OF-1045: Fix NPE in cluster info page

Ensure cluster listener is properly initialized (and destroyed).

src/plugins/hazelcast/src/java/org/jivesoftware/openfire/plugin/util/cache/ClusteredCacheFactory.java

@@ -99,6 +99,8 @@ public class ClusteredCacheFactory implements CacheFactoryStrategy {
     private static HazelcastInstance hazelcast = null;
     private static Cluster cluster = null;
     private ClusterListener clusterListener;
+    private String lifecycleListener;
+    private String membershipListener;
 
     /**
      * Keeps that running state. Initial state is stopped.
@@ -141,8 +143,8 @@ public class ClusteredCacheFactory implements CacheFactoryStrategy {
 	            XMPPServer.getInstance().setNodeID(NodeID.getInstance(getClusterMemberID()));
 	            // CacheFactory is now using clustered caches. We can add our listeners.
 	            clusterListener = new ClusterListener(cluster);
-	            hazelcast.getLifecycleService().addLifecycleListener(clusterListener);
-	            cluster.addMembershipListener(clusterListener);
+	            lifecycleListener = hazelcast.getLifecycleService().addLifecycleListener(clusterListener);
+	            membershipListener = cluster.addMembershipListener(clusterListener);
 	            break;
 	        } catch (Exception e) {
 	            if (retry < CLUSTER_STARTUP_RETRY_COUNT) {
@@ -172,6 +174,7 @@ public class ClusteredCacheFactory implements CacheFactoryStrategy {
         // Stop the cluster
         Hazelcast.shutdownAll();
         cluster = null;
+        if (clusterListener != null) {
 	        // Wait until the server has updated its internal state
 	        while (!clusterListener.isDone()) {
 	            try {
@@ -180,6 +183,12 @@ public class ClusteredCacheFactory implements CacheFactoryStrategy {
 	                // Ignore
 	            }
 	        }
+	        hazelcast.getLifecycleService().removeLifecycleListener(lifecycleListener);
+	        cluster.removeMembershipListener(membershipListener);
+	        lifecycleListener = null;
+	        membershipListener = null;
+	        clusterListener = null;
+        }
         // Reset the node ID
         XMPPServer.getInstance().setNodeID(null);
 
@@ -225,7 +234,7 @@ public class ClusteredCacheFactory implements CacheFactoryStrategy {
     }
 
     public Collection<ClusterNodeInfo> getClusterNodesInfo() {
-    	return clusterListener.getClusterNodesInfo();
+    	return clusterListener == null ? Collections.EMPTY_LIST : clusterListener.getClusterNodesInfo();
     }
 
     public int getMaxClusterNodes() {

src/plugins/hazelcast/src/web/system-clustering-node.jsp

@@ -86,6 +86,7 @@
 	List<ClusterNodeInfo> members = (List<ClusterNodeInfo>) CacheFactory.getClusterNodesInfo();
     Map<NodeID, NodeRuntimeStats.NodeInfo> nodeInfoMap = NodeRuntimeStats.getNodeInfo();
 
+    if (members.size() > 1) {
 	    // Sort it according to name
 	    Collections.sort(members, new Comparator<ClusterNodeInfo>() {
 	        public int compare(ClusterNodeInfo member1, ClusterNodeInfo member2) {
@@ -94,11 +95,12 @@
 	            return name1.toLowerCase().compareTo(name2.toLowerCase().toLowerCase());
 	        }
 	    });
+    }
 
     // If no UID was used, use the UID from the first member in the member list
     byte[] byteArray;
     if (uid == null) {
-        byteArray = members.get(0).getNodeID().toByteArray();
+        byteArray = members.isEmpty() ? new byte[] {0} : members.get(0).getNodeID().toByteArray();
     } else {
         byteArray = Base64.decode(uid, Base64.URL_SAFE);
     }