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// SAX entity resolver. // http://www.saxproject.org // No warranty; no copyright -- use this as you will. // $Id: EntityResolver.java,v 1.2 2004/11/03 22:44:52 jsuttor Exp $ package org.xml.sax; import java.io.IOException; /** * Basic interface for resolving entities. * * <blockquote> * <em>This module, both source code and documentation, is in the * Public Domain, and comes with <strong>NO WARRANTY</strong>.</em> * See <a href='http://www.saxproject.org'>http://www.saxproject.org</a> * for further information. * </blockquote> * * <p>If a SAX application needs to implement customized handling * for external entities, it must implement this interface and * register an instance with the SAX driver using the * {@link org.xml.sax.XMLReader#setEntityResolver setEntityResolver} * method.</p> * * <p>The XML reader will then allow the application to intercept any * external entities (including the external DTD subset and external * parameter entities, if any) before including them.</p> * * <p>Many SAX applications will not need to implement this interface, * but it will be especially useful for applications that build * XML documents from databases or other specialised input sources, * or for applications that use URI types other than URLs.</p> * * <p>The following resolver would provide the application * with a special character stream for the entity with the system * identifier "http://www.myhost.com/today":</p> * * <pre> * import org.xml.sax.EntityResolver; * import org.xml.sax.InputSource; * * public class MyResolver implements EntityResolver { * public InputSource resolveEntity (String publicId, String systemId) * { * if (systemId.equals("http://www.myhost.com/today")) { * // return a special input source * MyReader reader = new MyReader(); * return new InputSource(reader); * } else { * // use the default behaviour * return null; * } * } * } * </pre> * * <p>The application can also use this interface to redirect system * identifiers to local URIs or to look up replacements in a catalog * (possibly by using the public identifier).</p> * * @since SAX 1.0 * @author David Megginson * @version 2.0.1 (sax2r2) * @see org.xml.sax.XMLReader#setEntityResolver * @see org.xml.sax.InputSource */ public interface EntityResolver { /** * Allow the application to resolve external entities. * * <p>The parser will call this method before opening any external * entity except the top-level document entity. Such entities include * the external DTD subset and external parameter entities referenced * within the DTD (in either case, only if the parser reads external * parameter entities), and external general entities referenced * within the document element (if the parser reads external general * entities). The application may request that the parser locate * the entity itself, that it use an alternative URI, or that it * use data provided by the application (as a character or byte * input stream).</p> * * <p>Application writers can use this method to redirect external * system identifiers to secure and/or local URIs, to look up * public identifiers in a catalogue, or to read an entity from a * database or other input source (including, for example, a dialog * box). Neither XML nor SAX specifies a preferred policy for using * public or system IDs to resolve resources. However, SAX specifies * how to interpret any InputSource returned by this method, and that * if none is returned, then the system ID will be dereferenced as * a URL. </p> * * <p>If the system identifier is a URL, the SAX parser must * resolve it fully before reporting it to the application.</p> * * @param publicId The public identifier of the external entity * being referenced, or null if none was supplied. * @param systemId The system identifier of the external entity * being referenced. * @return An InputSource object describing the new input source, * or null to request that the parser open a regular * URI connection to the system identifier. * @exception org.xml.sax.SAXException Any SAX exception, possibly * wrapping another exception. * @exception java.io.IOException A Java-specific IO exception, * possibly the result of creating a new InputStream * or Reader for the InputSource. * @see org.xml.sax.InputSource */ public abstract InputSource resolveEntity (String publicId, String systemId) throws SAXException, IOException; } // end of EntityResolver.java