Clarified repeatable PropertySource annotation vs use as meta-annotation

Issue: SPR-16592

(cherry picked from commit c4e9ce8)

Author: jhoeller

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 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.
@@ -287,18 +287,23 @@ static Set<AnnotationAttributes> attributesForRepeatable(AnnotationMetadata meta
 	}
 
 	@SuppressWarnings("unchecked")
-	static Set<AnnotationAttributes> attributesForRepeatable(AnnotationMetadata metadata,
-			String containerClassName, String annotationClassName) {
+	static Set<AnnotationAttributes> attributesForRepeatable(
+			AnnotationMetadata metadata, String containerClassName, String annotationClassName) {
 
 		Set<AnnotationAttributes> result = new LinkedHashSet<AnnotationAttributes>();
+
+		// Direct annotation present?
 		addAttributesIfNotNull(result, metadata.getAnnotationAttributes(annotationClassName, false));
 
+		// Container annotation present?
 		Map<String, Object> container = metadata.getAnnotationAttributes(containerClassName, false);
 		if (container != null && container.containsKey("value")) {
 			for (Map<String, Object> containedAttributes : (Map<String, Object>[]) container.get("value")) {
 				addAttributesIfNotNull(result, containedAttributes);
 			}
 		}
+
+		// Return merged result
 		return Collections.unmodifiableSet(result);
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 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.
@@ -42,6 +42,7 @@
  * @Configuration
  * @PropertySource("classpath:/com/myco/app.properties")
  * public class AppConfig {
+ *
  *     @Autowired
  *     Environment env;
  *
@@ -53,8 +54,8 @@
  *     }
  * }</pre>
  *
- * Notice that the {@code Environment} object is @{@link
- * org.springframework.beans.factory.annotation.Autowired Autowired} into the
+ * Notice that the {@code Environment} object is
+ * {@link org.springframework.beans.factory.annotation.Autowired @Autowired} into the
  * configuration class and then used when populating the {@code TestBean} object. Given
  * the configuration above, a call to {@code testBean.getName()} will return "myTestBean".
  *
@@ -79,6 +80,7 @@
  * &#064;Configuration
  * &#064;PropertySource("classpath:/com/${my.placeholder:default/path}/app.properties")
  * public class AppConfig {
+ *
  *     &#064;Autowired
  *     Environment env;
  *
@@ -118,9 +120,9 @@
  *
  * The override ordering depends on the order in which these classes are registered
  * with the application context.
+ *
  * <pre class="code">
- * AnnotationConfigApplicationContext ctx =
- *     new AnnotationConfigApplicationContext();
+ * AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext();
  * ctx.register(ConfigA.class);
  * ctx.register(ConfigB.class);
  * ctx.refresh();
@@ -139,6 +141,12 @@
  * and {@link org.springframework.core.env.MutablePropertySources MutablePropertySources}
  * javadocs for details.
  *
+ * <p><b>NOTE: This annotation is repeatable according to Java 8 conventions.</b>
+ * However, all such {@code @PropertySource} annotations need to be declared at the same
+ * level: either directly on the configuration class or as meta-annotations within the
+ * same custom annotation. Mixing of direct annotations and meta-annotations is not
+ * recommended since direct annotations will effectively override meta-annotations.
+ *
  * @author Chris Beams
  * @author Juergen Hoeller
  * @author Phillip Webb