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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 jdk.internal.org.xml.sax;

import java.io.IOException;



Basic interface for resolving entities.


This module, both source code and documentation, is in the
Public Domain, and comes with NO WARRANTY.
See http://www.saxproject.org
for further information.



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 setEntityResolver method.


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.


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 specialized input sources,
or for applications that use URI types other than URLs.


The following resolver would provide the application
with a special character stream for the entity with the system
identifier "http://www.myhost.com/today":


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;
    }
  }
}



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).


Author:David Megginson
See Also:
  • setEntityResolver.setEntityResolver
  • InputSource
Since:SAX 1.0
/**
 * 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 specialized 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
 * @see org.xml.sax.XMLReader#setEntityResolver
 * @see org.xml.sax.InputSource
 */
public interface EntityResolver {


    
Allow the application to resolve external entities.

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).


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.  


If the system identifier is a URL, the SAX parser must
resolve it fully before reporting it to the application.


Params:
  • publicId – The public identifier of the external entity
       being referenced, or null if none was supplied.
  • systemId – The system identifier of the external entity
       being referenced.
Throws:
  • SAXException – Any SAX exception, possibly
           wrapping another exception.
  • IOException – A Java-specific IO exception,
           possibly the result of creating a new InputStream
           or Reader for the InputSource.
See Also:
  • InputSource
Returns:An InputSource object describing the new input source,
        or null to request that the parser open a regular
        URI connection to the system identifier.
/**
     * 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