Avoid filtering if selector header is not in use

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/AbstractSubscriptionRegistry.java

@@ -23,6 +23,8 @@ import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHeaders;
 import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
 import org.springframework.messaging.simp.SimpMessageType;
+import org.springframework.util.CollectionUtils;
+import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
 /**
@@ -35,6 +37,10 @@ import org.springframework.util.MultiValueMap;
  */
 public abstract class AbstractSubscriptionRegistry implements SubscriptionRegistry {
 
+	private static MultiValueMap<String, String> EMPTY_MAP =
+			CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<String, String>(0));
+
+
 	protected final Log logger = LogFactory.getLog(getClass());
 
 
@@ -104,7 +110,7 @@ public abstract class AbstractSubscriptionRegistry implements SubscriptionRegist
 		String destination = SimpMessageHeaderAccessor.getDestination(headers);
 		if (destination == null) {
 			logger.error("No destination in " + message);
-			return null;
+			return EMPTY_MAP;
 		}
 
 		return findSubscriptionsInternal(destination, message);

spring-messaging/src/main/java/org/springframework/messaging/simp/broker/DefaultSubscriptionRegistry.java

@@ -72,7 +72,9 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 
 	private String selectorHeaderName = "selector";
 
-	private ExpressionParser expressionParser = new SpelExpressionParser();
+	private volatile boolean selectorHeaderInUse = false;
+
+	private final ExpressionParser expressionParser = new SpelExpressionParser();
 
 	private final DestinationCache destinationCache = new DestinationCache();
 
@@ -143,6 +145,7 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 		if (selector != null) {
 			try {
 				expression = this.expressionParser.parseExpression(selector);
+				this.selectorHeaderInUse = true;
 				if (logger.isTraceEnabled()) {
 					logger.trace("Subscription selector: [" + selector + "]");
 				}
@@ -185,6 +188,9 @@ public class DefaultSubscriptionRegistry extends AbstractSubscriptionRegistry {
 	private MultiValueMap<String, String> filterSubscriptions(
 			MultiValueMap<String, String> allMatches, Message<?> message) {
 
+		if (!this.selectorHeaderInUse) {
+			return allMatches;
+		}
 		EvaluationContext context = null;
 		MultiValueMap<String, String> result = new LinkedMultiValueMap<String, String>(allMatches.size());
 		for (String sessionId : allMatches.keySet()) {