Java tutorial
/* * Copyright (c) 2004, 2005, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code 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 * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ // EntityResolver2.java - Extended SAX entity resolver. // http://www.saxproject.org // No warranty; no copyright -- use this as you will. // $Id: EntityResolver2.java,v 1.2 2004/11/03 22:49:08 jsuttor Exp $ package org.xml.sax.ext; import java.io.IOException; import org.xml.sax.EntityResolver; import org.xml.sax.InputSource; import org.xml.sax.XMLReader; import org.xml.sax.SAXException; /** * Extended interface for mapping external entity references to input * sources, or providing a missing external subset. The * {@link XMLReader#setEntityResolver XMLReader.setEntityResolver()} method * is used to provide implementations of this interface to parsers. * When a parser uses the methods in this interface, the * {@link EntityResolver2#resolveEntity EntityResolver2.resolveEntity()} * method (in this interface) is used <em>instead of</em> the older (SAX 1.0) * {@link EntityResolver#resolveEntity EntityResolver.resolveEntity()} method. * * <blockquote> * <em>This module, both source code and documentation, is in the * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em> * </blockquote> * * <p>If a SAX application requires the customized handling which this * interface defines for external entities, it must ensure that it uses * an XMLReader with the * <em>http://xml.org/sax/features/use-entity-resolver2</em> feature flag * set to <em>true</em> (which is its default value when the feature is * recognized). If that flag is unrecognized, or its value is false, * or the resolver does not implement this interface, then only the * {@link EntityResolver} method will be used. * * <p>That supports three categories of application that modify entity * resolution. <em>Old Style</em> applications won't know about this interface; * they will provide an EntityResolver. * <em>Transitional Mode</em> provide an EntityResolver2 and automatically * get the benefit of its methods in any systems (parsers or other tools) * supporting it, due to polymorphism. * Both <em>Old Style</em> and <em>Transitional Mode</em> applications will * work with any SAX2 parser. * <em>New style</em> applications will fail to run except on SAX2 parsers * that support this particular feature. * They will insist that feature flag have a value of "true", and the * EntityResolver2 implementation they provide might throw an exception * if the original SAX 1.0 style entity resolution method is invoked. * * @see org.xml.sax.XMLReader#setEntityResolver * * @since 1.5, SAX 2.0 (extensions 1.1 alpha) * @author David Brownell */ public interface EntityResolver2 extends EntityResolver { /** * Allows applications to provide an external subset for documents * that don't explicitly define one. Documents with DOCTYPE declarations * that omit an external subset can thus augment the declarations * available for validation, entity processing, and attribute processing * (normalization, defaulting, and reporting types including ID). * This augmentation is reported * through the {@link LexicalHandler#startDTD startDTD()} method as if * the document text had originally included the external subset; * this callback is made before any internal subset data or errors * are reported. * * <p>This method can also be used with documents that have no DOCTYPE * declaration. When the root element is encountered, * but no DOCTYPE declaration has been seen, this method is * invoked. If it returns a value for the external subset, that root * element is declared to be the root element, giving the effect of * splicing a DOCTYPE declaration at the end the prolog of a document * that could not otherwise be valid. The sequence of parser callbacks * in that case logically resembles this: * * <pre> * ... comments and PIs from the prolog (as usual) * startDTD ("rootName", source.getPublicId (), source.getSystemId ()); * startEntity ("[dtd]"); * ... declarations, comments, and PIs from the external subset * endEntity ("[dtd]"); * endDTD (); * ... then the rest of the document (as usual) * startElement (..., "rootName", ...); * </pre> * * <p>Note that the InputSource gets no further resolution. * Implementations of this method may wish to invoke * {@link #resolveEntity resolveEntity()} to gain benefits such as use * of local caches of DTD entities. Also, this method will never be * used by a (non-validating) processor that is not including external * parameter entities. * * <p>Uses for this method include facilitating data validation when * interoperating with XML processors that would always require * undesirable network accesses for external entities, or which for * other reasons adopt a "no DTDs" policy. * Non-validation motives include forcing documents to include DTDs so * that attributes are handled consistently. * For example, an XPath processor needs to know which attibutes have * type "ID" before it can process a widely used type of reference. * * <p><strong>Warning:</strong> Returning an external subset modifies * the input document. By providing definitions for general entities, * it can make a malformed document appear to be well formed. * * @param name Identifies the document root element. This name comes * from a DOCTYPE declaration (where available) or from the actual * root element. * @param baseURI The document's base URI, serving as an additional * hint for selecting the external subset. This is always an absolute * URI, unless it is null because the XMLReader was given an InputSource * without one. * * @return An InputSource object describing the new external subset * to be used by the parser, or null to indicate that no external * subset is provided. * * @exception SAXException Any SAX exception, possibly wrapping * another exception. * @exception IOException Probably indicating a failure to create * a new InputStream or Reader, or an illegal URL. */ public InputSource getExternalSubset(String name, String baseURI) throws SAXException, IOException; /** * Allows applications to map references to external entities into input * sources, or tell the parser it should use conventional URI resolution. * This method is only called for external entities which have been * properly declared. * This method provides more flexibility than the {@link EntityResolver} * interface, supporting implementations of more complex catalogue * schemes such as the one defined by the <a href= * "http://www.oasis-open.org/committees/entity/spec-2001-08-06.html" * >OASIS XML Catalogs</a> specification. * * <p>Parsers configured to use this resolver method will call it * to determine the input source to use for any external entity * being included because of a reference in the XML text. * That excludes the document entity, and any external entity returned * by {@link #getExternalSubset getExternalSubset()}. * When a (non-validating) processor is configured not to include * a class of entities (parameter or general) through use of feature * flags, this method is not invoked for such entities. * * <p>Note that the entity naming scheme used here is the same one * used in the {@link LexicalHandler}, or in the {@link * org.xml.sax.ContentHandler#skippedEntity * ContentHandler.skippedEntity()} * method. * * @param name Identifies the external entity being resolved. * Either "[dtd]" for the external subset, or a name starting * with "%" to indicate a parameter entity, or else the name of * a general entity. This is never null when invoked by a SAX2 * parser. * @param publicId The public identifier of the external entity being * referenced (normalized as required by the XML specification), or * null if none was supplied. * @param baseURI The URI with respect to which relative systemIDs * are interpreted. This is always an absolute URI, unless it is * null (likely because the XMLReader was given an InputSource without * one). This URI is defined by the XML specification to be the one * associated with the "{@literal <}" starting the relevant declaration. * @param systemId The system identifier of the external entity * being referenced; either a relative or absolute URI. * This is never null when invoked by a SAX2 parser; only declared * entities, and any external subset, are resolved by such parsers. * * @return An InputSource object describing the new input source to * be used by the parser. Returning null directs the parser to * resolve the system ID against the base URI and open a connection * to resulting URI. * * @exception SAXException Any SAX exception, possibly wrapping * another exception. * @exception IOException Probably indicating a failure to create * a new InputStream or Reader, or an illegal URL. */ public InputSource resolveEntity(String name, String publicId, String baseURI, String systemId) throws SAXException, IOException; }