		InputSource retval = catalogs [i].getExternalSubset (name);
		if (retval != null)
		    return retval;
	    }
	} catch (DoneDelegation x) {
	    // done!
	}
	return null;
    }


    /**
     * "Old Style" external entity resolution for parsers.
     * This API provides only core functionality.
     * Calls to this method prevent explicit loading of additional catalogs
     * using {@link #loadCatalog loadCatalog()}.
     *
     * <p>The functional limitations of this interface include:</p><ul>
     *
     *	<li>Since system IDs will be absolutized before the resolver
     *	sees them, matching against relative URIs won't work.
     *	This may affect <em>system</em>, <em>rewriteSystem</em>,
     *	and <em>delegateSystem</em> catalog entries.
     *
     *	<li>Because of that absolutization, documents declaring entities
     *	with system IDs using URI schemes that the JVM does not recognize
     *	may be unparsable.  URI schemes such as <em>file:/</em>,
     *	<em>http://</em>, <em>https://</em>, and <em>ftp://</em>
     *	will usually work reliably.
     *
     *	<li>Because missing external subsets can't be provided, the
     *	<em>doctype</em> catalog entries will be ignored.
     *	(The {@link #getExternalSubset getExternalSubset()} method is
     *	a "New Style" resolution option.)
     *
     *	</ul>
     *
     * <p>Applications can tell whether this limited functionality will be
     * used: if the feature flag associated with the {@link EntityResolver2}
     * interface is not <em>true</em>, the limitations apply.  Applications
     * can't usually know whether a given document and catalog will trigger
     * those limitations.  The issue can only be bypassed by operational
     * procedures such as not using catalogs or documents which involve
     * those features.
     *
     * @param publicId Either a normalized public ID, or null
     * @param systemId Always an absolute URI.
     *
     * @return Input source for accessing the external entity, or null
     *	if no mapping was found.  The input source may have opened
     *	the stream, and will have a fully resolved URI.
     */
    final public InputSource resolveEntity (String publicId, String systemId)
    throws SAXException, IOException
    {
	return resolveEntity (null, publicId, null, systemId);
    }


    /**
     * Resolves a URI reference that's not defined to the DTD.
     * This is intended for use with URIs found in document text, such as
     * <em>xml-stylesheet</em> processing instructions and in attribute
     * values, where they are not recognized as URIs by XML parsers.
     * Calls to this method prevent explicit loading of additional catalogs
     * using {@link #loadCatalog loadCatalog()}.
     *
     * <p>This functionality is supported by the OASIS XML Catalog
     * specification, but will never be invoked by an XML parser.
     * It corresponds closely to functionality for mapping system
     * identifiers for entities declared in DTDs; closely enough that
     * this implementation's default behavior is that they be
     * identical, to minimize potential confusion.
     *
     * <p>This method could be useful when implementing the
     * {@link javax.xml.transform.URIResolver} interface, wrapping the
     * input source in a {@link javax.xml.transform.sax.SAXSource}.
     *
     * @see #isUnified
     * @see #setUnified
     *
     * @param baseURI The relevant base URI as specified by the XML Base
     *	specification.  This recognizes <em>xml:base</em> attributes
     *	as overriding the actual (physical) base URI.
     * @param uri Either an absolute URI, or one relative to baseURI
     *
     * @return Input source for accessing the mapped URI, or null