Copyright (c) 2003, 2018 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2003, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/

package org.eclipse.osgi.internal.url;

import java.lang.reflect.Method;
import java.net.ContentHandler;
import java.net.URLConnection;
import java.util.Arrays;
import java.util.Hashtable;
import java.util.List;
import java.util.Map;
import java.util.StringTokenizer;
import org.eclipse.osgi.framework.log.FrameworkLogEntry;
import org.eclipse.osgi.internal.framework.EquinoxContainer;
import org.eclipse.osgi.internal.messages.Msg;
import org.eclipse.osgi.util.NLS;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;
import org.osgi.service.url.URLConstants;
import org.osgi.util.tracker.ServiceTracker;

The ContentHandlerFactory is registered with the JVM to provide content handlers
to requestors.  The ContentHandlerFactory will first look for built-in content handlers.
If a built in handler exists, this factory will return null.  Otherwise, this ContentHandlerFactory
will search the service registry for a maching Content-Handler and, if found, return a 
proxy for that content handler.
/**
 * The ContentHandlerFactory is registered with the JVM to provide content handlers
 * to requestors.  The ContentHandlerFactory will first look for built-in content handlers.
 * If a built in handler exists, this factory will return null.  Otherwise, this ContentHandlerFactory
 * will search the service registry for a maching Content-Handler and, if found, return a 
 * proxy for that content handler.
 */
public class ContentHandlerFactoryImpl extends MultiplexingFactory implements java.net.ContentHandlerFactory {
	private ServiceTracker<ContentHandler, ContentHandler> contentHandlerTracker;

	private static final String contentHandlerClazz = "java.net.ContentHandler"; //$NON-NLS-1$
	private static final String CONTENT_HANDLER_PKGS = "java.content.handler.pkgs"; //$NON-NLS-1$
	private static final String DEFAULT_VM_CONTENT_HANDLERS = "sun.net.www.content|sun.awt.www.content"; //$NON-NLS-1$

	private static final List<Class<?>> ignoredClasses = Arrays.asList(new Class<?>[] {MultiplexingContentHandler.class, ContentHandlerFactoryImpl.class, URLConnection.class});

	private Map<String, ContentHandlerProxy> proxies;
	private java.net.ContentHandlerFactory parentFactory;

	public ContentHandlerFactoryImpl(BundleContext context, EquinoxContainer container) {
		super(context, container);

		proxies = new Hashtable<>(5);

		//We need to track content handler registrations
		contentHandlerTracker = new ServiceTracker<>(context, contentHandlerClazz, null);
		contentHandlerTracker.open();
	}

	
See Also:
createContentHandler.createContentHandler(String)/**
	 * @see java.net.ContentHandlerFactory#createContentHandler(String)
	 */
	//TODO method is too long... consider reducing indentation (returning quickly) and moving complex steps to private methods
	@Override
	public ContentHandler createContentHandler(String contentType) {
		//first, we check to see if there exists a built in content handler for
		//this content type.  we can not overwrite built in ContentHandlers
		String builtInHandlers = URLStreamHandlerFactoryImpl.secureAction.getProperty(CONTENT_HANDLER_PKGS);
		builtInHandlers = builtInHandlers == null ? DEFAULT_VM_CONTENT_HANDLERS : DEFAULT_VM_CONTENT_HANDLERS + '|' + builtInHandlers;
		Class<?> clazz = null;
		if (builtInHandlers != null) {
			//replace '/' with a '.' and all characters not allowed in a java class name
			//with a '_'.

			// find all characters not allowed in java names
			String convertedContentType = contentType.replace('.', '_');
			convertedContentType = convertedContentType.replace('/', '.');
			convertedContentType = convertedContentType.replace('-', '_');
			StringTokenizer tok = new StringTokenizer(builtInHandlers, "|"); //$NON-NLS-1$
			while (tok.hasMoreElements()) {
				StringBuilder name = new StringBuilder();
				name.append(tok.nextToken());
				name.append("."); //$NON-NLS-1$
				name.append(convertedContentType);
				try {
					clazz = URLStreamHandlerFactoryImpl.secureAction.loadSystemClass(name.toString());
					if (clazz != null) {
						return (null); //this class exists, it is a built in handler, let the JVM handle it	
					}
				} catch (ClassNotFoundException ex) {
					//keep looking
				}
			}
		}

		if (isMultiplexing())
			return new MultiplexingContentHandler(contentType, this);

		return createInternalContentHandler(contentType);
	}

	public ContentHandler createInternalContentHandler(String contentType) {
		//first check to see if the handler is in the cache
		ContentHandlerProxy proxy = proxies.get(contentType);
		if (proxy != null) {
			return (proxy);
		}
		ServiceReference<ContentHandler>[] serviceReferences = contentHandlerTracker.getServiceReferences();
		if (serviceReferences != null) {
			for (ServiceReference<ContentHandler> serviceReference : serviceReferences) {
				Object prop = serviceReference.getProperty(URLConstants.URL_CONTENT_MIMETYPE);
				if (prop instanceof String)
					prop = new String[] {(String) prop}; // TODO should this be a warning?
				if (!(prop instanceof String[])) {
					String message = NLS.bind(Msg.URL_HANDLER_INCORRECT_TYPE, new Object[]{URLConstants.URL_CONTENT_MIMETYPE, contentHandlerClazz, serviceReference.getBundle()});
					container.getLogServices().log(EquinoxContainer.NAME, FrameworkLogEntry.WARNING, message, null);
					continue;
				}
				String[] contentHandler = (String[]) prop;
				for (String typename : contentHandler) {
					if (typename.equals(contentType)) {
						proxy = new ContentHandlerProxy(contentType, serviceReference, context);
						proxies.put(contentType, proxy);
						return (proxy);
					}
				}
			}
		}
		// if parent is present do parent lookup before returning a proxy
		if (parentFactory != null) {
			ContentHandler parentHandler = parentFactory.createContentHandler(contentType);
			if (parentHandler != null)
				return parentHandler;
		}
		//If we can't find the content handler in the service registry, return Proxy with DefaultContentHandler set.
		//We need to do this because if we return null, we won't get called again for this content type.
		proxy = new ContentHandlerProxy(contentType, null, context);
		proxies.put(contentType, proxy);
		return (proxy);
	}

	public synchronized ContentHandler findAuthorizedContentHandler(String contentType) {
		Object factory = findAuthorizedFactory(ignoredClasses);
		if (factory == null)
			return null;

		if (factory == this)
			return createInternalContentHandler(contentType);

		try {
			Method createInternalContentHandlerMethod = factory.getClass().getMethod("createInternalContentHandler", new Class[] {String.class}); //$NON-NLS-1$
			return (ContentHandler) createInternalContentHandlerMethod.invoke(factory, new Object[] {contentType});
		} catch (Exception e) {
			container.getLogServices().log(ContentHandlerFactoryImpl.class.getName(), FrameworkLogEntry.ERROR, "findAuthorizedContentHandler-loop", e); //$NON-NLS-1$
			throw new RuntimeException(e.getMessage(), e);
		}
	}

	@Override
	public Object getParentFactory() {
		return parentFactory;
	}

	@Override
	public void setParentFactory(Object parentFactory) {
		if (this.parentFactory == null) // only allow it to be set once
			this.parentFactory = (java.net.ContentHandlerFactory) parentFactory;
	}
}