Entity manager that is (when registered) validates Smooks XML files

SmooksEntityManager.java

/*
 * Milyn - Copyright (C) 2006 - 2011
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License (version 2.1) as published by the Free Software
 * Foundation.
 *
 * This library 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 Lesser General Public License for more details:
 * http://www.gnu.org/licenses/lgpl.txt
 */
package org.talend.test;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import org.apache.xerces.impl.XMLEntityManager;
import org.apache.xerces.xni.XMLResourceIdentifier;
import org.apache.xerces.xni.XNIException;
import org.apache.xerces.xni.parser.XMLEntityResolver;
import org.apache.xerces.xni.parser.XMLInputSource;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.filter.ElementFilter;
import org.jdom.input.SAXBuilder;
import org.milyn.util.ClassUtil;

/**
 * Extension of Xerces {@link XMLEntityManager} that implements
 * {@link XMLEntityResolver} which additinally
 * able to resolve Smooks XML Schemas
 * 
 * @author zubairov
 */
public class SmooksEntityManager extends XMLEntityManager {

	private final Map<String, String> catalog;
	
	private static final Map<String, XMLInputSource> cache = new HashMap<String, XMLInputSource>();

	/**
	 * Factory method to create a new instance
	 * 
	 * @return
	 * @throws IOException 
	 */
	public static SmooksEntityManager createInstance() throws IOException {
        List<URL> urnFiles = ClassUtil.getResources("/plugin.xml", SmooksEntityManager.class);
        Map<String, String> catalog = new HashMap<String, String>();
		for (URL url : urnFiles) {
			InputStream in = url.openStream();
			try {
				if (in != null) {
					SAXBuilder builder = new SAXBuilder();
					Document document = builder.build(in);
					@SuppressWarnings("unchecked")
					Iterator<Element> it = document.getDescendants(new ElementFilter("uri"));
					while(it.hasNext()) {
						Element next = it.next();
						String uri = next.getAttributeValue("uri");
						String name = next.getAttributeValue("name");
						catalog.put(name, "/" + uri);
					}
				}
			} catch (JDOMException e) {
				e.printStackTrace();
			} finally {
				if (in != null) {
					in.close();
				}
			}
		}
		// One resource we have to add manually
		catalog.put("urn:org.milyn.edi.unedifact.v41", "/META-INF/schema/v41-segments.xsd");
        return new SmooksEntityManager(catalog);
	}

	/**
	 * Constructor called from {@link #createInstance()} with Map
	 * NamespaceURI --> ResourceLocation
	 * 
	 * @param catalog
	 */
	protected SmooksEntityManager(Map<String, String> catalog) {
		super();
		this.catalog = catalog;
	}
	
	@Override
	public XMLInputSource resolveEntity(XMLResourceIdentifier resourceIdentifier)
			throws IOException, XNIException {
		XMLInputSource result = super.resolveEntity(resourceIdentifier);
		if (result.getPublicId() == null && result.getSystemId() == null
				&& result.getCharacterStream() == null
				&& result.getByteStream() == null) {
			String ns = resourceIdentifier.getNamespace();
			if (ns != null) {
				if (catalog.containsKey(ns)) {
					result = cache.get(ns);
					if (result == null) {
						result = new XMLInputSource(resourceIdentifier);
						String location = catalog.get(ns);
						InputStream stream = SmooksEntityManager.class.getResourceAsStream(location);
						if (stream == null) {
							throw new XNIException("Smooks Entity Manager was unable to find resource with location: " + location);
						}
						result.setByteStream(stream);
						cache.put(ns, result);
					}
				} else {
					throw new XNIException("Can't find schema with NS: " + ns);
				}
			}
		}
		return result;
	}
	
}