Richard S. Hall | 515592e | 2005-11-08 08:57:20 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2005 The Apache Software Foundation |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | * |
| 16 | */ |
| 17 | package org.apache.felix.framework; |
| 18 | |
| 19 | import java.io.IOException; |
| 20 | import java.net.ContentHandler; |
| 21 | import java.net.URLConnection; |
| 22 | import java.util.HashMap; |
| 23 | import java.util.Map; |
| 24 | |
| 25 | import org.osgi.framework.BundleContext; |
| 26 | import org.osgi.service.url.URLConstants; |
| 27 | |
| 28 | /** |
| 29 | * <p> |
| 30 | * This class implements a content handler proxy. When the content handler |
| 31 | * proxy instance is created, it is associated with a particular mime type |
| 32 | * and will answer all future requests for content of that type. It does |
| 33 | * not directly handle the content requests, but delegates the requests to |
| 34 | * an underlying content handler service. |
| 35 | * </p> |
| 36 | * <p> |
| 37 | * The proxy for a particular mime type is used for all framework instances |
| 38 | * that may contain their own content handler services. When performing a |
| 39 | * content handler operation, the proxy retrieves the handler service from |
| 40 | * the framework instance associated with the current call stack and delegates |
| 41 | * the call to the handler service. |
| 42 | * </p> |
| 43 | * <p> |
| 44 | * The proxy will create simple content handler service trackers for each |
| 45 | * framework instance. The trackers will listen to service events in its |
| 46 | * respective framework instance to maintain a reference to the "best" |
| 47 | * content handler service at any given time. |
| 48 | * </p> |
| 49 | **/ |
| 50 | class URLHandlersContentHandlerProxy extends ContentHandler |
| 51 | { |
| 52 | private Map m_trackerMap = new HashMap(); |
| 53 | private String m_mimeType = null; |
| 54 | |
| 55 | public URLHandlersContentHandlerProxy(String mimeType) |
| 56 | { |
| 57 | m_mimeType = mimeType; |
| 58 | } |
| 59 | |
| 60 | // |
| 61 | // ContentHandler interface method. |
| 62 | // |
| 63 | |
| 64 | public synchronized Object getContent(URLConnection urlc) throws IOException |
| 65 | { |
| 66 | ContentHandler svc = getContentHandlerService(); |
| 67 | if (svc == null) |
| 68 | { |
| 69 | throw new IOException("Content handler unavailable: " |
| 70 | + urlc.getContentType()); |
| 71 | } |
| 72 | return svc.getContent(urlc); |
| 73 | } |
| 74 | |
| 75 | /** |
| 76 | * <p> |
| 77 | * Private method to retrieve the content handler service from the |
| 78 | * framework instance associated with the current call stack. A |
| 79 | * simple service tracker is created and cached for the associated |
| 80 | * framework instance when this method is called. |
| 81 | * </p> |
| 82 | * @return the content handler service from the framework instance |
| 83 | * associated with the current call stack or <tt>null</tt> |
| 84 | * is no service is available. |
| 85 | **/ |
| 86 | private ContentHandler getContentHandlerService() |
| 87 | { |
| 88 | // Get the framework instance associated with call stack. |
| 89 | Felix framework = URLHandlers.getFrameworkFromContext(); |
| 90 | |
| 91 | // If the framework has disabled the URL Handlers service, |
| 92 | // then it will not be found so just return null. |
| 93 | if (framework == null) |
| 94 | { |
| 95 | return null; |
| 96 | } |
| 97 | |
| 98 | // Get the service tracker for the framework instance or create one. |
| 99 | URLHandlersServiceTracker tracker = |
| 100 | (URLHandlersServiceTracker) m_trackerMap.get(framework); |
| 101 | if (tracker == null) |
| 102 | { |
| 103 | // Get the framework's system bundle context. |
| 104 | BundleContext context = |
| 105 | ((SystemBundleActivator) |
| 106 | ((SystemBundle) framework.getBundle(0)).getActivator()) |
| 107 | .getBundleContext(); |
| 108 | // Create a filter for the mime type. |
| 109 | String filter = |
| 110 | "(&(objectClass=" |
| 111 | + ContentHandler.class.getName() |
| 112 | + ")(" |
| 113 | + URLConstants.URL_CONTENT_MIMETYPE |
| 114 | + "=" |
| 115 | + m_mimeType |
| 116 | + "))"; |
| 117 | // Create a simple service tracker for the framework. |
| 118 | tracker = new URLHandlersServiceTracker(context, filter); |
| 119 | // Cache the simple service tracker. |
| 120 | m_trackerMap.put(framework, tracker); |
| 121 | } |
| 122 | return (ContentHandler) tracker.getService(); |
| 123 | } |
| 124 | } |