Check hasNext when when accessing sessionIds from UserDestinationResult

spring-messaging/src/main/java/org/springframework/messaging/simp/user/UserDestinationMessageHandler.java

@@ -20,7 +20,6 @@
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
 import org.apache.commons.logging.Log;
@@ -276,11 +275,10 @@ public MessageSendingOperations<String> getMessagingTemplate() {
 		}
 
 		public void send(UserDestinationResult destinationResult, Message<?> message) throws MessagingException {
-			Set<String> sessionIds = destinationResult.getSessionIds();
-			Iterator<String> itr = (sessionIds != null ? sessionIds.iterator() : null);
+			Iterator<String> itr = destinationResult.getSessionIds().iterator();
 
 			for (String target : destinationResult.getTargetDestinations()) {
-				String sessionId = (itr != null ? itr.next() : null);
+				String sessionId = (itr != null && itr.hasNext() ? itr.next() : null);
 				getTemplateToUse(sessionId).send(target, message);
 			}
 		}

spring-messaging/src/main/java/org/springframework/messaging/simp/user/UserDestinationResult.java

@@ -113,7 +113,7 @@ public String getSubscribeDestination() {
 	/**
 	 * Return the session id for the targetDestination.
 	 */
-	public @Nullable Set<String> getSessionIds() {
+	public Set<String> getSessionIds() {
 		return this.sessionIds;
 	}
 

spring-messaging/src/test/java/org/springframework/messaging/simp/user/UserDestinationMessageHandlerTests.java

@@ -17,6 +17,7 @@
 package org.springframework.messaging.simp.user;
 
 import java.nio.charset.StandardCharsets;
+import java.util.Set;
 
 import org.jspecify.annotations.Nullable;
 import org.junit.jupiter.api.Test;
@@ -98,6 +99,26 @@ void handleMessage() {
 		assertThat(accessor.getFirstNativeHeader(ORIGINAL_DESTINATION)).isEqualTo("/user/queue/foo");
 	}
 
+	@Test
+	@SuppressWarnings("rawtypes")
+	void handleMessageWithoutSessionIds() {
+		UserDestinationResolver resolver = mock();
+		Message message = createWith(SimpMessageType.MESSAGE, "joe", null, "/user/joe/queue/foo");
+		UserDestinationResult result = new UserDestinationResult("/queue/foo-user123", Set.of("/queue/foo-user123"), "/user/queue/foo", "joe");
+		given(resolver.resolveDestination(message)).willReturn(result);
+
+		given(this.brokerChannel.send(Mockito.any(Message.class))).willReturn(true);
+		UserDestinationMessageHandler handler = new UserDestinationMessageHandler(new StubMessageChannel(), this.brokerChannel, resolver);
+		handler.handleMessage(message);
+
+		ArgumentCaptor<Message> captor = ArgumentCaptor.forClass(Message.class);
+		Mockito.verify(this.brokerChannel).send(captor.capture());
+
+		SimpMessageHeaderAccessor accessor = SimpMessageHeaderAccessor.wrap(captor.getValue());
+		assertThat(accessor.getDestination()).isEqualTo("/queue/foo-user123");
+		assertThat(accessor.getFirstNativeHeader(ORIGINAL_DESTINATION)).isEqualTo("/user/queue/foo");
+	}
+
 	@Test
 	@SuppressWarnings("rawtypes")
 	void handleMessageWithoutActiveSession() {