Explicit notes on class/method-level semantics in class hierarchies

Issue: SPR-17445

spring-tx/src/main/java/org/springframework/transaction/annotation/Transactional.java

@@ -27,7 +27,12 @@ import org.springframework.core.annotation.AliasFor;
 import org.springframework.transaction.TransactionDefinition;
 
 /**
- * Describes transaction attributes on a method or class.
+ * Describes a transaction attribute on an individual method or on a class.
+ *
+ * <p>At the class level, this annotation applies as a default to all methods of
+ * the declaring class and its subclasses. Note that it does not apply to ancestor
+ * classes up the class hierarchy; methods need to be locally redeclared in order
+ * to participate in a subclass-level annotation.
  *
  * <p>This annotation type is generally directly comparable to Spring's
  * {@link org.springframework.transaction.interceptor.RuleBasedTransactionAttribute}