// 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 2002/01/12 19:20:08 dbrownell Exp $
package org.xml.sax.ext;
import java.io.IOException;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
/**
* 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>
*
* <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.
* </p>
*
* @see org.xml.sax.XMLReader#setEntityResolver
*
* @since SAX 2.0 (extensions 1.1 alpha)
* @author David Brownell
* @version TBD
*/
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>
*
* <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:</p>
*
* <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>
*
* <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>
*
* <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.
* </p>
*
* @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>
*
* <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>
*
* <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. </p>
*
* @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 "<" 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;
}