http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
/*
 * Copyright (c) 2004 World Wide Web Consortium,
 *
 * (Massachusetts Institute of Technology, European Research Consortium for
 * Informatics and Mathematics, Keio University). All Rights Reserved. This
 * work is distributed under the W3C(r) Software License [1] 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.
 *
 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
 */

package org.w3c.dom.ls;


 LSResourceResolver provides a way for applications to 
redirect references to external resources. 

 Applications needing to implement custom handling for external 
resources can implement this interface and register their implementation 
by setting the "resource-resolver" parameter of 
DOMConfiguration objects attached to LSParser 
and LSSerializer. It can also be register on 
DOMConfiguration objects attached to Document 
if the "LS" feature is supported. 

 The LSParser will then allow the application to intercept 
any external entities, including the external DTD subset and external 
parameter entities, before including them. The top-level document entity 
is never passed to the resolveResource method. 

 Many DOM 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 URNs. 

Note:  LSResourceResolver is based on the SAX2 [SAX] EntityResolver 
interface. 

See also the Document Object Model (DOM) Level 3 Load
and Save Specification.

/**
 *  <code>LSResourceResolver</code> provides a way for applications to 
 * redirect references to external resources. 
 * <p> Applications needing to implement custom handling for external 
 * resources can implement this interface and register their implementation 
 * by setting the "resource-resolver" parameter of 
 * <code>DOMConfiguration</code> objects attached to <code>LSParser</code> 
 * and <code>LSSerializer</code>. It can also be register on 
 * <code>DOMConfiguration</code> objects attached to <code>Document</code> 
 * if the "LS" feature is supported. 
 * <p> The <code>LSParser</code> will then allow the application to intercept 
 * any external entities, including the external DTD subset and external 
 * parameter entities, before including them. The top-level document entity 
 * is never passed to the <code>resolveResource</code> method. 
 * <p> Many DOM 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 URNs. 
 * <p ><b>Note:</b>  <code>LSResourceResolver</code> is based on the SAX2 [<a href='http://www.saxproject.org/'>SAX</a>] <code>EntityResolver</code> 
 * interface. 
 * <p>See also the <a href='http://www.w3.org/TR/2004/REC-DOM-Level-3-LS-20040407'>Document Object Model (DOM) Level 3 Load
and Save Specification</a>.
 */
public interface LSResourceResolver {
    
 Allow the application to resolve external resources. 

 The LSParser will call this method before opening any 
external resource, including the external DTD subset, external 
entities referenced within the DTD, and external entities referenced 
within the document element (however, the top-level document entity 
is not passed to this method). The application may then request that 
the LSParser resolve the external resource itself, that 
it use an alternative URI, or that it use an entirely different input 
source. 

 Application writers can use this method to redirect external 
system identifiers to secure and/or local URI, 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). 

Params:
  • type –  The type of the resource being resolved. For XML [XML 1.0] resources 
  (i.e. entities), applications must use the value 
  "http://www.w3.org/TR/REC-xml". For XML Schema [XML Schema Part 1]
  , applications must use the value 
  "http://www.w3.org/2001/XMLSchema". Other types of 
  resources are outside the scope of this specification and therefore 
  should recommend an absolute URI in order to use this method.
  • namespaceURI –  The namespace of the resource being resolved, 
  e.g. the target namespace of the XML Schema [XML Schema Part 1]
   when resolving XML Schema resources.
  • publicId –  The public identifier of the external entity being 
  referenced, or null if no public identifier was 
  supplied or if the resource is not an entity.
  • systemId –  The system identifier, a URI reference [IETF RFC 2396], of the 
  external resource being referenced, or null if no 
  system identifier was supplied.
  • baseURI –  The absolute base URI of the resource being parsed, or 
  null if there is no base URI.
Returns: A LSInput object describing the new input 
  source, or null to request that the parser open a 
  regular URI connection to the resource.
/**
     *  Allow the application to resolve external resources. 
     * <br> The <code>LSParser</code> will call this method before opening any 
     * external resource, including the external DTD subset, external 
     * entities referenced within the DTD, and external entities referenced 
     * within the document element (however, the top-level document entity 
     * is not passed to this method). The application may then request that 
     * the <code>LSParser</code> resolve the external resource itself, that 
     * it use an alternative URI, or that it use an entirely different input 
     * source. 
     * <br> Application writers can use this method to redirect external 
     * system identifiers to secure and/or local URI, 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). 
     * @param type  The type of the resource being resolved. For XML [<a href='http://www.w3.org/TR/2004/REC-xml-20040204'>XML 1.0</a>] resources 
     *   (i.e. entities), applications must use the value 
     *   <code>"http://www.w3.org/TR/REC-xml"</code>. For XML Schema [<a href='http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/'>XML Schema Part 1</a>]
     *   , applications must use the value 
     *   <code>"http://www.w3.org/2001/XMLSchema"</code>. Other types of 
     *   resources are outside the scope of this specification and therefore 
     *   should recommend an absolute URI in order to use this method. 
     * @param namespaceURI  The namespace of the resource being resolved, 
     *   e.g. the target namespace of the XML Schema [<a href='http://www.w3.org/TR/2001/REC-xmlschema-1-20010502/'>XML Schema Part 1</a>]
     *    when resolving XML Schema resources. 
     * @param publicId  The public identifier of the external entity being 
     *   referenced, or <code>null</code> if no public identifier was 
     *   supplied or if the resource is not an entity. 
     * @param systemId  The system identifier, a URI reference [<a href='http://www.ietf.org/rfc/rfc2396.txt'>IETF RFC 2396</a>], of the 
     *   external resource being referenced, or <code>null</code> if no 
     *   system identifier was supplied. 
     * @param baseURI  The absolute base URI of the resource being parsed, or 
     *   <code>null</code> if there is no base URI. 
     * @return  A <code>LSInput</code> object describing the new input 
     *   source, or <code>null</code> to request that the parser open a 
     *   regular URI connection to the resource. 
     */
    public LSInput resolveResource(String type, 
                                   String namespaceURI, 
                                   String publicId, 
                                   String systemId, 
                                   String baseURI);

}