Short circuit binding if possible

Update the `Binder` to short circuit potentially expensive bean binding
if there are no known child properties. The shortcut can only be applied
when all used `ConfigurationPropertySources` return a non empty
`containsDescendantOf` result. This should be the case for most
Spring Boot applications, the exception being any apps that are running
in a security restricted environment.

Fixes gh-9023

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

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.context.properties.bind;
 
+import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
 
 /**
@@ -29,15 +30,16 @@ interface BeanBinder {
 	/**
 	 * Return a bound bean instance or {@code null} if the {@link BeanBinder} does not
 	 * support the specified {@link Bindable}.
-	 * @param target the bindable to bind
-	 * @param hasKnownBindableProperties if this binder has known bindable elements. If
-	 * names from underlying {@link ConfigurationPropertySource} cannot be iterated this
-	 * method can be {@code false}, even though binding may ultimately succeed.
+	 * @param name the name being bound
+	 * @param target the bindable to bind names from underlying
+	 * {@link ConfigurationPropertySource} cannot be iterated this method can be
+	 * {@code false}, even though binding may ultimately succeed.
+	 * @param context the bind context
 	 * @param propertyBinder property binder
 	 * @param <T> The source type
 	 * @return a bound instance or {@code null}
 	 */
-	<T> T bind(Bindable<T> target, boolean hasKnownBindableProperties,
+	<T> T bind(ConfigurationPropertyName name, Bindable<T> target, BindContext context,
 			BeanPropertyBinder propertyBinder);
 
 }

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

@@ -16,6 +16,8 @@
 
 package org.springframework.boot.context.properties.bind;
 
+import java.util.stream.Stream;
+
 import org.springframework.boot.context.properties.bind.convert.BinderConversionService;
 import org.springframework.boot.context.properties.source.ConfigurationProperty;
 import org.springframework.boot.context.properties.source.ConfigurationPropertySource;
@@ -38,12 +40,19 @@ public interface BindContext {
 	int getDepth();
 
 	/**
-	 * Return the {@link ConfigurationPropertySource sources} being used by the
-	 * {@link Binder}.
+	 * Return an {@link Iterable} of the {@link ConfigurationPropertySource sources} being
+	 * used by the {@link Binder}.
 	 * @return the sources
 	 */
 	Iterable<ConfigurationPropertySource> getSources();
 
+	/**
+	 * Return a {@link Stream} of the {@link ConfigurationPropertySource sources} being
+	 * used by the {@link Binder}.
+	 * @return the sources
+	 */
+	Stream<ConfigurationPropertySource> streamSources();
+
 	/**
 	 * Return the {@link ConfigurationProperty} actually being bound or {@code null} if
 	 * the property has not yet been determined.

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

@@ -36,7 +36,6 @@ 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;
@@ -289,8 +288,8 @@ public class Binder {
 
 	private Object bindBean(ConfigurationPropertyName name, Bindable<?> target,
 			BindHandler handler, Context context) {
-		boolean hasKnownBindableProperties = hasKnownBindableProperties(name, context);
-		if (!hasKnownBindableProperties && isUnbindableBean(target)) {
+		if (containsNoDescendantOf(context.streamSources(), name)
+				|| isUnbindableBean(name, target, context)) {
 			return null;
 		}
 		BeanPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(
@@ -300,22 +299,19 @@ public class Binder {
 			return null;
 		}
 		return context.withBean(type, () -> {
-			Stream<?> boundBeans = BEAN_BINDERS.stream().map(
-					(b) -> b.bind(target, hasKnownBindableProperties, propertyBinder));
+			Stream<?> boundBeans = BEAN_BINDERS.stream()
+					.map((b) -> b.bind(name, target, context, propertyBinder));
 			return boundBeans.filter(Objects::nonNull).findFirst().orElse(null);
 		});
 	}
 
-	private boolean hasKnownBindableProperties(ConfigurationPropertyName name,
+	private boolean isUnbindableBean(ConfigurationPropertyName name, Bindable<?> target,
 			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) {
+		if (context.streamSources().map((s) -> s.containsDescendantOf(name).orElse(false))
+				.anyMatch(Boolean.TRUE::equals)) {
+			// We know there are properties to bind so we can't bypass anything
+			return false;
+		}
 		Class<?> resolved = target.getType().resolve();
 		if (resolved.isPrimitive() || NON_BEAN_CLASSES.contains(resolved)) {
 			return true;
@@ -324,6 +320,12 @@ public class Binder {
 		return packageName.startsWith("java.");
 	}
 
+	private boolean containsNoDescendantOf(Stream<ConfigurationPropertySource> sources,
+			ConfigurationPropertyName name) {
+		return sources.map((s) -> s.containsDescendantOf(name).orElse(true))
+				.allMatch(Boolean.FALSE::equals);
+	}
+
 	/**
 	 * Create a new {@link Binder} instance from the specified environment.
 	 * @param environment the environment (must be a {@link ConfigurableEnvironment})
@@ -400,19 +402,20 @@ public class Binder {
 			}
 		}
 
-		private Stream<ConfigurationPropertySource> streamSources() {
+		@Override
+		public Iterable<ConfigurationPropertySource> getSources() {
 			if (this.sourcePushCount > 0) {
-				return this.source.stream();
+				return this.source;
 			}
-			return StreamSupport.stream(Binder.this.sources.spliterator(), false);
+			return Binder.this.sources;
 		}
 
 		@Override
-		public Iterable<ConfigurationPropertySource> getSources() {
+		public Stream<ConfigurationPropertySource> streamSources() {
 			if (this.sourcePushCount > 0) {
-				return this.source;
+				return this.source.stream();
 			}
-			return Binder.this.sources;
+			return StreamSupport.stream(Binder.this.sources.spliterator(), false);
 		}
 
 		public boolean hasBoundBean(Class<?> bean) {

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

@@ -26,6 +26,7 @@ import java.util.Map;
 import java.util.function.Supplier;
 
 import org.springframework.beans.BeanUtils;
+import org.springframework.boot.context.properties.source.ConfigurationPropertyName;
 import org.springframework.core.ResolvableType;
 
 /**
@@ -37,8 +38,11 @@ import org.springframework.core.ResolvableType;
 class JavaBeanBinder implements BeanBinder {
 
 	@Override
-	public <T> T bind(Bindable<T> target, boolean hasKnownBindableProperties,
-			BeanPropertyBinder propertyBinder) {
+	public <T> T bind(ConfigurationPropertyName name, Bindable<T> target,
+			BindContext context, BeanPropertyBinder propertyBinder) {
+		boolean hasKnownBindableProperties = context.streamSources()
+				.map((s) -> s.containsDescendantOf(name).orElse(false))
+				.anyMatch(Boolean.TRUE::equals);
 		Bean<T> bean = Bean.get(target, hasKnownBindableProperties);
 		if (bean == null) {
 			return null;