YamlPropertiesFactoryBean consistently exposes String values

Issue: SPR-14737
(cherry picked from commit 74c6188)

spring-core/src/main/java/org/springframework/core/CollectionFactory.java

@@ -29,6 +29,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.NavigableMap;
 import java.util.NavigableSet;
+import java.util.Properties;
 import java.util.Set;
 import java.util.SortedMap;
 import java.util.SortedSet;
@@ -40,12 +41,9 @@ import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
 /**
- * Factory for collections that is aware of Java 5, Java 6, and Spring
- * collection types.
+ * Factory for collections that is aware of Java 5, Java 6, and Spring collection types.
+ *
  * <p>Mainly for internal use within the framework.
- * <p>The goal of this class is to avoid runtime dependencies on a specific
- * Java version, while nevertheless using the best collection implementation
- * that is available at runtime.
  *
  * @author Juergen Hoeller
  * @author Arjen Poutsma
@@ -324,6 +322,23 @@ public abstract class CollectionFactory {
 		}
 	}
 
+	/**
+	 * Create a variant of {@code java.util.Properties} that automatically adapts
+	 * non-String values to String representations on {@link Properties#getProperty}.
+	 * @return a new {@code Properties} instance
+	 * @since 4.3.4
+	 */
+	@SuppressWarnings("serial")
+	public static Properties createStringAdaptingProperties() {
+		return new Properties() {
+			@Override
+			public String getProperty(String key) {
+				Object value = get(key);
+				return (value != null ? value.toString() : null);
+			}
+		};
+	}
+
 	/**
 	 * Cast the given type to a subtype of {@link Enum}.
 	 * @param enumType the enum type, never {@code null}

spring-core/src/main/java/org/springframework/util/CollectionUtils.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -110,10 +110,10 @@ public abstract class CollectionUtils {
 		if (props != null) {
 			for (Enumeration<?> en = props.propertyNames(); en.hasMoreElements();) {
 				String key = (String) en.nextElement();
-				Object value = props.getProperty(key);
+				Object value = props.get(key);
 				if (value == null) {
-					// Potentially a non-String value...
-					value = props.get(key);
+					// Allow for defaults fallback or potentially overridden accessor...
+					value = props.getProperty(key);
 				}
 				map.put((K) key, (V) value);
 			}