Clarify destruction order effect in @dependsOn annotation javadoc

Issue: SPR-17384

Author: jhoeller

spring-context/src/main/java/org/springframework/context/annotation/DependsOn.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2018 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.
@@ -28,6 +28,12 @@
  * does not explicitly depend on another through properties or constructor arguments,
  * but rather depends on the side effects of another bean's initialization.
  *
+ * <p>A depends-on declaration can specify both an initialization-time dependency and,
+ * in the case of singleton beans only, a corresponding destruction-time dependency.
+ * Dependent beans that define a depends-on relationship with a given bean are destroyed
+ * first, prior to the given bean itself being destroyed. Thus, a depends-on declaration
+ * can also control shutdown order.
+ *
  * <p>May be used on any class directly or indirectly annotated with
  * {@link org.springframework.stereotype.Component} or on methods annotated
  * with {@link Bean}.