Support for parsing embedded extensions from the server

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@11349 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smackx/provider/EmbeddedExtensionProvider.java

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+/**
+ * All rights reserved. Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jivesoftware.smackx.provider;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.jivesoftware.smack.packet.PacketExtension;
+import org.jivesoftware.smack.provider.PacketExtensionProvider;
+import org.jivesoftware.smack.util.PacketParserUtils;
+import org.jivesoftware.smackx.pubsub.provider.ItemProvider;
+import org.jivesoftware.smackx.pubsub.provider.ItemsProvider;
+import org.xmlpull.v1.XmlPullParser;
+
+/**
+ * 
+ * This class simplifies parsing of embedded elements by using the 
+ * <a href="http://en.wikipedia.org/wiki/Template_method_pattern">Template Method Pattern</a>.  
+ * After extracting the current element attributes and content of any child elements, the template method 
+ * ({@link #createReturnExtension(String, String, Map, List)} is called.  Subclasses
+ * then override this method to create the specific return type.
+ * 
+ * <p>To use this class, you simply register your subclasses as extension providers in the 
+ * <b>smack.properties</b> file.  Then they will be automatically picked up and used to parse
+ * any child elements.  
+ * 
+ * <pre>
+ * For example, given the following message
+ * 
+ * &lt;message from='pubsub.shakespeare.lit' to='francisco@denmark.lit' id='foo&gt;
+ *    &lt;event xmlns='http://jabber.org/protocol/pubsub#event&gt;
+ *       &lt;items node='princely_musings'&gt;
+ *          &lt;item id='asdjkwei3i34234n356'&gt;
+ *             &lt;entry xmlns='http://www.w3.org/2005/Atom'&gt;
+ *                &lt;title&gt;Soliloquy&lt;/title&gt;
+ *                &lt;link rel='alternative' type='text/html'/&gt;
+ *                &lt;id>tag:denmark.lit,2003:entry-32397&lt;/id&gt;
+ *             &lt;/entry&gt;
+ *          &lt;/item&gt;
+ *       &lt;/items&gt;
+ *    &lt;/event&gt;
+ * &lt;/message&gt;
+ * 
+ * I would have a classes
+ * {@link ItemsProvider} extends {@link EmbeddedExtensionProvider}
+ * {@link ItemProvider} extends {@link EmbeddedExtensionProvider}
+ * and
+ * AtomProvider extends {@link PacketExtensionProvider}
+ * 
+ * These classes are then registered in the meta-inf/smack.providers file
+ * as follows.
+ * 
+ *   &lt;extensionProvider&gt;
+ *      &lt;elementName&gt;items&lt;/elementName&gt;
+ *      &lt;namespace&gt;http://jabber.org/protocol/pubsub#event&lt;/namespace&gt;
+ *      &lt;className&gt;org.jivesoftware.smackx.provider.ItemsEventProvider&lt;/className&gt;
+ *   &lt;/extensionProvider&gt;
+ *   &lt;extensionProvider&gt;
+ *       &lt;elementName&gt;item&lt;/elementName&gt;
+ *       &lt;namespace&gt;http://jabber.org/protocol/pubsub#event&lt;/namespace&gt;
+ *       &lt;className&gt;org.jivesoftware.smackx.provider.ItemProvider&lt;/className&gt;
+ *   &lt;/extensionProvider&gt;
+ * 
+ * </pre>
+ * 
+ * @author Robin Collier
+ */
+abstract public class EmbeddedExtensionProvider implements PacketExtensionProvider
+{
+
+	final public PacketExtension parseExtension(XmlPullParser parser) throws Exception
+	{
+        String namespace = parser.getNamespace();
+        String name = parser.getName();
+        Map<String, String> attMap = new HashMap<String, String>();
+        
+        for(int i=0; i<parser.getAttributeCount(); i++)
+        {
+        	attMap.put(parser.getAttributeName(i), parser.getAttributeValue(i));
+        }
+        List<PacketExtension> extensions = new ArrayList<PacketExtension>();
+        
+        do
+        {
+            int tag = parser.next();
+
+            if (tag == XmlPullParser.START_TAG) 
+            	extensions.add(PacketParserUtils.parsePacketExtension(parser.getName(), parser.getNamespace(), parser));
+        } while (!name.equals(parser.getName()));
+
+		return createReturnExtension(name, namespace, attMap, extensions);
+	}
+
+	abstract protected PacketExtension createReturnExtension(String currentElement, String currentNamespace, Map<String, String> attributeMap, List<? extends PacketExtension> content);
+}