Change SubscribeExtension's jid field type from String to Jid

and make it final.

smack-extensions/src/main/java/org/jivesoftware/smackx/pubsub/Node.java

@@ -46,6 +46,10 @@ import org.jivesoftware.smackx.shim.packet.Header;
 import org.jivesoftware.smackx.shim.packet.HeadersExtension;
 import org.jivesoftware.smackx.xdata.Form;
 
+import org.jxmpp.jid.Jid;
+import org.jxmpp.jid.impl.JidCreate;
+import org.jxmpp.stringprep.XmppStringprepException;
+
 public abstract class Node {
     protected final PubSubManager pubSubManager;
     protected final String id;
@@ -386,12 +390,45 @@ public abstract class Node {
      * @throws NotConnectedException
      * @throws InterruptedException
      */
-    public Subscription subscribe(String jid) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
+    public Subscription subscribe(Jid jid) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
         PubSub pubSub = createPubsubPacket(Type.set, new SubscribeExtension(jid, getId()));
         PubSub reply = sendPubsubPacket(pubSub);
         return reply.getExtension(PubSubElementType.SUBSCRIPTION);
     }
 
+    /**
+     * The user subscribes to the node using the supplied jid.  The
+     * bare jid portion of this one must match the jid for the connection.
+     *
+     * Please note that the {@link Subscription.State} should be checked
+     * on return since more actions may be required by the caller.
+     * {@link Subscription.State#pending} - The owner must approve the subscription
+     * request before messages will be received.
+     * {@link Subscription.State#unconfigured} - If the {@link Subscription#isConfigRequired()} is true,
+     * the caller must configure the subscription before messages will be received.  If it is false
+     * the caller can configure it but is not required to do so.
+     *
+     * @param jidString The jid to subscribe as.
+     * @return The subscription
+     * @throws XMPPErrorException
+     * @throws NoResponseException
+     * @throws NotConnectedException
+     * @throws InterruptedException
+     * @throws IllegalArgumentException if the provided string is not a valid JID.
+     * @deprecated use {@link #subscribe(Jid)} instead.
+     */
+    @Deprecated
+    // TODO: Remove in Smack 4.5.
+    public Subscription subscribe(String jidString) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
+        Jid jid;
+        try {
+            jid = JidCreate.from(jidString);
+        } catch (XmppStringprepException e) {
+            throw new IllegalArgumentException(e);
+        }
+        return subscribe(jid);
+    }
+
     /**
      * The user subscribes to the node using the supplied jid and subscription
      * options.  The bare jid portion of this one must match the jid for the
@@ -414,13 +451,49 @@ public abstract class Node {
      * @throws NotConnectedException
      * @throws InterruptedException
      */
-    public Subscription subscribe(String jid, SubscribeForm subForm) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
+    public Subscription subscribe(Jid jid, SubscribeForm subForm) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
         PubSub request = createPubsubPacket(Type.set, new SubscribeExtension(jid, getId()));
         request.addExtension(new FormNode(FormNodeType.OPTIONS, subForm));
         PubSub reply = sendPubsubPacket(request);
         return reply.getExtension(PubSubElementType.SUBSCRIPTION);
     }
 
+    /**
+     * The user subscribes to the node using the supplied jid and subscription
+     * options.  The bare jid portion of this one must match the jid for the
+     * connection.
+     *
+     * Please note that the {@link Subscription.State} should be checked
+     * on return since more actions may be required by the caller.
+     * {@link Subscription.State#pending} - The owner must approve the subscription
+     * request before messages will be received.
+     * {@link Subscription.State#unconfigured} - If the {@link Subscription#isConfigRequired()} is true,
+     * the caller must configure the subscription before messages will be received.  If it is false
+     * the caller can configure it but is not required to do so.
+     *
+     * @param jidString The jid to subscribe as.
+     * @param subForm
+     *
+     * @return The subscription
+     * @throws XMPPErrorException
+     * @throws NoResponseException
+     * @throws NotConnectedException
+     * @throws InterruptedException
+     * @throws IllegalArgumentException if the provided string is not a valid JID.
+     * @deprecated use {@link #subscribe(Jid, SubscribeForm)} instead.
+     */
+    @Deprecated
+    // TODO: Remove in Smack 4.5.
+    public Subscription subscribe(String jidString, SubscribeForm subForm) throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
+        Jid jid;
+        try {
+            jid = JidCreate.from(jidString);
+        } catch (XmppStringprepException e) {
+            throw new IllegalArgumentException(e);
+        }
+        return subscribe(jid, subForm);
+    }
+
     /**
      * Remove the subscription related to the specified JID.  This will only
      * work if there is only 1 subscription.  If there are multiple subscriptions,

smack-extensions/src/main/java/org/jivesoftware/smackx/pubsub/SubscribeExtension.java

@@ -16,25 +16,27 @@
  */
 package org.jivesoftware.smackx.pubsub;
 
+import org.jxmpp.jid.Jid;
+
 /**
  * Represents a request to subscribe to a node.
  *
  * @author Robin Collier
  */
 public class SubscribeExtension extends NodeExtension {
-    protected String jid;
+    protected final Jid jid;
 
-    public SubscribeExtension(String subscribeJid) {
+    public SubscribeExtension(Jid subscribeJid) {
         super(PubSubElementType.SUBSCRIBE);
         jid = subscribeJid;
     }
 
-    public SubscribeExtension(String subscribeJid, String nodeId) {
+    public SubscribeExtension(Jid subscribeJid, String nodeId) {
         super(PubSubElementType.SUBSCRIBE, nodeId);
         jid = subscribeJid;
     }
 
-    public String getJid() {
+    public Jid getJid() {
         return jid;
     }