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jeremybenn |
// SAX entity resolver.
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// http://www.saxproject.org
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// No warranty; no copyright -- use this as you will.
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// $Id: EntityResolver.java,v 1.1 2004/12/23 22:38:42 mark Exp $
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package org.xml.sax;
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import java.io.IOException;
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/**
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* Basic interface for resolving entities.
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*
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* <blockquote>
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* <em>This module, both source code and documentation, is in the
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* Public Domain, and comes with <strong>NO WARRANTY</strong>.</em>
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* See <a href='http://www.saxproject.org'>http://www.saxproject.org</a>
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* for further information.
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* </blockquote>
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*
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* <p>If a SAX application needs to implement customized handling
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* for external entities, it must implement this interface and
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* register an instance with the SAX driver using the
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* {@link org.xml.sax.XMLReader#setEntityResolver setEntityResolver}
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* method.</p>
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*
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* <p>The XML reader will then allow the application to intercept any
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* external entities (including the external DTD subset and external
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* parameter entities, if any) before including them.</p>
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*
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* <p>Many SAX applications will not need to implement this interface,
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* but it will be especially useful for applications that build
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* XML documents from databases or other specialised input sources,
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* or for applications that use URI types other than URLs.</p>
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*
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* <p>The following resolver would provide the application
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* with a special character stream for the entity with the system
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* identifier "http://www.myhost.com/today":</p>
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*
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* <pre>
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* import org.xml.sax.EntityResolver;
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* import org.xml.sax.InputSource;
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*
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* public class MyResolver implements EntityResolver {
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* public InputSource resolveEntity (String publicId, String systemId)
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* {
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* if (systemId.equals("http://www.myhost.com/today")) {
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* // return a special input source
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* MyReader reader = new MyReader();
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* return new InputSource(reader);
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* } else {
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* // use the default behaviour
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* return null;
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* }
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* }
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* }
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* </pre>
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*
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* <p>The application can also use this interface to redirect system
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* identifiers to local URIs or to look up replacements in a catalog
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* (possibly by using the public identifier).</p>
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*
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* @since SAX 1.0
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* @author David Megginson
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* @version 2.0.1 (sax2r2)
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* @see org.xml.sax.XMLReader#setEntityResolver
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* @see org.xml.sax.InputSource
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*/
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public interface EntityResolver {
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/**
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* Allow the application to resolve external entities.
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*
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* <p>The parser will call this method before opening any external
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* entity except the top-level document entity. Such entities include
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* the external DTD subset and external parameter entities referenced
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* within the DTD (in either case, only if the parser reads external
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* parameter entities), and external general entities referenced
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* within the document element (if the parser reads external general
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* entities). The application may request that the parser locate
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* the entity itself, that it use an alternative URI, or that it
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* use data provided by the application (as a character or byte
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* input stream).</p>
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*
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* <p>Application writers can use this method to redirect external
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* system identifiers to secure and/or local URIs, to look up
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* public identifiers in a catalogue, or to read an entity from a
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* database or other input source (including, for example, a dialog
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* box). Neither XML nor SAX specifies a preferred policy for using
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* public or system IDs to resolve resources. However, SAX specifies
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* how to interpret any InputSource returned by this method, and that
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* if none is returned, then the system ID will be dereferenced as
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* a URL. </p>
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*
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* <p>If the system identifier is a URL, the SAX parser must
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* resolve it fully before reporting it to the application.</p>
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*
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* @param publicId The public identifier of the external entity
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* being referenced, or null if none was supplied.
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* @param systemId The system identifier of the external entity
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* being referenced.
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* @return An InputSource object describing the new input source,
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* or null to request that the parser open a regular
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* URI connection to the system identifier.
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* @exception org.xml.sax.SAXException Any SAX exception, possibly
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* wrapping another exception.
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* @exception java.io.IOException A Java-specific IO exception,
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* possibly the result of creating a new InputStream
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* or Reader for the InputSource.
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* @see org.xml.sax.InputSource
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*/
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public abstract InputSource resolveEntity (String publicId,
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String systemId)
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throws SAXException, IOException;
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}
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// end of EntityResolver.java
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