Expose current cached session count

Closes gh-26811

spring-jms/src/main/java/org/springframework/jms/connection/CachingConnectionFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -179,6 +179,23 @@ public class CachingConnectionFactory extends SingleConnectionFactory {
 	}
 
 
+	/**
+	 * Return a current session count, indicating the number of sessions currently
+	 * cached by this connection factory.
+	 * @since 5.3.7
+	 */
+	public int getCachedSessionCount() {
+		int count = 0;
+		synchronized (this.cachedSessions) {
+			for (Deque<Session> sessionList : this.cachedSessions.values()) {
+				synchronized (sessionList) {
+					count += sessionList.size();
+				}
+			}
+		}
+		return count;
+	}
+
 	/**
 	 * Resets the Session cache as well.
 	 */