Add flag to PropertiesConfigurationFactory to switch off placeholder resolution

The default behaviour is unchanged, but it is useful for some applications to be
able to bind without placeholder resolution (e.g. to prevent exposing system
environment variables, if the bound object is being sent over the wire).

Author: Dave Syer

spring-boot/src/main/java/org/springframework/boot/bind/PropertiesConfigurationFactory.java

@@ -86,6 +86,8 @@ public class PropertiesConfigurationFactory<T>
 
 	private ConversionService conversionService;
 
+	private boolean resolvePlaceholders = true;
+
 	/**
 	 * Create a new {@link PropertiesConfigurationFactory} instance.
 	 * @param target the target object to bind too
@@ -203,6 +205,16 @@ public void setExceptionIfInvalid(boolean exceptionIfInvalid) {
 		this.exceptionIfInvalid = exceptionIfInvalid;
 	}
 
+	/**
+	 * Flag to indicate that placeholders should be replaced during binding. Default is
+	 * true.
+	 *
+	 * @param resolvePlaceholders flag value
+	 */
+	public void setResolvePlaceholders(boolean resolvePlaceholders) {
+		this.resolvePlaceholders = resolvePlaceholders;
+	}
+
 	@Override
 	public void afterPropertiesSet() throws Exception {
 		bindPropertiesToTarget();
@@ -322,7 +334,8 @@ private PropertyValues getPropertySourcesPropertyValues(Set<String> names,
 			Iterable<String> relaxedTargetNames) {
 		PropertyNamePatternsMatcher includes = getPropertyNamePatternsMatcher(names,
 				relaxedTargetNames);
-		return new PropertySourcesPropertyValues(this.propertySources, names, includes);
+		return new PropertySourcesPropertyValues(this.propertySources, names, includes,
+				this.resolvePlaceholders);
 	}
 
 	private PropertyNamePatternsMatcher getPropertyNamePatternsMatcher(Set<String> names,

spring-boot/src/main/java/org/springframework/boot/bind/PropertySourcesPropertyValues.java

@@ -56,12 +56,15 @@ public class PropertySourcesPropertyValues implements PropertyValues {
 
 	private final ConcurrentHashMap<String, PropertySource<?>> collectionOwners = new ConcurrentHashMap<String, PropertySource<?>>();
 
+	private boolean resolvePlaceholders = true;
+
 	/**
 	 * Create a new PropertyValues from the given PropertySources.
 	 * @param propertySources a PropertySources instance
 	 */
 	public PropertySourcesPropertyValues(PropertySources propertySources) {
-		this(propertySources, (Collection<String>) null, PropertyNamePatternsMatcher.ALL);
+		this(propertySources, (Collection<String>) null, PropertyNamePatternsMatcher.ALL,
+				true);
 	}
 
 	/**
@@ -76,7 +79,7 @@ public PropertySourcesPropertyValues(PropertySources propertySources,
 			Collection<String> includePatterns,
 			Collection<String> nonEnumerableFallbackNames) {
 		this(propertySources, nonEnumerableFallbackNames,
-				new PatternPropertyNamePatternsMatcher(includePatterns));
+				new PatternPropertyNamePatternsMatcher(includePatterns), true);
 	}
 
 	/**
@@ -85,22 +88,34 @@ public PropertySourcesPropertyValues(PropertySources propertySources,
 	 * @param nonEnumerableFallbackNames the property names to try in lieu of an
 	 * {@link EnumerablePropertySource}.
 	 * @param includes the property name patterns to include
+	 * @param resolvePlaceholders flag to indicate the placeholders should be resolved
 	 */
 	PropertySourcesPropertyValues(PropertySources propertySources,
 			Collection<String> nonEnumerableFallbackNames,
-			PropertyNamePatternsMatcher includes) {
+			PropertyNamePatternsMatcher includes, boolean resolvePlaceholders) {
 		Assert.notNull(propertySources, "PropertySources must not be null");
 		Assert.notNull(includes, "Includes must not be null");
 		this.propertySources = propertySources;
 		this.nonEnumerableFallbackNames = nonEnumerableFallbackNames;
 		this.includes = includes;
+		this.resolvePlaceholders = resolvePlaceholders;
 		PropertySourcesPropertyResolver resolver = new PropertySourcesPropertyResolver(
 				propertySources);
 		for (PropertySource<?> source : propertySources) {
 			processPropertySource(source, resolver);
 		}
 	}
 
+	/**
+	 * Flag to indicate that placeholders should be replaced during binding. Default is
+	 * true.
+	 *
+	 * @param resolvePlaceholders flag value
+	 */
+	public void setResolvePlaceholders(boolean resolvePlaceholders) {
+		this.resolvePlaceholders = resolvePlaceholders;
+	}
+
 	private void processPropertySource(PropertySource<?> source,
 			PropertySourcesPropertyResolver resolver) {
 		if (source instanceof CompositePropertySource) {
@@ -138,12 +153,14 @@ private void processEnumerablePropertySource(EnumerablePropertySource<?> source,
 	private Object getEnumerableProperty(EnumerablePropertySource<?> source,
 			PropertySourcesPropertyResolver resolver, String propertyName) {
 		try {
-			return resolver.getProperty(propertyName, Object.class);
+			if (this.resolvePlaceholders) {
+				return resolver.getProperty(propertyName, Object.class);
+			}
 		}
 		catch (RuntimeException ex) {
 			// Probably could not resolve placeholders, ignore it here
-			return source.getProperty(propertyName);
 		}
+		return source.getProperty(propertyName);
 	}
 
 	private void processNonEnumerablePropertySource(PropertySource<?> source,

spring-boot/src/test/java/org/springframework/boot/bind/PropertiesConfigurationFactoryTests.java

@@ -105,6 +105,35 @@ public void systemEnvironmentBindingFailuresAreIgnored() throws Exception {
 		assertThat(foo.name).isEqualTo("bar");
 	}
 
+	@Test
+	public void systemEnvironmentBindingWithDefaults() throws Exception {
+		setupFactory();
+		MutablePropertySources propertySources = new MutablePropertySources();
+		MockPropertySource propertySource = new MockPropertySource(
+				StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME);
+		propertySource.setProperty("name", "${foo.name:bar}");
+		propertySources.addFirst(propertySource);
+		this.factory.setPropertySources(propertySources);
+		this.factory.afterPropertiesSet();
+		Foo foo = this.factory.getObject();
+		assertThat(foo.name).isEqualTo("bar");
+	}
+
+	@Test
+	public void systemEnvironmentNoResolvePlaceholders() throws Exception {
+		setupFactory();
+		MutablePropertySources propertySources = new MutablePropertySources();
+		MockPropertySource propertySource = new MockPropertySource(
+				StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME);
+		propertySource.setProperty("name", "${foo.name:bar}");
+		propertySources.addFirst(propertySource);
+		this.factory.setPropertySources(propertySources);
+		this.factory.setResolvePlaceholders(false);
+		this.factory.afterPropertiesSet();
+		Foo foo = this.factory.getObject();
+		assertThat(foo.name).isEqualTo("${foo.name:bar}");
+	}
+
 	@Test
 	public void systemPropertyBindingFailuresAreIgnored() throws Exception {
 		setupFactory();