Split ConfigurationPropertySource for iteration

Create separate `IterableConfigurationPropertySource` and
`ConfigurationPropertySource` interfaces so that it's possible to
work out if a source can truly iterate the values that it contains.

Prior to this commit there was only a single
`ConfigurationPropertySource` interface, which returned an empty
Iterator when values could not be iterated. This design made it
impossible to tell the difference between a source that was empty, and
a source that could not be iterated.

The `ConfigurationPropertySources` class has been updated to adapt
non-enumerable and enumerable Spring PropertySources to the correct
`ConfigurationPropertySource` interface. It also deals with the edge
case of the `SystemPropertySource` running in a security restricted
environment.

Fixes gh-9057

spring-boot/src/main/java/org/springframework/boot/context/properties/bind/Binder.java

@@ -36,6 +36,7 @@ import org.springframework.boot.context.properties.source.ConfigurationProperty;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySources;
+import org.springframework.boot.context.properties.source.IterableConfigurationPropertySource;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.env.ConfigurableEnvironment;
 import org.springframework.core.env.Environment;
@@ -288,9 +289,7 @@ public class Binder {
 
 	private Object bindBean(ConfigurationPropertyName name, Bindable<?> target,
 			BindHandler handler, Context context) {
-		boolean hasKnownBindableProperties = context.streamSources()
-				.flatMap((s) -> s.filter(name::isAncestorOf).stream()).findAny()
-				.isPresent();
+		boolean hasKnownBindableProperties = hasKnownBindableProperties(name, context);
 		if (!hasKnownBindableProperties && isUnbindableBean(target)) {
 			return null;
 		}
@@ -307,6 +306,15 @@ public class Binder {
 		});
 	}
 
+	private boolean hasKnownBindableProperties(ConfigurationPropertyName name,
+			Context context) {
+		Stream<IterableConfigurationPropertySource> sources = context.streamSources()
+				.filter(IterableConfigurationPropertySource.class::isInstance)
+				.map(IterableConfigurationPropertySource.class::cast);
+		return sources.flatMap((s) -> s.filter(name::isAncestorOf).stream()).findAny()
+				.isPresent();
+	}
+
 	private boolean isUnbindableBean(Bindable<?> target) {
 		Class<?> resolved = target.getType().resolve();
 		if (resolved.isPrimitive() || NON_BEAN_CLASSES.contains(resolved)) {

spring-boot/src/main/java/org/springframework/boot/context/properties/bind/IndexedElementsBinder.java

@@ -27,6 +27,7 @@ import org.springframework.boot.context.properties.source.ConfigurationProperty;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName.Form;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
+import org.springframework.boot.context.properties.source.IterableConfigurationPropertySource;
 import org.springframework.core.ResolvableType;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -94,7 +95,11 @@ abstract class IndexedElementsBinder<T> extends AggregateBinder<T> {
 	private MultiValueMap<String, ConfigurationProperty> getKnownIndexedChildren(
 			ConfigurationPropertySource source, ConfigurationPropertyName root) {
 		MultiValueMap<String, ConfigurationProperty> children = new LinkedMultiValueMap<>();
-		for (ConfigurationPropertyName name : source.filter(root::isAncestorOf)) {
+		if (!(source instanceof IterableConfigurationPropertySource)) {
+			return children;
+		}
+		for (ConfigurationPropertyName name : (IterableConfigurationPropertySource) source
+				.filter(root::isAncestorOf)) {
 			name = rollUp(name, root);
 			if (name.getElement().isIndexed()) {
 				String key = name.getElement().getValue(Form.UNIFORM);

spring-boot/src/main/java/org/springframework/boot/context/properties/bind/MapBinder.java

@@ -25,6 +25,7 @@ import org.springframework.boot.context.properties.source.ConfigurationProperty;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName.Form;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
+import org.springframework.boot.context.properties.source.IterableConfigurationPropertySource;
 import org.springframework.core.CollectionFactory;
 import org.springframework.core.ResolvableType;
 
@@ -83,13 +84,15 @@ class MapBinder extends AggregateBinder<Map<Object, Object>> {
 
 		public void bindEntries(ConfigurationPropertySource source,
 				Map<Object, Object> map) {
-			for (ConfigurationPropertyName name : source) {
-				Bindable<?> valueBindable = getValueBindable(name);
-				ConfigurationPropertyName entryName = getEntryName(source, name);
-				Object key = getContext().getConversionService()
-						.convert(getKeyName(entryName), this.keyType);
-				Object value = this.elementBinder.bind(entryName, valueBindable);
-				map.putIfAbsent(key, value);
+			if (source instanceof IterableConfigurationPropertySource) {
+				for (ConfigurationPropertyName name : (IterableConfigurationPropertySource) source) {
+					Bindable<?> valueBindable = getValueBindable(name);
+					ConfigurationPropertyName entryName = getEntryName(source, name);
+					Object key = getContext().getConversionService()
+							.convert(getKeyName(entryName), this.keyType);
+					Object value = this.elementBinder.bind(entryName, valueBindable);
+					map.putIfAbsent(key, value);
+				}
 			}
 		}
 

spring-boot/src/main/java/org/springframework/boot/context/properties/bind/handler/NoUnboundElementsBindHandler.java

@@ -28,6 +28,7 @@ import org.springframework.boot.context.properties.bind.UnboundConfigurationProp
 import org.springframework.boot.context.properties.source.ConfigurationProperty;
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
+import org.springframework.boot.context.properties.source.IterableConfigurationPropertySource;
 
 /**
  * {@link BindHandler} to enforce that all configuration properties under the root name
@@ -68,14 +69,9 @@ public class NoUnboundElementsBindHandler extends AbstractBindHandler {
 			BindContext context) {
 		Set<ConfigurationProperty> unbound = new TreeSet<>();
 		for (ConfigurationPropertySource source : context.getSources()) {
-			ConfigurationPropertySource filtered = source
-					.filter((candidate) -> isUnbound(name, candidate));
-			for (ConfigurationPropertyName unboundName : filtered) {
-				try {
-					unbound.add(filtered.getConfigurationProperty(unboundName));
-				}
-				catch (Exception ex) {
-				}
+			if (source instanceof IterableConfigurationPropertySource) {
+				collectUnbound(name, unbound,
+						(IterableConfigurationPropertySource) source);
 			}
 		}
 		if (!unbound.isEmpty()) {
@@ -83,6 +79,21 @@ public class NoUnboundElementsBindHandler extends AbstractBindHandler {
 		}
 	}
 
+	private void collectUnbound(ConfigurationPropertyName name,
+			Set<ConfigurationProperty> unbound,
+			IterableConfigurationPropertySource source) {
+		IterableConfigurationPropertySource filtered = source
+				.filter((candidate) -> isUnbound(name, candidate));
+		for (ConfigurationPropertyName unboundName : filtered) {
+			try {
+				unbound.add(source.filter((candidate) -> isUnbound(name, candidate))
+						.getConfigurationProperty(unboundName));
+			}
+			catch (Exception ex) {
+			}
+		}
+	}
+
 	private boolean isUnbound(ConfigurationPropertyName name,
 			ConfigurationPropertyName candidate) {
 		return name.isAncestorOf(candidate) && !this.boundNames.contains(candidate);

spring-boot/src/main/java/org/springframework/boot/context/properties/source/AliasedConfigurationPropertySource.java

@@ -16,12 +16,7 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.List;
-import java.util.stream.Stream;
-import java.util.stream.StreamSupport;
-
 import org.springframework.util.Assert;
-import org.springframework.util.CollectionUtils;
 
 /**
  * A {@link ConfigurationPropertySource} supporting name aliases.
@@ -43,31 +38,24 @@ class AliasedConfigurationPropertySource implements ConfigurationPropertySource
 		this.aliases = aliases;
 	}
 
-	@Override
-	public Stream<ConfigurationPropertyName> stream() {
-		return StreamSupport.stream(this.source.spliterator(), false)
-				.flatMap(this::addAliases);
-	}
-
-	private Stream<ConfigurationPropertyName> addAliases(ConfigurationPropertyName name) {
-		Stream<ConfigurationPropertyName> names = Stream.of(name);
-		List<ConfigurationPropertyName> aliases = this.aliases.getAliases(name);
-		if (CollectionUtils.isEmpty(aliases)) {
-			return names;
-		}
-		return Stream.concat(names, aliases.stream());
-	}
-
 	@Override
 	public ConfigurationProperty getConfigurationProperty(
 			ConfigurationPropertyName name) {
 		Assert.notNull(name, "Name must not be null");
-		ConfigurationProperty result = this.source.getConfigurationProperty(name);
+		ConfigurationProperty result = getSource().getConfigurationProperty(name);
 		if (result == null) {
-			ConfigurationPropertyName aliasedName = this.aliases.getNameForAlias(name);
-			result = this.source.getConfigurationProperty(aliasedName);
+			ConfigurationPropertyName aliasedName = getAliases().getNameForAlias(name);
+			result = getSource().getConfigurationProperty(aliasedName);
 		}
 		return result;
 	}
 
+	protected ConfigurationPropertySource getSource() {
+		return this.source;
+	}
+
+	protected ConfigurationPropertyNameAliases getAliases() {
+		return this.aliases;
+	}
+
 }

spring-boot/src/main/java/org/springframework/boot/context/properties/source/AliasedIterableConfigurationPropertySource.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import java.util.List;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+import org.springframework.util.CollectionUtils;
+
+/**
+ * A {@link IterableConfigurationPropertySource} supporting name aliases.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ */
+class AliasedIterableConfigurationPropertySource
+		extends AliasedConfigurationPropertySource
+		implements IterableConfigurationPropertySource {
+
+	AliasedIterableConfigurationPropertySource(IterableConfigurationPropertySource source,
+			ConfigurationPropertyNameAliases aliases) {
+		super(source, aliases);
+	}
+
+	@Override
+	public Stream<ConfigurationPropertyName> stream() {
+		return StreamSupport.stream(getSource().spliterator(), false)
+				.flatMap(this::addAliases);
+	}
+
+	private Stream<ConfigurationPropertyName> addAliases(ConfigurationPropertyName name) {
+		Stream<ConfigurationPropertyName> names = Stream.of(name);
+		List<ConfigurationPropertyName> aliases = getAliases().getAliases(name);
+		if (CollectionUtils.isEmpty(aliases)) {
+			return names;
+		}
+		return Stream.concat(names, aliases.stream());
+	}
+
+	@Override
+	protected IterableConfigurationPropertySource getSource() {
+		return (IterableConfigurationPropertySource) super.getSource();
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertySource.java

@@ -16,16 +16,12 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.Iterator;
 import java.util.function.Predicate;
-import java.util.stream.Stream;
 
 import org.springframework.boot.origin.OriginTrackedValue;
-import org.springframework.core.env.PropertySource;
 
 /**
- * A source of {@link ConfigurationProperty ConfigurationProperties}, usually backed by a
- * Spring {@link PropertySource}.
+ * A source of {@link ConfigurationProperty ConfigurationProperties}.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
@@ -34,7 +30,7 @@ import org.springframework.core.env.PropertySource;
  * @see OriginTrackedValue
  * @see #getConfigurationProperty(ConfigurationPropertyName)
  */
-public interface ConfigurationPropertySource extends Iterable<ConfigurationPropertyName> {
+public interface ConfigurationPropertySource {
 
 	/**
 	 * Return a single {@link ConfigurationProperty} from the source or {@code null} if no
@@ -44,29 +40,10 @@ public interface ConfigurationPropertySource extends Iterable<ConfigurationPrope
 	 */
 	ConfigurationProperty getConfigurationProperty(ConfigurationPropertyName name);
 
-	/**
-	 * Return an iterator for the {@link ConfigurationPropertyName names} managed by this
-	 * source. If it is not possible to determine the names an empty iterator may be
-	 * returned.
-	 * @return an iterator (never {@code null})
-	 */
-	@Override
-	default Iterator<ConfigurationPropertyName> iterator() {
-		return stream().iterator();
-	}
-
-	/**
-	 * Returns a sequential {@code Stream} for the {@link ConfigurationPropertyName names}
-	 * managed by this source. If it is not possible to determine the names an
-	 * {@link Stream#empty() empty stream} may be returned.
-	 * @return a stream of names (never {@code null})
-	 */
-	Stream<ConfigurationPropertyName> stream();
-
 	/**
 	 * Return a filtered variant of this source, containing only names that match the
 	 * given {@link Predicate}.
-	 * @param filter the filter to apply
+	 * @param filter the filter to match
 	 * @return a filtered {@link ConfigurationPropertySource} instance
 	 */
 	default ConfigurationPropertySource filter(

spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertySources.java

@@ -24,6 +24,7 @@ import java.util.stream.Stream;
 import java.util.stream.StreamSupport;
 
 import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.EnumerablePropertySource;
 import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertySource;
 import org.springframework.core.env.PropertySources;
@@ -82,10 +83,16 @@ public class ConfigurationPropertySources
 	}
 
 	private ConfigurationPropertySource adapt(PropertySource<?> source) {
-		return this.adapters.computeIfAbsent(source, (k) -> {
-			return new PropertySourceConfigurationPropertySource(source,
-					getPropertyMapper(source));
-		});
+		return this.adapters.computeIfAbsent(source, this::createAdapter);
+	}
+
+	private ConfigurationPropertySource createAdapter(PropertySource<?> source) {
+		PropertyMapper mapper = getPropertyMapper(source);
+		if (isFullEnumerable(source)) {
+			return new PropertySourceIterableConfigurationPropertySource(
+					(EnumerablePropertySource<?>) source, mapper);
+		}
+		return new PropertySourceConfigurationPropertySource(source, mapper);
 	}
 
 	private PropertyMapper getPropertyMapper(PropertySource<?> source) {
@@ -95,6 +102,28 @@ public class ConfigurationPropertySources
 		return DefaultPropertyMapper.INSTANCE;
 	}
 
+	private boolean isFullEnumerable(PropertySource<?> source) {
+		PropertySource<?> rootSource = getRootSource(source);
+		if (rootSource.getSource() instanceof Map) {
+			// Check we're not security restricted
+			try {
+				((Map<?, ?>) rootSource.getSource()).size();
+			}
+			catch (UnsupportedOperationException ex) {
+				return false;
+			}
+		}
+		return (source instanceof EnumerablePropertySource);
+	}
+
+	private PropertySource<?> getRootSource(PropertySource<?> source) {
+		while (source.getSource() != null
+				&& source.getSource() instanceof PropertySource) {
+			source = (PropertySource<?>) source.getSource();
+		}
+		return source;
+	}
+
 	/**
 	 * Attach a {@link ConfigurationPropertySources} instance to the specified
 	 * {@link ConfigurableEnvironment} so that classic

spring-boot/src/main/java/org/springframework/boot/context/properties/source/FilteredConfigurationPropertiesSource.java

@@ -17,8 +17,6 @@
 package org.springframework.boot.context.properties.source;
 
 import java.util.function.Predicate;
-import java.util.stream.Stream;
-import java.util.stream.StreamSupport;
 
 import org.springframework.util.Assert;
 
@@ -42,16 +40,19 @@ class FilteredConfigurationPropertiesSource implements ConfigurationPropertySour
 		this.filter = filter;
 	}
 
-	@Override
-	public Stream<ConfigurationPropertyName> stream() {
-		return StreamSupport.stream(this.source.spliterator(), false).filter(this.filter);
-	}
-
 	@Override
 	public ConfigurationProperty getConfigurationProperty(
 			ConfigurationPropertyName name) {
-		return (this.filter.test(name) ? this.source.getConfigurationProperty(name)
-				: null);
+		boolean filtered = getFilter().test(name);
+		return (filtered ? getSource().getConfigurationProperty(name) : null);
+	}
+
+	protected ConfigurationPropertySource getSource() {
+		return this.source;
+	}
+
+	protected Predicate<ConfigurationPropertyName> getFilter() {
+		return this.filter;
 	}
 
 }

spring-boot/src/main/java/org/springframework/boot/context/properties/source/FilteredIterableConfigurationPropertiesSource.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+import java.util.stream.StreamSupport;
+
+/**
+ * A filtered {@link IterableConfigurationPropertySource}.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ */
+class FilteredIterableConfigurationPropertiesSource
+		extends FilteredConfigurationPropertiesSource
+		implements IterableConfigurationPropertySource {
+
+	FilteredIterableConfigurationPropertiesSource(
+			IterableConfigurationPropertySource source,
+			Predicate<ConfigurationPropertyName> filter) {
+		super(source, filter);
+	}
+
+	@Override
+	public Stream<ConfigurationPropertyName> stream() {
+		return StreamSupport.stream(getSource().spliterator(), false).filter(getFilter());
+	}
+
+	@Override
+	protected IterableConfigurationPropertySource getSource() {
+		return (IterableConfigurationPropertySource) super.getSource();
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/context/properties/source/IterableConfigurationPropertySource.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import java.util.Iterator;
+import java.util.function.Predicate;
+import java.util.stream.Stream;
+
+import org.springframework.boot.origin.OriginTrackedValue;
+
+/**
+ * A {@link ConfigurationPropertySource} with a fully {@link Iterable} set of entries.
+ * Implementations of this interface <strong>must</strong> be able to iterate over all
+ * contained configuration properties. Any {@code non-null} result from
+ * {@link #getConfigurationProperty(ConfigurationPropertyName)} must also have an
+ * equivalent entry in the {@link #iterator() iterator}.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ * @since 2.0.0
+ * @see ConfigurationPropertyName
+ * @see OriginTrackedValue
+ * @see #getConfigurationProperty(ConfigurationPropertyName)
+ * @see #iterator()
+ * @see #stream()
+ */
+public interface IterableConfigurationPropertySource
+		extends ConfigurationPropertySource, Iterable<ConfigurationPropertyName> {
+
+	/**
+	 * Return an iterator for the {@link ConfigurationPropertyName names} managed by this
+	 * source. If it is not possible to determine the names an empty iterator may be
+	 * returned.
+	 * @return an iterator (never {@code null})
+	 */
+	@Override
+	default Iterator<ConfigurationPropertyName> iterator() {
+		return stream().iterator();
+	}
+
+	/**
+	 * Returns a sequential {@code Stream} for the {@link ConfigurationPropertyName names}
+	 * managed by this source. If it is not possible to determine the names an
+	 * {@link Stream#empty() empty stream} may be returned.
+	 * @return a stream of names (never {@code null})
+	 */
+	Stream<ConfigurationPropertyName> stream();
+
+	@Override
+	default IterableConfigurationPropertySource filter(
+			Predicate<ConfigurationPropertyName> filter) {
+		return new FilteredIterableConfigurationPropertiesSource(this, filter);
+	}
+
+	@Override
+	default IterableConfigurationPropertySource withAliases(
+			ConfigurationPropertyNameAliases aliases) {
+		return new AliasedIterableConfigurationPropertySource(this, aliases);
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/context/properties/source/MapConfigurationPropertySource.java

@@ -33,11 +33,12 @@ import org.springframework.util.Assert;
  * @author Madhura Bhave
  * @since 2.0.0
  */
-public class MapConfigurationPropertySource implements ConfigurationPropertySource {
+public class MapConfigurationPropertySource
+		implements IterableConfigurationPropertySource {
 
 	private final Map<String, Object> source;
 
-	private final ConfigurationPropertySource delegate;
+	private final IterableConfigurationPropertySource delegate;
 
 	/**
 	 * Create a new empty {@link MapConfigurationPropertySource} instance.
@@ -53,7 +54,7 @@ public class MapConfigurationPropertySource implements ConfigurationPropertySour
 	 */
 	public MapConfigurationPropertySource(Map<?, ?> map) {
 		this.source = new LinkedHashMap<>();
-		this.delegate = new PropertySourceConfigurationPropertySource(
+		this.delegate = new PropertySourceIterableConfigurationPropertySource(
 				new MapPropertySource("source", this.source),
 				new DefaultPropertyMapper());
 		putAll(map);
@@ -65,6 +66,7 @@ public class MapConfigurationPropertySource implements ConfigurationPropertySour
 	 */
 	public void putAll(Map<?, ?> map) {
 		Assert.notNull(map, "Map must not be null");
+		assertNotReadOnlySystemAttributesMap(map);
 		map.forEach(this::put);
 	}
 
@@ -93,4 +95,14 @@ public class MapConfigurationPropertySource implements ConfigurationPropertySour
 		return this.delegate.stream();
 	}
 
+	private void assertNotReadOnlySystemAttributesMap(Map<?, ?> map) {
+		try {
+			map.size();
+		}
+		catch (UnsupportedOperationException ex) {
+			throw new IllegalArgumentException(
+					"Security restricted maps are not supported", ex);
+		}
+	}
+
 }

spring-boot/src/main/java/org/springframework/boot/context/properties/source/PropertySourceConfigurationPropertySource.java

@@ -16,47 +16,37 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.ArrayList;
 import java.util.Collections;
-import java.util.Iterator;
 import java.util.List;
-import java.util.stream.Stream;
+import java.util.Objects;
 
 import org.springframework.boot.origin.Origin;
 import org.springframework.boot.origin.PropertySourceOrigin;
 import org.springframework.core.env.EnumerablePropertySource;
-import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.PropertySource;
 import org.springframework.util.Assert;
-import org.springframework.util.ObjectUtils;
 
 /**
- * {@link ConfigurationPropertySource} backed by a Spring {@link PropertySource}. Provides
- * support for {@link EnumerablePropertySource} when possible but can also be used to
- * non-enumerable property sources or restricted {@link EnumerablePropertySource}
- * implementation (such as a security restricted {@code systemEnvironment} source). A
+ * {@link ConfigurationPropertySource} backed by a non-enumerable Spring
+ * {@link PropertySource} or a restricted {@link EnumerablePropertySource} implementation
+ * (such as a security restricted {@code systemEnvironment} source). A
  * {@link PropertySource} is adapted with the help of a {@link PropertyMapper} which
  * provides the mapping rules for individual properties.
  * <p>
- * Each
- * {@link ConfigurationPropertySource#getConfigurationProperty(ConfigurationPropertyName)
- * getValue} call initially attempts to
+ * Each {@link ConfigurationPropertySource#getConfigurationProperty
+ * getConfigurationProperty} call attempts to
  * {@link PropertyMapper#map(PropertySource, ConfigurationPropertyName) map} the
  * {@link ConfigurationPropertyName} to one or more {@code String} based names. This
- * allows fast property resolution for well formed property sources and allows the adapter
- * to work with non {@link EnumerablePropertySource enumerable property sources}.
+ * allows fast property resolution for well formed property sources.
  * <p>
- * If direct {@link ConfigurationPropertyName} to {@code String} mapping is unsuccessful a
- * brute force approach is taken by {@link EnumerablePropertySource#getPropertyNames()
- * enumerating} known {@code String} {@link PropertySource} names, mapping them to one or
- * more {@link ConfigurationPropertyName} and checking for
- * {@link PropertyMapping#isApplicable(ConfigurationPropertyName) applicability}. The
- * enumeration approach supports property sources where it isn't practical to guess all
- * direct mapping combinations.
+ * If at all possible the {@link PropertySourceIterableConfigurationPropertySource} should
+ * be used in preference to this implementation since it supports "relaxed" style
+ * resolution.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
  * @see PropertyMapper
+ * @see PropertySourceIterableConfigurationPropertySource
  */
 class PropertySourceConfigurationPropertySource implements ConfigurationPropertySource {
 
@@ -64,10 +54,6 @@ class PropertySourceConfigurationPropertySource implements ConfigurationProperty
 
 	private final PropertyMapper mapper;
 
-	private volatile Object cacheKey;
-
-	private volatile Cache cache;
-
 	/**
 	 * Create a new {@link PropertySourceConfigurationPropertySource} implementation.
 	 * @param propertySource the source property source
@@ -84,40 +70,19 @@ class PropertySourceConfigurationPropertySource implements ConfigurationProperty
 	@Override
 	public ConfigurationProperty getConfigurationProperty(
 			ConfigurationPropertyName name) {
-		ConfigurationProperty configurationProperty = findDirectly(name);
-		if (configurationProperty == null) {
-			configurationProperty = findByEnumeration(name);
-		}
-		return configurationProperty;
-	}
-
-	private ConfigurationProperty findDirectly(ConfigurationPropertyName name) {
-		List<PropertyMapping> mappings = this.mapper.map(this.propertySource, name);
-		return find(mappings, name);
-	}
-
-	private ConfigurationProperty findByEnumeration(ConfigurationPropertyName name) {
-		List<PropertyMapping> mappings = getPropertyMappings();
+		List<PropertyMapping> mappings = getMapper().map(getPropertySource(), name);
 		return find(mappings, name);
 	}
 
-	private ConfigurationProperty find(List<PropertyMapping> mappings,
+	protected final ConfigurationProperty find(List<PropertyMapping> mappings,
 			ConfigurationPropertyName name) {
-		// Use for-loops rather than streams since this method is called often
-		for (PropertyMapping mapping : mappings) {
-			if (mapping.isApplicable(name)) {
-				ConfigurationProperty property = find(mapping);
-				if (property != null) {
-					return property;
-				}
-			}
-		}
-		return null;
+		return mappings.stream().filter((m) -> m.isApplicable(name)).map(this::find)
+				.filter(Objects::nonNull).findFirst().orElse(null);
 	}
 
 	private ConfigurationProperty find(PropertyMapping mapping) {
 		String propertySourceName = mapping.getPropertySourceName();
-		Object value = this.propertySource.getProperty(propertySourceName);
+		Object value = getPropertySource().getProperty(propertySourceName);
 		if (value == null) {
 			return null;
 		}
@@ -128,77 +93,12 @@ class PropertySourceConfigurationPropertySource implements ConfigurationProperty
 		return ConfigurationProperty.of(configurationPropertyName, value, origin);
 	}
 
-	@Override
-	public Stream<ConfigurationPropertyName> stream() {
-		return getConfigurationPropertyNames().stream();
+	protected PropertySource<?> getPropertySource() {
+		return this.propertySource;
 	}
 
-	@Override
-	public Iterator<ConfigurationPropertyName> iterator() {
-		return getConfigurationPropertyNames().iterator();
-	}
-
-	private List<ConfigurationPropertyName> getConfigurationPropertyNames() {
-		Cache cache = getCache();
-		List<ConfigurationPropertyName> names = (cache != null ? cache.getNames() : null);
-		if (names != null) {
-			return names;
-		}
-		List<PropertyMapping> mappings = getPropertyMappings();
-		names = new ArrayList<>(mappings.size());
-		for (PropertyMapping mapping : mappings) {
-			names.add(mapping.getConfigurationPropertyName());
-		}
-		names = Collections.unmodifiableList(names);
-		if (cache != null) {
-			cache.setNames(names);
-		}
-		return names;
-	}
-
-	private List<PropertyMapping> getPropertyMappings() {
-		if (!(this.propertySource instanceof EnumerablePropertySource)) {
-			return Collections.emptyList();
-		}
-		Cache cache = getCache();
-		List<PropertyMapping> mappings = (cache != null ? cache.getMappings() : null);
-		if (mappings != null) {
-			return mappings;
-		}
-		String[] names = ((EnumerablePropertySource<?>) this.propertySource)
-				.getPropertyNames();
-		mappings = new ArrayList<>(names.length);
-		for (String name : names) {
-			mappings.addAll(this.mapper.map(this.propertySource, name));
-		}
-		mappings = Collections.unmodifiableList(mappings);
-		if (cache != null) {
-			cache.setMappings(mappings);
-		}
-		return mappings;
-	}
-
-	private Cache getCache() {
-		Object cacheKey = getCacheKey();
-		if (cacheKey == null) {
-			return null;
-		}
-		if (ObjectUtils.nullSafeEquals(cacheKey, this.cacheKey)) {
-			return this.cache;
-		}
-		this.cache = new Cache();
-		this.cacheKey = cacheKey;
-		return this.cache;
-	}
-
-	private Object getCacheKey() {
-		if (this.propertySource instanceof MapPropertySource) {
-			return ((MapPropertySource) this.propertySource).getSource().keySet();
-		}
-		if (this.propertySource instanceof EnumerablePropertySource) {
-			return ((EnumerablePropertySource<?>) this.propertySource).getPropertyNames();
-		}
-		return null;
+	protected final PropertyMapper getMapper() {
+		return this.mapper;
 	}
 
 	/**
@@ -236,28 +136,4 @@ class PropertySourceConfigurationPropertySource implements ConfigurationProperty
 
 	}
 
-	private static class Cache {
-
-		private List<ConfigurationPropertyName> names;
-
-		private List<PropertyMapping> mappings;
-
-		public List<ConfigurationPropertyName> getNames() {
-			return this.names;
-		}
-
-		public void setNames(List<ConfigurationPropertyName> names) {
-			this.names = names;
-		}
-
-		public List<PropertyMapping> getMappings() {
-			return this.mappings;
-		}
-
-		public void setMappings(List<PropertyMapping> mappings) {
-			this.mappings = mappings;
-		}
-
-	}
-
 }

spring-boot/src/main/java/org/springframework/boot/context/properties/source/PropertySourceIterableConfigurationPropertySource.java

@@ -0,0 +1,175 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.List;
+import java.util.stream.Stream;
+
+import org.springframework.core.env.EnumerablePropertySource;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.PropertySource;
+import org.springframework.core.env.SystemEnvironmentPropertySource;
+import org.springframework.util.ObjectUtils;
+
+/**
+ * {@link ConfigurationPropertySource} backed by a {@link EnumerablePropertySource}.
+ * Extends {@link PropertySourceConfigurationPropertySource} with full "relaxed" mapping
+ * support. In order to use this adapter the underlying {@link PropertySource} must be
+ * fully enumerable. A security restricted {@link SystemEnvironmentPropertySource} cannot
+ * be adapted.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ * @see PropertyMapper
+ */
+class PropertySourceIterableConfigurationPropertySource
+		extends PropertySourceConfigurationPropertySource
+		implements IterableConfigurationPropertySource {
+
+	PropertySourceIterableConfigurationPropertySource(
+			EnumerablePropertySource<?> propertySource, PropertyMapper mapper) {
+		super(propertySource, mapper);
+		assertEnumerablePropertySource(propertySource);
+	}
+
+	private void assertEnumerablePropertySource(
+			EnumerablePropertySource<?> propertySource) {
+		if (getPropertySource() instanceof MapPropertySource) {
+			try {
+				((MapPropertySource) getPropertySource()).getSource().size();
+			}
+			catch (UnsupportedOperationException ex) {
+				throw new IllegalArgumentException(
+						"PropertySource must be fully enumerable");
+			}
+		}
+	}
+
+	private volatile Object cacheKey;
+
+	private volatile Cache cache;
+
+	@Override
+	public ConfigurationProperty getConfigurationProperty(
+			ConfigurationPropertyName name) {
+		ConfigurationProperty configurationProperty = super.getConfigurationProperty(
+				name);
+		if (configurationProperty == null) {
+			configurationProperty = find(getPropertyMappings(), name);
+		}
+		return configurationProperty;
+	}
+
+	@Override
+	public Stream<ConfigurationPropertyName> stream() {
+		return getConfigurationPropertyNames().stream();
+	}
+
+	@Override
+	public Iterator<ConfigurationPropertyName> iterator() {
+		return getConfigurationPropertyNames().iterator();
+	}
+
+	private List<ConfigurationPropertyName> getConfigurationPropertyNames() {
+		Cache cache = getCache();
+		List<ConfigurationPropertyName> names = (cache != null ? cache.getNames() : null);
+		if (names != null) {
+			return names;
+		}
+		List<PropertyMapping> mappings = getPropertyMappings();
+		names = new ArrayList<>(mappings.size());
+		for (PropertyMapping mapping : mappings) {
+			names.add(mapping.getConfigurationPropertyName());
+		}
+		names = Collections.unmodifiableList(names);
+		if (cache != null) {
+			cache.setNames(names);
+		}
+		return names;
+	}
+
+	private List<PropertyMapping> getPropertyMappings() {
+		Cache cache = getCache();
+		List<PropertyMapping> mappings = (cache != null ? cache.getMappings() : null);
+		if (mappings != null) {
+			return mappings;
+		}
+		String[] names = getPropertySource().getPropertyNames();
+		mappings = new ArrayList<>(names.length);
+		for (String name : names) {
+			mappings.addAll(getMapper().map(getPropertySource(), name));
+		}
+		mappings = Collections.unmodifiableList(mappings);
+		if (cache != null) {
+			cache.setMappings(mappings);
+		}
+		return mappings;
+	}
+
+	private Cache getCache() {
+		Object cacheKey = getCacheKey();
+		if (cacheKey == null) {
+			return null;
+		}
+		if (ObjectUtils.nullSafeEquals(cacheKey, this.cacheKey)) {
+			return this.cache;
+		}
+		this.cache = new Cache();
+		this.cacheKey = cacheKey;
+		return this.cache;
+	}
+
+	private Object getCacheKey() {
+		if (getPropertySource() instanceof MapPropertySource) {
+			return ((MapPropertySource) getPropertySource()).getSource().keySet();
+		}
+		return getPropertySource().getPropertyNames();
+	}
+
+	@Override
+	protected EnumerablePropertySource<?> getPropertySource() {
+		return (EnumerablePropertySource<?>) super.getPropertySource();
+	}
+
+	private static class Cache {
+
+		private List<ConfigurationPropertyName> names;
+
+		private List<PropertyMapping> mappings;
+
+		public List<ConfigurationPropertyName> getNames() {
+			return this.names;
+		}
+
+		public void setNames(List<ConfigurationPropertyName> names) {
+			this.names = names;
+		}
+
+		public List<PropertyMapping> getMappings() {
+			return this.mappings;
+		}
+
+		public void setMappings(List<PropertyMapping> mappings) {
+			this.mappings = mappings;
+		}
+
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/context/properties/bind/ArrayBinderTests.java

@@ -167,8 +167,7 @@ public class ArrayBinderTests {
 		source.put("foo[1]", "2");
 		source.put("foo[0]", "1");
 		source.put("foo[2]", "3");
-		source.setNonIterable(true);
-		this.sources.add(source);
+		this.sources.add(source.nonIterable());
 		Integer[] result = this.binder.bind("foo", INTEGER_ARRAY).get();
 		assertThat(result).containsExactly(1, 2, 3);
 	}

spring-boot/src/test/java/org/springframework/boot/context/properties/bind/BinderTests.java

@@ -175,8 +175,7 @@ public class BinderTests {
 			throws Exception {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource(
 				"foo.value", "bar");
-		source.setNonIterable(true);
-		this.sources.add(source);
+		this.sources.add(source.nonIterable());
 		JavaBean result = this.binder.bind("foo", Bindable.of(JavaBean.class)).get();
 		assertThat(result.getValue()).isEqualTo("bar");
 	}

spring-boot/src/test/java/org/springframework/boot/context/properties/bind/CollectionBinderTests.java

@@ -48,8 +48,7 @@ public class CollectionBinderTests {
 	private static final Bindable<List<String>> STRING_LIST = Bindable
 			.listOf(String.class);
 
-	private static final Bindable<Set<String>> STRING_SET = Bindable
-			.setOf(String.class);
+	private static final Bindable<Set<String>> STRING_SET = Bindable.setOf(String.class);
 
 	private List<ConfigurationPropertySource> sources = new ArrayList<>();
 
@@ -140,8 +139,7 @@ public class CollectionBinderTests {
 		source.put("foo[1]", "2");
 		source.put("foo[0]", "1");
 		source.put("foo[2]", "3");
-		source.setNonIterable(true);
-		this.sources.add(source);
+		this.sources.add(source.nonIterable());
 		List<Integer> result = this.binder.bind("foo", INTEGER_LIST).get();
 		assertThat(result).containsExactly(1, 2, 3);
 	}
@@ -267,7 +265,8 @@ public class CollectionBinderTests {
 	}
 
 	@Test
-	public void bindToCollectionWhenEmptyStringShouldReturnEmptyCollection() throws Exception {
+	public void bindToCollectionWhenEmptyStringShouldReturnEmptyCollection()
+			throws Exception {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo", "");
 		this.sources.add(source);

spring-boot/src/test/java/org/springframework/boot/context/properties/bind/JavaBeanBinderTests.java

@@ -294,8 +294,7 @@ public class JavaBeanBinderTests {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo.value-bean.int-value", "123");
 		source.put("foo.value-bean.string-value", "foo");
-		source.setNonIterable(true);
-		this.sources.add(source);
+		this.sources.add(source.nonIterable());
 		BindResult<ExampleNestedBeanWithoutSetterOrType> bean = this.binder.bind("foo",
 				Bindable.of(ExampleNestedBeanWithoutSetterOrType.class));
 		assertThat(bean.isBound()).isFalse();
@@ -423,8 +422,7 @@ public class JavaBeanBinderTests {
 	public void bindToClassShouldNotInvokeExtraMethods() throws Exception {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource(
 				"foo.value", "123");
-		source.setNonIterable(true);
-		this.sources.add(source);
+		this.sources.add(source.nonIterable());
 		ExampleWithThrowingGetters bean = this.binder
 				.bind("foo", Bindable.of(ExampleWithThrowingGetters.class)).get();
 		assertThat(bean.getValue()).isEqualTo(123);

spring-boot/src/test/java/org/springframework/boot/context/properties/source/AliasedConfigurationPropertySourceTests.java

@@ -28,25 +28,12 @@ import static org.assertj.core.api.Assertions.assertThat;
  */
 public class AliasedConfigurationPropertySourceTests {
 
-	@Test
-	public void streamShouldInclueAliases() throws Exception {
-		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
-		source.put("foo.bar", "bing");
-		source.put("foo.baz", "biff");
-		ConfigurationPropertySource aliased = source
-				.withAliases(new ConfigurationPropertyNameAliases("foo.bar", "foo.bar1"));
-		assertThat(aliased.stream()).containsExactly(
-				ConfigurationPropertyName.of("foo.bar"),
-				ConfigurationPropertyName.of("foo.bar1"),
-				ConfigurationPropertyName.of("foo.baz"));
-	}
-
 	@Test
 	public void getConfigurationPropertyShouldConsiderAliases() throws Exception {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo.bar", "bing");
 		source.put("foo.baz", "biff");
-		ConfigurationPropertySource aliased = source
+		ConfigurationPropertySource aliased = source.nonIterable()
 				.withAliases(new ConfigurationPropertyNameAliases("foo.bar", "foo.bar1"));
 		assertThat(getValue(aliased, "foo.bar")).isEqualTo("bing");
 		assertThat(getValue(aliased, "foo.bar1")).isEqualTo("bing");
@@ -58,7 +45,7 @@ public class AliasedConfigurationPropertySourceTests {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo.bar", "bing");
 		source.put("foo.baz", "biff");
-		ConfigurationPropertySource aliased = source
+		ConfigurationPropertySource aliased = source.nonIterable()
 				.withAliases(new ConfigurationPropertyNameAliases("foo.bar", "foo.bar1"));
 		assertThat(getValue(aliased, "foo.baz")).isEqualTo("biff");
 	}

spring-boot/src/test/java/org/springframework/boot/context/properties/source/AliasedIterableConfigurationPropertySourceTests.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link AliasedConfigurationPropertySource}.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ */
+public class AliasedIterableConfigurationPropertySourceTests
+		extends AliasedConfigurationPropertySourceTests {
+
+	@Test
+	public void streamShouldInclueAliases() throws Exception {
+		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
+		source.put("foo.bar", "bing");
+		source.put("foo.baz", "biff");
+		IterableConfigurationPropertySource aliased = source
+				.withAliases(new ConfigurationPropertyNameAliases("foo.bar", "foo.bar1"));
+		assertThat(aliased.stream()).containsExactly(
+				ConfigurationPropertyName.of("foo.bar"),
+				ConfigurationPropertyName.of("foo.bar1"),
+				ConfigurationPropertyName.of("foo.baz"));
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/context/properties/source/ConfigurationPropertySourcesTests.java

@@ -25,6 +25,7 @@ import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.ExpectedException;
 
+import org.springframework.boot.env.RandomValuePropertySource;
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.MutablePropertySources;
@@ -142,6 +143,64 @@ public class ConfigurationPropertySourcesTests {
 		assertThat(sources.size()).isEqualTo(1);
 	}
 
+	@Test
+	public void getWhenNonEnumerableShouldNotBeIterable() throws Exception {
+		StandardEnvironment environment = new StandardEnvironment();
+		Map<String, Object> source = new LinkedHashMap<String, Object>() {
+
+			@Override
+			public int size() {
+				throw new UnsupportedOperationException("Same as security restricted");
+			}
+
+		};
+		PropertySource<?> propertySource = new MapPropertySource("test", source);
+		environment.getPropertySources().addFirst(propertySource);
+		ConfigurationPropertySources sources = ConfigurationPropertySources
+				.get(environment);
+		ConfigurationPropertySource configurationPropertySource = sources.iterator()
+				.next();
+		assertThat(configurationPropertySource)
+				.isNotInstanceOf(IterableConfigurationPropertySource.class);
+	}
+
+	@Test
+	public void getWhenEnumerableButRestrictedShouldNotBeIterable() throws Exception {
+		StandardEnvironment environment = new StandardEnvironment();
+		PropertySource<?> propertySource = new PropertySource<Object>("test",
+				new Object()) {
+
+			@Override
+			public Object getProperty(String name) {
+				return null;
+			}
+
+		};
+		environment.getPropertySources().addFirst(propertySource);
+		ConfigurationPropertySources sources = ConfigurationPropertySources
+				.get(environment);
+		ConfigurationPropertySource configurationPropertySource = sources.iterator()
+				.next();
+		assertThat(configurationPropertySource)
+				.isNotInstanceOf(IterableConfigurationPropertySource.class);
+	}
+
+	@Test
+	public void getWhenEnumerableShouldBeIterable() throws Exception {
+		StandardEnvironment environment = new StandardEnvironment();
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("fooBar", "Spring ${barBaz} ${bar-baz}");
+		source.put("barBaz", "Boot");
+		PropertySource<?> propertySource = new MapPropertySource("test", source);
+		environment.getPropertySources().addFirst(propertySource);
+		ConfigurationPropertySources sources = ConfigurationPropertySources
+				.get(environment);
+		ConfigurationPropertySource configurationPropertySource = sources.iterator()
+				.next();
+		assertThat(configurationPropertySource)
+				.isInstanceOf(IterableConfigurationPropertySource.class);
+	}
+
 	@Test
 	public void environmentProperyExpansionShouldWorkWhenAttached() throws Exception {
 		StandardEnvironment environment = new StandardEnvironment();
@@ -177,4 +236,22 @@ public class ConfigurationPropertySourcesTests {
 		assertThat(configurationSources.iterator()).hasSize(5);
 	}
 
+	@Test
+	public void containsDescendantOfForRandomSourceShouldDetectNamesStartingRandom()
+			throws Exception {
+		StandardEnvironment environment = new StandardEnvironment();
+		environment.getPropertySources().addFirst(new RandomValuePropertySource());
+		ConfigurationPropertySource source = ConfigurationPropertySources.get(environment)
+				.iterator().next();
+		assertThat(source.containsDescendantOf(ConfigurationPropertyName.of("")))
+				.contains(true);
+		assertThat(source.containsDescendantOf(ConfigurationPropertyName.of("random")))
+				.contains(true);
+		assertThat(source.containsDescendantOf(ConfigurationPropertyName.of("other")))
+				.contains(false);
+		assertThat(
+				source.containsDescendantOf(ConfigurationPropertyName.of("random.foo")))
+						.contains(false);
+	}
+
 }

spring-boot/src/test/java/org/springframework/boot/context/properties/source/FilteredConfigurationPropertiesSourceTests.java

@@ -25,7 +25,7 @@ import org.junit.rules.ExpectedException;
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
- * Test for {@link FilteredConfigurationPropertiesSource}.
+ * Test for {@link FilteredIterableConfigurationPropertiesSource}.
  *
  * @author Phillip Webb
  * @author Madhura Bhave
@@ -50,17 +50,9 @@ public class FilteredConfigurationPropertiesSourceTests {
 				null);
 	}
 
-	@Test
-	public void iteratorShouldFilterNames() throws Exception {
-		MockConfigurationPropertySource source = createTestSource();
-		ConfigurationPropertySource filtered = source.filter(this::noBrackets);
-		assertThat(filtered.iterator()).extracting(ConfigurationPropertyName::toString)
-				.containsExactly("a", "b", "c");
-	}
-
 	@Test
 	public void getValueShouldFilterNames() throws Exception {
-		MockConfigurationPropertySource source = createTestSource();
+		ConfigurationPropertySource source = createTestSource();
 		ConfigurationPropertySource filtered = source.filter(this::noBrackets);
 		ConfigurationPropertyName name = ConfigurationPropertyName.of("a");
 		assertThat(source.getConfigurationProperty(name).getValue()).isEqualTo("1");
@@ -72,14 +64,19 @@ public class FilteredConfigurationPropertiesSourceTests {
 
 	}
 
-	private MockConfigurationPropertySource createTestSource() {
+	protected final ConfigurationPropertySource createTestSource() {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("a", "1");
 		source.put("a[1]", "2");
 		source.put("b", "3");
 		source.put("b[1]", "4");
 		source.put("c", "5");
-		return source;
+		return convertSource(source);
+	}
+
+	protected ConfigurationPropertySource convertSource(
+			MockConfigurationPropertySource source) {
+		return source.nonIterable();
 	}
 
 	private boolean noBrackets(ConfigurationPropertyName name) {

spring-boot/src/test/java/org/springframework/boot/context/properties/source/FilteredIterableConfigurationPropertiesSourceTests.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import org.junit.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Test for {@link FilteredIterableConfigurationPropertiesSource}.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ */
+public class FilteredIterableConfigurationPropertiesSourceTests
+		extends FilteredConfigurationPropertiesSourceTests {
+
+	@Test
+	public void iteratorShouldFilterNames() throws Exception {
+		MockConfigurationPropertySource source = (MockConfigurationPropertySource) createTestSource();
+		IterableConfigurationPropertySource filtered = source.filter(this::noBrackets);
+		assertThat(filtered.iterator()).extracting(ConfigurationPropertyName::toString)
+				.containsExactly("a", "b", "c");
+	}
+
+	@Override
+	protected ConfigurationPropertySource convertSource(
+			MockConfigurationPropertySource source) {
+		return source;
+	}
+
+	private boolean noBrackets(ConfigurationPropertyName name) {
+		return name.toString().indexOf("[") == -1;
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/context/properties/source/MockConfigurationPropertySource.java

@@ -16,7 +16,6 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.Collections;
 import java.util.Iterator;
 import java.util.LinkedHashMap;
 import java.util.Map;
@@ -31,12 +30,11 @@ import org.springframework.boot.origin.OriginTrackedValue;
  * @author Phillip Webb
  * @author Madhura Bhave
  */
-public class MockConfigurationPropertySource implements ConfigurationPropertySource {
+public class MockConfigurationPropertySource
+		implements IterableConfigurationPropertySource {
 
 	private final Map<ConfigurationPropertyName, OriginTrackedValue> map = new LinkedHashMap<>();
 
-	private boolean nonIterable;
-
 	public MockConfigurationPropertySource() {
 	}
 
@@ -63,23 +61,17 @@ public class MockConfigurationPropertySource implements ConfigurationPropertySou
 		this.map.put(name, value);
 	}
 
-	public void setNonIterable(boolean nonIterable) {
-		this.nonIterable = nonIterable;
+	public ConfigurationPropertySource nonIterable() {
+		return new NonIterable();
 	}
 
 	@Override
 	public Iterator<ConfigurationPropertyName> iterator() {
-		if (this.nonIterable) {
-			return Collections.<ConfigurationPropertyName>emptyList().iterator();
-		}
 		return this.map.keySet().iterator();
 	}
 
 	@Override
 	public Stream<ConfigurationPropertyName> stream() {
-		if (this.nonIterable) {
-			return Collections.<ConfigurationPropertyName>emptyList().stream();
-		}
 		return this.map.keySet().stream();
 	}
 
@@ -97,4 +89,14 @@ public class MockConfigurationPropertySource implements ConfigurationPropertySou
 		return this.map.get(name);
 	}
 
+	private class NonIterable implements ConfigurationPropertySource {
+
+		@Override
+		public ConfigurationProperty getConfigurationProperty(
+				ConfigurationPropertyName name) {
+			return MockConfigurationPropertySource.this.getConfigurationProperty(name);
+		}
+
+	}
+
 }

spring-boot/src/test/java/org/springframework/boot/context/properties/source/PropertySourceConfigurationPropertySourceTests.java

@@ -16,11 +16,8 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.Collections;
 import java.util.LinkedHashMap;
-import java.util.List;
 import java.util.Map;
-import java.util.function.Function;
 
 import org.junit.Rule;
 import org.junit.Test;
@@ -28,11 +25,8 @@ import org.junit.rules.ExpectedException;
 
 import org.springframework.boot.origin.Origin;
 import org.springframework.boot.origin.OriginLookup;
-import org.springframework.core.env.EnumerablePropertySource;
 import org.springframework.core.env.MapPropertySource;
 import org.springframework.core.env.PropertySource;
-import org.springframework.util.LinkedMultiValueMap;
-import org.springframework.util.MultiValueMap;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.mockito.Mockito.mock;
@@ -62,43 +56,13 @@ public class PropertySourceConfigurationPropertySourceTests {
 		new PropertySourceConfigurationPropertySource(mock(PropertySource.class), null);
 	}
 
-	@Test
-	public void iteratorWhenNonEnumerbleShouldReturnEmptyIterator() throws Exception {
-		Map<String, Object> source = new LinkedHashMap<>();
-		PropertySource<?> propertySource = new NonEnumerablePropertySource<>(
-				new MapPropertySource("test", source));
-		TestPropertyMapper mapper = new TestPropertyMapper();
-		PropertySourceConfigurationPropertySource adapter = new PropertySourceConfigurationPropertySource(
-				propertySource, mapper);
-		assertThat(adapter.iterator()).isEmpty();
-	}
-
-	@Test
-	public void iteratorShouldAdaptNames() throws Exception {
-		Map<String, Object> source = new LinkedHashMap<>();
-		source.put("key1", "value1");
-		source.put("key2", "value2");
-		source.put("key3", "value3");
-		source.put("key4", "value4");
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		TestPropertyMapper mapper = new TestPropertyMapper();
-		mapper.addFromProperySource("key1", "my.key1");
-		mapper.addFromProperySource("key2", "my.key2a", "my.key2b");
-		mapper.addFromProperySource("key4", "my.key4");
-		PropertySourceConfigurationPropertySource adapter = new PropertySourceConfigurationPropertySource(
-				propertySource, mapper);
-		assertThat(adapter.iterator()).extracting(Object::toString)
-				.containsExactly("my.key1", "my.key2a", "my.key2b", "my.key4");
-	}
-
 	@Test
 	public void getValueShouldUseDirectMapping() throws Exception {
 		Map<String, Object> source = new LinkedHashMap<>();
 		source.put("key1", "value1");
 		source.put("key2", "value2");
 		source.put("key3", "value3");
-		PropertySource<?> propertySource = new NonEnumerablePropertySource<>(
-				new MapPropertySource("test", source));
+		PropertySource<?> propertySource = new MapPropertySource("test", source);
 		TestPropertyMapper mapper = new TestPropertyMapper();
 		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
 		mapper.addFromConfigurationProperty(name, "key2");
@@ -107,28 +71,11 @@ public class PropertySourceConfigurationPropertySourceTests {
 		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("value2");
 	}
 
-	@Test
-	public void getValueShouldFallbackToEnumerableMapping() throws Exception {
-		Map<String, Object> source = new LinkedHashMap<>();
-		source.put("key1", "value1");
-		source.put("key2", "value2");
-		source.put("key3", "value3");
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		TestPropertyMapper mapper = new TestPropertyMapper();
-		mapper.addFromProperySource("key1", "my.missing");
-		mapper.addFromProperySource("key2", "my.k-e-y");
-		PropertySourceConfigurationPropertySource adapter = new PropertySourceConfigurationPropertySource(
-				propertySource, mapper);
-		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
-		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("value2");
-	}
-
 	@Test
 	public void getValueShouldUseExtractor() throws Exception {
 		Map<String, Object> source = new LinkedHashMap<>();
 		source.put("key", "value");
-		PropertySource<?> propertySource = new NonEnumerablePropertySource<>(
-				new MapPropertySource("test", source));
+		PropertySource<?> propertySource = new MapPropertySource("test", source);
 		TestPropertyMapper mapper = new TestPropertyMapper();
 		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
 		mapper.addFromConfigurationProperty(name, "key",
@@ -167,25 +114,6 @@ public class PropertySourceConfigurationPropertySourceTests {
 				.isEqualTo("TestOrigin key");
 	}
 
-	/**
-	 * Test {@link PropertySource} that doesn't extend {@link EnumerablePropertySource}.
-	 */
-	private static class NonEnumerablePropertySource<T> extends PropertySource<T> {
-
-		private final PropertySource<T> propertySource;
-
-		NonEnumerablePropertySource(PropertySource<T> propertySource) {
-			super(propertySource.getName(), propertySource.getSource());
-			this.propertySource = propertySource;
-		}
-
-		@Override
-		public Object getProperty(String name) {
-			return this.propertySource.getProperty(name);
-		}
-
-	}
-
 	/**
 	 * Test {@link PropertySource} that's also a {@link OriginLookup}.
 	 */
@@ -218,48 +146,4 @@ public class PropertySourceConfigurationPropertySourceTests {
 
 	}
 
-	/**
-	 * Test {@link PropertyMapper} implementation.
-	 */
-	private static class TestPropertyMapper implements PropertyMapper {
-
-		private MultiValueMap<String, PropertyMapping> fromSource = new LinkedMultiValueMap<>();
-
-		private MultiValueMap<ConfigurationPropertyName, PropertyMapping> fromConfig = new LinkedMultiValueMap<>();
-
-		public void addFromProperySource(String from, String... to) {
-			for (String configurationPropertyName : to) {
-				this.fromSource.add(from, new PropertyMapping(from,
-						ConfigurationPropertyName.of(configurationPropertyName)));
-			}
-		}
-
-		public void addFromConfigurationProperty(ConfigurationPropertyName from,
-				String... to) {
-			for (String propertySourceName : to) {
-				this.fromConfig.add(from, new PropertyMapping(propertySourceName, from));
-			}
-		}
-
-		public void addFromConfigurationProperty(ConfigurationPropertyName from,
-				String to, Function<Object, Object> extractor) {
-			this.fromConfig.add(from, new PropertyMapping(to, from, extractor));
-		}
-
-		@Override
-		public List<PropertyMapping> map(PropertySource<?> propertySource,
-				String propertySourceName) {
-			return this.fromSource.getOrDefault(propertySourceName,
-					Collections.emptyList());
-		}
-
-		@Override
-		public List<PropertyMapping> map(PropertySource<?> propertySource,
-				ConfigurationPropertyName configurationPropertyName) {
-			return this.fromConfig.getOrDefault(configurationPropertyName,
-					Collections.emptyList());
-		}
-
-	}
-
 }

spring-boot/src/test/java/org/springframework/boot/context/properties/source/PropertySourceIterableConfigurationPropertySourceTests.java

@@ -0,0 +1,196 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import org.springframework.boot.origin.Origin;
+import org.springframework.boot.origin.OriginLookup;
+import org.springframework.core.env.EnumerablePropertySource;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.PropertySource;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link PropertySourceIterableConfigurationPropertySource}.
+ *
+ * @author Phillip Webb
+ * @author Madhura Bhave
+ */
+public class PropertySourceIterableConfigurationPropertySourceTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	@Test
+	public void createWhenPropertySourceIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("PropertySource must not be null");
+		new PropertySourceIterableConfigurationPropertySource(null,
+				mock(PropertyMapper.class));
+	}
+
+	@Test
+	public void createWhenMapperIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Mapper must not be null");
+		new PropertySourceIterableConfigurationPropertySource(
+				mock(EnumerablePropertySource.class), null);
+	}
+
+	@Test
+	public void iteratorShouldAdaptNames() throws Exception {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("key1", "value1");
+		source.put("key2", "value2");
+		source.put("key3", "value3");
+		source.put("key4", "value4");
+		EnumerablePropertySource<?> propertySource = new MapPropertySource("test",
+				source);
+		TestPropertyMapper mapper = new TestPropertyMapper();
+		mapper.addFromProperySource("key1", "my.key1");
+		mapper.addFromProperySource("key2", "my.key2a", "my.key2b");
+		mapper.addFromProperySource("key4", "my.key4");
+		PropertySourceIterableConfigurationPropertySource adapter = new PropertySourceIterableConfigurationPropertySource(
+				propertySource, mapper);
+		assertThat(adapter.iterator()).extracting(Object::toString)
+				.containsExactly("my.key1", "my.key2a", "my.key2b", "my.key4");
+	}
+
+	@Test
+	public void getValueShouldUseDirectMapping() throws Exception {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("key1", "value1");
+		source.put("key2", "value2");
+		source.put("key3", "value3");
+		EnumerablePropertySource<?> propertySource = new MapPropertySource("test",
+				source);
+		TestPropertyMapper mapper = new TestPropertyMapper();
+		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
+		mapper.addFromConfigurationProperty(name, "key2");
+		PropertySourceIterableConfigurationPropertySource adapter = new PropertySourceIterableConfigurationPropertySource(
+				propertySource, mapper);
+		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("value2");
+	}
+
+	@Test
+	public void getValueShouldUseEnumerableMapping() throws Exception {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("key1", "value1");
+		source.put("key2", "value2");
+		source.put("key3", "value3");
+		EnumerablePropertySource<?> propertySource = new MapPropertySource("test",
+				source);
+		TestPropertyMapper mapper = new TestPropertyMapper();
+		mapper.addFromProperySource("key1", "my.missing");
+		mapper.addFromProperySource("key2", "my.k-e-y");
+		PropertySourceIterableConfigurationPropertySource adapter = new PropertySourceIterableConfigurationPropertySource(
+				propertySource, mapper);
+		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
+		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("value2");
+	}
+
+	@Test
+	public void getValueShouldUseExtractor() throws Exception {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("key", "value");
+		EnumerablePropertySource<?> propertySource = new MapPropertySource("test",
+				source);
+		TestPropertyMapper mapper = new TestPropertyMapper();
+		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
+		mapper.addFromConfigurationProperty(name, "key",
+				(value) -> value.toString().replace("ue", "let"));
+		PropertySourceIterableConfigurationPropertySource adapter = new PropertySourceIterableConfigurationPropertySource(
+				propertySource, mapper);
+		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("vallet");
+	}
+
+	@Test
+	public void getValueOrigin() throws Exception {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("key", "value");
+		EnumerablePropertySource<?> propertySource = new MapPropertySource("test",
+				source);
+		TestPropertyMapper mapper = new TestPropertyMapper();
+		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
+		mapper.addFromConfigurationProperty(name, "key");
+		PropertySourceIterableConfigurationPropertySource adapter = new PropertySourceIterableConfigurationPropertySource(
+				propertySource, mapper);
+		assertThat(adapter.getConfigurationProperty(name).getOrigin().toString())
+				.isEqualTo("\"key\" from property source \"test\"");
+	}
+
+	@Test
+	public void getValueWhenOriginCapableShouldIncludeSourceOrigin() throws Exception {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("key", "value");
+		EnumerablePropertySource<?> propertySource = new OriginCapablePropertySource<>(
+				new MapPropertySource("test", source));
+		TestPropertyMapper mapper = new TestPropertyMapper();
+		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
+		mapper.addFromConfigurationProperty(name, "key");
+		PropertySourceIterableConfigurationPropertySource adapter = new PropertySourceIterableConfigurationPropertySource(
+				propertySource, mapper);
+		assertThat(adapter.getConfigurationProperty(name).getOrigin().toString())
+				.isEqualTo("TestOrigin key");
+	}
+
+	/**
+	 * Test {@link PropertySource} that's also a {@link OriginLookup}.
+	 */
+	private static class OriginCapablePropertySource<T>
+			extends EnumerablePropertySource<T> implements OriginLookup<String> {
+
+		private final EnumerablePropertySource<T> propertySource;
+
+		OriginCapablePropertySource(EnumerablePropertySource<T> propertySource) {
+			super(propertySource.getName(), propertySource.getSource());
+			this.propertySource = propertySource;
+		}
+
+		@Override
+		public Object getProperty(String name) {
+			return this.propertySource.getProperty(name);
+		}
+
+		@Override
+		public String[] getPropertyNames() {
+			return this.propertySource.getPropertyNames();
+		}
+
+		@Override
+		public Origin getOrigin(String name) {
+			return new Origin() {
+
+				@Override
+				public String toString() {
+					return "TestOrigin " + name;
+				}
+
+			};
+		}
+
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/context/properties/source/TestPropertyMapper.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright 2012-2017 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.context.properties.source;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.function.Function;
+
+import org.springframework.core.env.PropertySource;
+import org.springframework.util.LinkedMultiValueMap;
+import org.springframework.util.MultiValueMap;
+
+/**
+ * Test {@link PropertyMapper} implementation.
+ */
+class TestPropertyMapper implements PropertyMapper {
+
+	private MultiValueMap<String, PropertyMapping> fromSource = new LinkedMultiValueMap<>();
+
+	private MultiValueMap<ConfigurationPropertyName, PropertyMapping> fromConfig = new LinkedMultiValueMap<>();
+
+	public void addFromProperySource(String from, String... to) {
+		for (String configurationPropertyName : to) {
+			this.fromSource.add(from, new PropertyMapping(from,
+					ConfigurationPropertyName.of(configurationPropertyName)));
+		}
+	}
+
+	public void addFromConfigurationProperty(ConfigurationPropertyName from,
+			String... to) {
+		for (String propertySourceName : to) {
+			this.fromConfig.add(from, new PropertyMapping(propertySourceName, from));
+		}
+	}
+
+	public void addFromConfigurationProperty(ConfigurationPropertyName from, String to,
+			Function<Object, Object> extractor) {
+		this.fromConfig.add(from, new PropertyMapping(to, from, extractor));
+	}
+
+	@Override
+	public List<PropertyMapping> map(PropertySource<?> propertySource,
+			String propertySourceName) {
+		return this.fromSource.getOrDefault(propertySourceName, Collections.emptyList());
+	}
+
+	@Override
+	public List<PropertyMapping> map(PropertySource<?> propertySource,
+			ConfigurationPropertyName configurationPropertyName) {
+		return this.fromConfig.getOrDefault(configurationPropertyName,
+				Collections.emptyList());
+	}
+
+}