Add @PropertySources and ignoreResourceNotFound

Support repeatable @PropertySource annotations in Java 8 and add
@PropertySources container annotation for Java 6/7. Also add an
ignoreResourceNotFound attribute to @PropertySource allowing missing
property resources to be silently ignored.

This commit also introduces some generally useful methods to
AnnotationUtils for working with @Repeatable annotations.

Issue: SPR-8371

spring-core/src/main/java/org/springframework/core/annotation/AnnotationUtils.java

@@ -19,12 +19,18 @@ package org.springframework.core.annotation;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.AnnotatedElement;
 import java.lang.reflect.Method;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.WeakHashMap;
 
 import org.springframework.core.BridgeMethodResolver;
 import org.springframework.util.Assert;
+import org.springframework.util.ObjectUtils;
 
 /**
  * General utility methods for working with annotations, handling bridge methods (which the compiler
@@ -43,6 +49,7 @@ import org.springframework.util.Assert;
  * @author Sam Brannen
  * @author Mark Fisher
  * @author Chris Beams
+ * @author Phillip Webb
  * @since 2.0
  * @see java.lang.reflect.Method#getAnnotations()
  * @see java.lang.reflect.Method#getAnnotation(Class)
@@ -117,6 +124,45 @@ public abstract class AnnotationUtils {
 		return getAnnotation((AnnotatedElement) resolvedMethod, annotationType);
 	}
 
+	/**
+	 * Get the possibly repeating {@link Annotation}s of {@code annotationType} from the
+	 * supplied {@link Method}. Deals with both a single direct annotation and repeating
+	 * annotations nested within a containing annotation.
+	 * <p>Correctly handles bridge {@link Method Methods} generated by the compiler.
+	 * @param method the method to look for annotations on
+	 * @param containerAnnotationType the class of the container that holds the annotations
+	 * @param annotationType the annotation class to look for
+	 * @return the annotations found
+	 * @see org.springframework.core.BridgeMethodResolver#findBridgedMethod(Method)
+	 * @since 4.0
+	 */
+	public static <A extends Annotation> Set<A> getRepeatableAnnotation(Method method,
+			Class<? extends Annotation> containerAnnotationType, Class<A> annotationType) {
+		Method resolvedMethod = BridgeMethodResolver.findBridgedMethod(method);
+		return getRepeatableAnnotation((AnnotatedElement) resolvedMethod,
+				containerAnnotationType, annotationType);
+	}
+
+	/**
+	 * Get the possibly repeating {@link Annotation}s of {@code annotationType} from the
+	 * supplied {@link AnnotatedElement}. Deals with both a single direct annotation and
+	 * repeating annotations nested within a containing annotation.
+	 * <p>Correctly handles bridge {@link Method Methods} generated by the compiler.
+	 * @param annotatedElement the element to look for annotations on
+	 * @param containerAnnotationType the class of the container that holds the annotations
+	 * @param annotationType the annotation class to look for
+	 * @return the annotations found
+	 * @see org.springframework.core.BridgeMethodResolver#findBridgedMethod(Method)
+	 * @since 4.0
+	 */
+	public static <A extends Annotation> Set<A> getRepeatableAnnotation(AnnotatedElement annotatedElement,
+			Class<? extends Annotation> containerAnnotationType, Class<A> annotationType) {
+		if (annotatedElement.getAnnotations().length == 0) {
+			return Collections.emptySet();
+		}
+		return new AnnotationCollector<A>(containerAnnotationType, annotationType).getResult(annotatedElement);
+	}
+
 	/**
 	 * Get a single {@link Annotation} of {@code annotationType} from the supplied {@link Method},
 	 * traversing its super methods if no annotation can be found on the given method itself.
@@ -521,4 +567,59 @@ public abstract class AnnotationUtils {
 		}
 	}
 
+
+	private static class AnnotationCollector<A extends Annotation> {
+
+
+		private final Class<? extends Annotation> containerAnnotationType;
+
+		private final Class<A> annotationType;
+
+		private final Set<AnnotatedElement> visited = new HashSet<AnnotatedElement>();
+
+		private final Set<A> result = new LinkedHashSet<A>();
+
+
+		public AnnotationCollector(Class<? extends Annotation> containerAnnotationType,
+				Class<A> annotationType) {
+			this.containerAnnotationType = containerAnnotationType;
+			this.annotationType = annotationType;
+		}
+
+
+		public Set<A> getResult(AnnotatedElement element) {
+			process(element);
+			return Collections.unmodifiableSet(this.result);
+		}
+
+		@SuppressWarnings("unchecked")
+		private void process(AnnotatedElement annotatedElement) {
+			if (this.visited.add(annotatedElement)) {
+				for (Annotation annotation : annotatedElement.getAnnotations()) {
+					if (ObjectUtils.nullSafeEquals(this.annotationType, annotation.annotationType())) {
+						this.result.add((A) annotation);
+					}
+					else if (ObjectUtils.nullSafeEquals(this.containerAnnotationType, annotation.annotationType())) {
+						result.addAll(Arrays.asList(getValue(annotation)));
+					}
+					else {
+						process(annotation.annotationType());
+					}
+				}
+			}
+		}
+
+		@SuppressWarnings("unchecked")
+		private A[] getValue(Annotation annotation) {
+			try {
+				Method method = annotation.annotationType().getDeclaredMethod("value");
+				return (A[]) method.invoke(annotation);
+			}
+			catch (Exception ex) {
+				throw new IllegalStateException("Unable to read value from repeating annotation container "
+								+ this.containerAnnotationType.getName(), ex);
+			}
+		}
+
+	}
 }