CompositePropertySource extends EnumerablePropertySource now

Issue: SPR-12292

spring-core/src/main/java/org/springframework/core/env/CompositePropertySource.java

@@ -17,21 +17,29 @@
 package org.springframework.core.env;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
 
+import org.springframework.util.StringUtils;
+
 /**
  * Composite {@link PropertySource} implementation that iterates over a set of
  * {@link PropertySource} instances. Necessary in cases where multiple property sources
  * share the same name, e.g. when multiple values are supplied to {@code @PropertySource}.
  *
+ * <p>As of Spring 4.1.2, this class extends {@link EnumerablePropertySource} instead
+ * of plain {@link PropertySource}, exposing {@link #getPropertyNames()} based on the
+ * accumulated property names from all contained sources (as far as possible).
+ *
  * @author Chris Beams
+ * @author Juergen Hoeller
  * @author Phillip Webb
  * @since 3.1.1
  */
-public class CompositePropertySource extends PropertySource<Object> {
+public class CompositePropertySource extends EnumerablePropertySource<Object> {
 
 	private final Set<PropertySource<?>> propertySources = new LinkedHashSet<PropertySource<?>>();
 
@@ -56,6 +64,28 @@ public class CompositePropertySource extends PropertySource<Object> {
 		return null;
 	}
 
+	@Override
+	public boolean containsProperty(String name) {
+		for (PropertySource<?> propertySource : this.propertySources) {
+			if (propertySource.containsProperty(name)) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	@Override
+	public String[] getPropertyNames() {
+		Set<String> names = new LinkedHashSet<String>();
+		for (PropertySource<?> propertySource : this.propertySources) {
+			if (propertySource instanceof EnumerablePropertySource) {
+				names.addAll(Arrays.asList(((EnumerablePropertySource<?>) propertySource).getPropertyNames()));
+			}
+		}
+		return StringUtils.toStringArray(names);
+	}
+
+
 	/**
 	 * Add the given {@link PropertySource} to the end of the chain.
 	 * @param propertySource the PropertySource to add
@@ -84,6 +114,7 @@ public class CompositePropertySource extends PropertySource<Object> {
 		return this.propertySources;
 	}
 
+
 	@Override
 	public String toString() {
 		return String.format("%s [name='%s', propertySources=%s]",

spring-core/src/main/java/org/springframework/core/env/EnumerablePropertySource.java

@@ -47,6 +47,11 @@ public abstract class EnumerablePropertySource<T> extends PropertySource<T> {
 		super(name, source);
 	}
 
+	@SuppressWarnings("unchecked")
+	protected EnumerablePropertySource(String name) {
+		super(name);
+	}
+
 
 	/**
 	 * Return whether this {@code PropertySource} contains a property with the given name.

spring-core/src/main/java/org/springframework/core/env/PropertySource.java

@@ -75,10 +75,10 @@ public abstract class PropertySource<T> {
 	}
 
 	/**
-	 * Create a new {@code PropertySource} with the given name and with a new {@code Object}
-	 * instance as the underlying source.
-	 * <p>Often useful in testing scenarios when creating anonymous implementations that
-	 * never query an actual source but rather return hard-coded values.
+	 * Create a new {@code PropertySource} with the given name and with a new
+	 * {@code Object} instance as the underlying source.
+	 * <p>Often useful in testing scenarios when creating anonymous implementations
+	 * that never query an actual source but rather return hard-coded values.
 	 */
 	@SuppressWarnings("unchecked")
 	public PropertySource(String name) {