Adds an AbstractPacketExtension utility class because I am tired of writing the same stuff over and over again. (Yeah yeah, I should've thought of this earlier). Adds a Crypto packet extension

src/net/java/sip/communicator/impl/protocol/jabber/extensions/AbstractPacketExtension.java

@@ -0,0 +1,135 @@
+/*
+ * SIP Communicator, the OpenSource Java VoIP and Instant Messaging client.
+ *
+ * Distributable under LGPL license.
+ * See terms of license at gnu.org.
+ */
+package net.java.sip.communicator.impl.protocol.jabber.extensions;
+
+import java.util.*;
+
+import org.jivesoftware.smack.packet.*;
+
+/**
+ * A generic implementation of <tt>PacketExtension</tt>. The purpose of this
+ * class is quite similar to that of smack's {@link DefaultPacketExtension}
+ * with the main difference being that this one is meant primarily for
+ * extension rather than using as a fallback for unknown elements. We let for
+ * example our descendants handle child elements and we automate attribute
+ * handling instead.
+ *
+ * @author Emil Ivov
+ */
+public abstract class AbstractPacketExtension
+    implements PacketExtension
+{
+    /**
+     * The name space of this packet extension. Should remain <tt>null</tt> if
+     * there's no namespace associated with this element.
+     */
+    private final String namespace;
+
+    /**
+     * The name space of this packet extension. Should remain <tt>null</tt> if
+     * there's no namespace associated with this element.
+     */
+    private final String elementName;
+
+    /**
+     * A map of all attributes that this extension is currently using.
+     */
+    private final Map<String, Object> attributes
+                                    = new LinkedHashMap<String, Object>();
+
+    /**
+     * Creates an {@link AbstractPacketExtension} instance for the specified
+     * <tt>namespace</tt> and <tt>elementName</tt>.
+     *
+     * @param namespace the XML namespace for this element.
+     * @param elementName the name of the element
+     */
+    protected AbstractPacketExtension(String namespace, String elementName)
+    {
+        this.namespace = namespace;
+        this.elementName = elementName;
+    }
+
+    /**
+     * Returns the name of the <tt>encryption</tt> element.
+     *
+     * @return the name of the <tt>encryption</tt> element.
+     */
+    public String getElementName()
+    {
+        return elementName;
+    }
+
+    /**
+     * Returns the XML namespace for this element or <tt>null</tt> if the
+     * element does not live in a namespace of its own.
+     *
+     * @return the XML namespace for this element or <tt>null</tt> if the
+     * element does not live in a namespace of its own.
+     */
+    public String getNamespace()
+    {
+        return namespace;
+    }
+
+    /**
+     * Returns an XML representation of this extension.
+     *
+     * @return an XML representation of this extension.
+     */
+    public String toXML()
+    {
+        StringBuilder bldr = new StringBuilder("<" + getElementName() + " ");
+
+        if(getNamespace() != null)
+            bldr.append("xmlns='" + getNamespace() + "'");
+
+        //add the rest of the attributes if any
+        for()
+
+        //add child elements if any
+        List<PacketExtension> childElements = getChildElements();
+
+        if(childElements == null || childElements.size() == 0)
+            bldr.append("/>");
+        else
+        {
+            for(PacketExtension packExt : childElements)
+            {
+                bldr.append(packExt.toXML());
+            }
+
+            bldr.append("</"+getElementName()+">");
+        }
+
+        return bldr.toString();
+    }
+
+    /**
+     * Returns all sub-elements for this <tt>AbstractPacketExtension</tt> or
+     * <tt>null</tt> if there aren't any.
+     *
+     * @return the {@link List} of elements that this packet extension contains.
+     */
+    public abstract List<PacketExtension> getChildElements();
+
+    /**
+     * Sets the value of the attribute named <tt>name</tt> to <tt>value</tt>.
+     *
+     * @param name the name of the attribute that we are setting.
+     * @param value an {@link Object} whose <tt>toString()</tt> method returns
+     * the XML value of the attribute we are setting.
+     */
+    protected void setAttribtue(String name, Object value)
+    {
+        synchronized(attributes)
+        {
+            this.attributes.put(name, value);
+        }
+    }
+
+}

src/net/java/sip/communicator/impl/protocol/jabber/extensions/jingle/CryptoPacketExtension.java

@@ -0,0 +1,66 @@
+/*
+ * SIP Communicator, the OpenSource Java VoIP and Instant Messaging client.
+ *
+ * Distributable under LGPL license.
+ * See terms of license at gnu.org.
+ */
+package net.java.sip.communicator.impl.protocol.jabber.extensions.jingle;
+
+import org.jivesoftware.smack.packet.*;
+
+/**
+ * The element containing details about an encryption algorithm that could be
+ * used during a jingle session.
+ *
+ * @author Emil Ivov
+ */
+public class CryptoPacketExtension
+    implements PacketExtension
+{
+    /**
+     * There's no namespace for the <tt>crypto</tt> element itself.
+     */
+    public static final String NAMESPACE = null;
+
+    /**
+     * The name of the "crypto" element.
+     */
+    public static final String ELEMENT_NAME = "crypto";
+
+    /**
+     * Returns the name of the <tt>encryption</tt> element.
+     *
+     * @return the name of the <tt>encryption</tt> element.
+     */
+    public String getElementName()
+    {
+        return ELEMENT_NAME;
+    }
+
+    /**
+     * Returns <tt>null</tt> since there's no encryption specific ns.
+     *
+     * @return <tt>null</tt> since there's no encryption specific ns.
+     */
+    public String getNamespace()
+    {
+        return NAMESPACE;
+    }
+
+    /**
+     * Returns the XML representation of this <tt>description</tt> packet
+     * extension including all child elements.
+     *
+     * @return this packet extension as an XML <tt>String</tt>.
+     */
+    public String toXML()
+    {
+        StringBuilder bldr = new StringBuilder(
+            "<" + ELEMENT_NAME+ " ");
+
+
+        bldr.append("</" + ELEMENT_NAME + ">");
+        return bldr.toString();
+    }
+
+}

src/net/java/sip/communicator/impl/protocol/jabber/extensions/jingle/EncryptionPacketExtension.java

@@ -22,7 +22,7 @@ public class EncryptionPacketExtension
     /**
      * There's no namespace for the <tt>encryption</tt> element itself.
      */
-    public static final String NAMESPACE = "";
+    public static final String NAMESPACE = null;
 
     /**
      * The name of the "encryption" element.