| /******************************************************************************* |
| * Copyright (c) 2003 IBM Corporation and others. |
| * All rights reserved. This program and the accompanying materials |
| * are made available under the terms of the Common Public License v1.0 |
| * which accompanies this distribution, and is available at |
| * http://www.eclipse.org/legal/cpl-v10.html |
| * |
| * Contributors: |
| * IBM Corporation - initial API and implementation |
| *******************************************************************************/ |
| |
| package org.eclipse.osgi.framework.internal.protocol; |
| |
| import java.io.IOException; |
| import java.net.ContentHandler; |
| import java.net.URLConnection; |
| import org.osgi.framework.*; |
| import org.osgi.service.url.URLConstants; |
| import org.osgi.util.tracker.ServiceTracker; |
| import org.osgi.util.tracker.ServiceTrackerCustomizer; |
| |
| /** |
| * The ContentHandlerProxy is a ContentHandler that acts as a proxy for registered ContentHandlers. |
| * When a ContentHandler is requested from the ContentHandlerFactory and it exists in the service |
| * registry, a ContentHandlerProxy is created which will pass all the requests from the requestor to |
| * the real ContentHandler. We can't return the real ContentHandler from the ContentHandlerFactory |
| * because the JVM caches ContentHandlers and therefore would not support a dynamic environment of |
| * ContentHandlers being registered and unregistered. |
| */ |
| public class ContentHandlerProxy extends ContentHandler implements ServiceTrackerCustomizer { |
| |
| protected ContentHandler realHandler; |
| |
| //TODO avoid type-based names |
| protected ServiceTracker contentHandlerServiceTracker; |
| |
| protected BundleContext context; |
| protected ServiceReference contentHandlerServiceReference; |
| |
| protected String contentType; |
| |
| protected int ranking = -1; |
| |
| public ContentHandlerProxy(String contentType, ServiceReference reference, BundleContext context) { |
| this.context = context; |
| this.contentType = contentType; |
| |
| if (reference != null) { |
| setNewHandler(reference, getRank(reference)); |
| } |
| //In this case, the proxy is constructed for a Content Handler that is not currently registered. |
| //Use the DefaultContentHandler until a ContentHandler for this mime-type is registered |
| else { |
| realHandler = new DefaultContentHandler(); |
| } |
| contentHandlerServiceTracker = new ServiceTracker(context, ContentHandler.class.getName(), this); |
| contentHandlerServiceTracker.open(); |
| } |
| |
| private void setNewHandler(ServiceReference reference, int rank) { |
| this.contentHandlerServiceReference = reference; |
| Object property = reference.getProperty(Constants.SERVICE_RANKING); |
| this.ranking = rank; |
| this.realHandler = (ContentHandler) context.getService(reference); |
| } |
| |
| /** |
| * @see org.osgi.util.tracker.ServiceTrackerCustomizer#addingService(ServiceReference) |
| */ |
| public Object addingService(ServiceReference reference) { |
| //check to see if our contentType is being registered by another service |
| String[] contentTypes = (String[]) reference.getProperty(URLConstants.URL_CONTENT_MIMETYPE); |
| for (int i = 0; i < contentTypes.length; i++) { |
| if (contentTypes[i].equals(contentType)) { |
| //If our contentType is registered by another service, check the service ranking and switch |
| //URLStreamHandlers if nessecary. |
| |
| int newServiceRanking = getRank(reference); |
| |
| //int newServiceRanking = ((Integer)reference.getProperty(Constants.SERVICE_RANKING)).intValue(); |
| if (newServiceRanking > ranking) { |
| setNewHandler(reference, newServiceRanking); |
| } |
| return (reference); |
| } |
| } |
| |
| //we don't want to continue hearing events about a ContentHandler service not registered under our contentType |
| return (null); |
| } |
| |
| /** |
| * @see org.osgi.util.tracker.ServiceTrackerCustomizer#modifiedService(ServiceReference, Object) |
| */ |
| |
| public void modifiedService(ServiceReference reference, Object service) { |
| int newrank = getRank(reference); |
| |
| if (reference == contentHandlerServiceReference) { |
| if (newrank < ranking) //The ContentHandler we are currently |
| //using has dropped it's ranking below a ContentHandler registered for the same protocol. |
| //We need to swap out ContentHandlers. |
| //this should get us the highest ranked service, if available |
| { |
| ServiceReference newReference = contentHandlerServiceTracker.getServiceReference(); |
| if (newReference != contentHandlerServiceReference && newReference != null) { |
| setNewHandler(newReference, ((Integer) newReference.getProperty(Constants.SERVICE_RANKING)).intValue()); |
| } |
| } |
| } else if (newrank > ranking) //the service changed is another URLHandler that we are not currently using |
| //If it's ranking is higher, we must swap it in. |
| { |
| setNewHandler(reference, newrank); |
| } |
| |
| } |
| |
| /** |
| * @see org.osgi.util.tracker.ServiceTrackerCustomizer#removedService(ServiceReference, Object) |
| */ |
| public void removedService(ServiceReference reference, Object service) { |
| //check to see if our URLStreamHandler was unregistered. If so, look |
| //for a lower ranking URLHandler |
| //TODO invert test and return quickly, to reduce indentation |
| if (reference == contentHandlerServiceReference) { |
| //this should get us the highest ranking service left, if available |
| ServiceReference newReference = contentHandlerServiceTracker.getServiceReference(); |
| if (newReference != null) { |
| setNewHandler(newReference, getRank(newReference)); |
| } else { |
| ranking = -1; |
| realHandler = new DefaultContentHandler(); |
| } |
| |
| } |
| |
| } |
| |
| /** |
| * @see java.net.ContentHandler#getContent(URLConnection) |
| */ |
| |
| public Object getContent(URLConnection uConn) throws IOException { |
| return realHandler.getContent(uConn); |
| } |
| |
| private int getRank(ServiceReference reference) { |
| Object property = reference.getProperty(Constants.SERVICE_RANKING); |
| return (property instanceof Integer) ? ((Integer) property).intValue() : 0; |
| } |
| |
| class DefaultContentHandler extends ContentHandler { |
| |
| /** |
| * @see java.net.ContentHandler#getContent(URLConnection) |
| */ |
| public Object getContent(URLConnection uConn) throws IOException { |
| return uConn.getInputStream(); |
| } |
| } |
| } |