OF-821: Prevent duplicates for MUC item query

Corrects issue with multiple JIDs sharing a nickname (masquerading)

src/java/org/jivesoftware/openfire/disco/DiscoItem.java

@@ -42,6 +42,8 @@ public class DiscoItem implements Result {
 	private final String node;
 	private final String action;
     private final Element element;
+    
+    private volatile String uid = null;
 
     public DiscoItem(Element element) {
         this.element = element;
@@ -169,17 +171,39 @@ public class DiscoItem implements Result {
 	 */
 	@Override
 	public String getUID() {
-		final StringBuilder sb = new StringBuilder(jid.toString());
-		if (name != null) {
-			sb.append(name);
-		}
-		if (node != null) {
-			sb.append(node);
-		}
-		if (action != null) {
-			sb.append(action);
+		if (uid == null) {
+			synchronized(this) {
+				if (uid == null) {
+					final StringBuilder sb = new StringBuilder(jid.toString());
+					if (name != null) {
+						sb.append(name);
+					}
+					if (node != null) {
+						sb.append(node);
+					}
+					if (action != null) {
+						sb.append(action);
+					}
+					uid = sb.toString();
+				}
+			}
 		}
+		return uid;
+	}
+
+	@Override
+	public int hashCode() {
+		return getUID().hashCode();
+	}
 
-		return sb.toString();
+	@Override
+	public boolean equals(Object obj) {
+		return obj instanceof DiscoItem && getUID().equals(((DiscoItem)obj).getUID());
+	}
+
+	@Override
+	public String toString() {
+		return element == null ? null : element.asXML();
 	}
+	
 }
\ No newline at end of file

src/java/org/jivesoftware/openfire/muc/spi/MultiUserChatServiceImpl.java

@@ -24,12 +24,18 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.Date;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Queue;
+import java.util.Set;
 import java.util.TimerTask;
-import java.util.concurrent.*;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.LinkedBlockingQueue;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.concurrent.atomic.AtomicLong;
 
@@ -60,7 +66,11 @@ import org.jivesoftware.openfire.muc.cluster.GetNumberConnectedUsers;
 import org.jivesoftware.openfire.muc.cluster.OccupantAddedEvent;
 import org.jivesoftware.openfire.muc.cluster.RoomAvailableEvent;
 import org.jivesoftware.openfire.muc.cluster.RoomRemovedEvent;
-import org.jivesoftware.util.*;
+import org.jivesoftware.util.JiveGlobals;
+import org.jivesoftware.util.JiveProperties;
+import org.jivesoftware.util.LocaleUtils;
+import org.jivesoftware.util.TaskEngine;
+import org.jivesoftware.util.XMPPDateTimeFormat;
 import org.jivesoftware.util.cache.CacheFactory;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -1636,7 +1646,7 @@ public class MultiUserChatServiceImpl implements Component, MultiUserChatService
         if (!isServiceEnabled()) {
             return null;
         }
-        List<DiscoItem> answer = new ArrayList<>();
+        Set<DiscoItem> answer = new HashSet<>();
 		if (name == null && node == null)
 		{
 			// Answer all the public rooms as items