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Nuts'n'Bolts Utilities
There is a newer version: 6.2.0
/*
 * Copyright (c) 2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, 2020 David Berkman
 *
 * This file is part of the SmallMind Code Project.
 *
 * The SmallMind Code Project is free software, you can redistribute
 * it and/or modify it under either, at your discretion...
 *
 * 1) The terms of GNU Affero General Public License as published by the
 * Free Software Foundation, either version 3 of the License, or (at
 * your option) any later version.
 *
 * ...or...
 *
 * 2) The terms of the Apache License, Version 2.0.
 *
 * The SmallMind Code Project is distributed 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. See the GNU
 * General Public License or Apache License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * and the Apache License along with the SmallMind Code Project. If not, see
 *  or .
 *
 * Additional permission under the GNU Affero GPL version 3 section 7
 * ------------------------------------------------------------------
 * If you modify this Program, or any covered work, by linking or
 * combining it with other code, such other code is not for that reason
 * alone subject to any of the requirements of the GNU Affero GPL
 * version 3.
 */
package org.smallmind.nutsnbolts.xml;

import java.io.InputStream;
import javax.xml.transform.Source;
import javax.xml.transform.TransformerException;
import javax.xml.transform.URIResolver;
import javax.xml.transform.stream.StreamSource;
import org.smallmind.nutsnbolts.resource.Resource;

public class XMLURIResolver implements URIResolver {

  private static XMLURIResolver URI_RESOLVER;

  private final ProtocolResolver protocolResolver;

  public XMLURIResolver (ProtocolResolver protocolResolver) {

    this.protocolResolver = protocolResolver;
  }

  public synchronized static XMLURIResolver getInstance () {

    if (URI_RESOLVER == null) {
      URI_RESOLVER = new XMLURIResolver(SmallMindProtocolResolver.getInstance());
    }

    return URI_RESOLVER;
  }

  public Source resolve (String href, String baseHref)
    throws TransformerException {

    Resource uriResource;
    InputStream uriStream;

    try {
      if ((uriResource = protocolResolver.resolve(href)) != null) {
        if ((uriStream = uriResource.getInputStream()) != null) {
          return new StreamSource(uriStream);
        }
      }
    } catch (Exception exception) {
      throw new TransformerException(exception);
    }

    return null;
  }
}