Support constructor binding on 3rd party classes

Closes gh-18935

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBean.java

@@ -308,7 +308,7 @@ public final class ConfigurationPropertiesBean {
 		VALUE_OBJECT;
 
 		static BindMethod forType(Class<?> type) {
-			return (ConfigurationPropertiesBindConstructorProvider.INSTANCE.getBindConstructor(type) != null)
+			return (ConfigurationPropertiesBindConstructorProvider.INSTANCE.getBindConstructor(type, false) != null)
 					? VALUE_OBJECT : JAVA_BEAN;
 		}
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/ConfigurationPropertiesBindConstructorProvider.java

@@ -37,16 +37,16 @@ class ConfigurationPropertiesBindConstructorProvider implements BindConstructorP
 	static final ConfigurationPropertiesBindConstructorProvider INSTANCE = new ConfigurationPropertiesBindConstructorProvider();
 
 	@Override
-	public Constructor<?> getBindConstructor(Bindable<?> bindable) {
-		return getBindConstructor(bindable.getType().resolve());
+	public Constructor<?> getBindConstructor(Bindable<?> bindable, boolean isNestedConstructorBinding) {
+		return getBindConstructor(bindable.getType().resolve(), isNestedConstructorBinding);
 	}
 
-	Constructor<?> getBindConstructor(Class<?> type) {
+	Constructor<?> getBindConstructor(Class<?> type, boolean isNestedConstructorBinding) {
 		if (type == null) {
 			return null;
 		}
 		Constructor<?> constructor = findConstructorBindingAnnotatedConstructor(type);
-		if (constructor == null && isConstructorBindingAnnotatedType(type)) {
+		if (constructor == null && (isConstructorBindingAnnotatedType(type) || isNestedConstructorBinding)) {
 			constructor = deduceBindConstructor(type);
 		}
 		return constructor;

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

@@ -37,8 +37,10 @@ public interface BindConstructorProvider {
 	 * Return the bind constructor to use for the given bindable, or {@code null} if
 	 * constructor binding is not supported.
 	 * @param bindable the bindable to check
+	 * @param isNestedConstructorBinding if this binding is nested within a constructor
+	 * binding
 	 * @return the bind constructor or {@code null}
 	 */
-	Constructor<?> getBindConstructor(Bindable<?> bindable);
+	Constructor<?> getBindConstructor(Bindable<?> bindable, boolean isNestedConstructorBinding);
 
 }

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

@@ -522,6 +522,8 @@ public class Binder {
 
 		private final Deque<Class<?>> dataObjectBindings = new ArrayDeque<>();
 
+		private final Deque<Class<?>> constructorBindings = new ArrayDeque<>();
+
 		private ConfigurationProperty configurationProperty;
 
 		Context() {
@@ -582,6 +584,18 @@ public class Binder {
 			this.configurationProperty = null;
 		}
 
+		void pushConstructorBoundTypes(Class<?> value) {
+			this.constructorBindings.push(value);
+		}
+
+		boolean isNestedConstructorBinding() {
+			return !this.constructorBindings.isEmpty();
+		}
+
+		void popConstructorBoundTypes() {
+			this.constructorBindings.pop();
+		}
+
 		PlaceholdersResolver getPlaceholdersResolver() {
 			return Binder.this.placeholdersResolver;
 		}

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

@@ -30,7 +30,7 @@ import org.springframework.core.KotlinDetector;
 class DefaultBindConstructorProvider implements BindConstructorProvider {
 
 	@Override
-	public Constructor<?> getBindConstructor(Bindable<?> bindable) {
+	public Constructor<?> getBindConstructor(Bindable<?> bindable, boolean isNestedConstructorBinding) {
 		Class<?> type = bindable.getType().resolve();
 		if (bindable.getValue() != null || type == null) {
 			return null;

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

@@ -53,10 +53,11 @@ class ValueObjectBinder implements DataObjectBinder {
 	@Override
 	public <T> T bind(ConfigurationPropertyName name, Bindable<T> target, Binder.Context context,
 			DataObjectPropertyBinder propertyBinder) {
-		ValueObject<T> valueObject = ValueObject.get(target, this.constructorProvider);
+		ValueObject<T> valueObject = ValueObject.get(target, this.constructorProvider, context);
 		if (valueObject == null) {
 			return null;
 		}
+		context.pushConstructorBoundTypes(target.getType().resolve());
 		List<ConstructorParameter> parameters = valueObject.getConstructorParameters();
 		List<Object> args = new ArrayList<>(parameters.size());
 		boolean bound = false;
@@ -67,12 +68,13 @@ class ValueObjectBinder implements DataObjectBinder {
 			args.add(arg);
 		}
 		context.clearConfigurationProperty();
+		context.popConstructorBoundTypes();
 		return bound ? valueObject.instantiate(args) : null;
 	}
 
 	@Override
 	public <T> T create(Bindable<T> target, Binder.Context context) {
-		ValueObject<T> valueObject = ValueObject.get(target, this.constructorProvider);
+		ValueObject<T> valueObject = ValueObject.get(target, this.constructorProvider, context);
 		if (valueObject == null) {
 			return null;
 		}
@@ -104,12 +106,14 @@ class ValueObjectBinder implements DataObjectBinder {
 		abstract List<ConstructorParameter> getConstructorParameters();
 
 		@SuppressWarnings("unchecked")
-		static <T> ValueObject<T> get(Bindable<T> bindable, BindConstructorProvider constructorProvider) {
+		static <T> ValueObject<T> get(Bindable<T> bindable, BindConstructorProvider constructorProvider,
+				Binder.Context context) {
 			Class<T> type = (Class<T>) bindable.getType().resolve();
 			if (type == null || type.isEnum() || Modifier.isAbstract(type.getModifiers())) {
 				return null;
 			}
-			Constructor<?> bindConstructor = constructorProvider.getBindConstructor(bindable);
+			Constructor<?> bindConstructor = constructorProvider.getBindConstructor(bindable,
+					context.isNestedConstructorBinding());
 			if (bindConstructor == null) {
 				return null;
 			}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesBeanTests.java

@@ -213,7 +213,7 @@ class ConfigurationPropertiesBeanTests {
 		assertThat(target.getType()).isEqualTo(ResolvableType.forClass(ConstructorBindingOnConstructor.class));
 		assertThat(target.getValue()).isNull();
 		assertThat(ConfigurationPropertiesBindConstructorProvider.INSTANCE
-				.getBindConstructor(ConstructorBindingOnConstructor.class)).isNotNull();
+				.getBindConstructor(ConstructorBindingOnConstructor.class, false)).isNotNull();
 	}
 
 	@Test

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/ConfigurationPropertiesTests.java

@@ -907,6 +907,18 @@ class ConfigurationPropertiesTests {
 		load(TestConfiguration.class);
 	}
 
+	@Test
+	void loadWhenConstructorBindingWithOuterClassDeducedConstructorBound() {
+		MutablePropertySources sources = this.context.getEnvironment().getPropertySources();
+		Map<String, Object> source = new HashMap<>();
+		source.put("test.nested.outer.age", "5");
+		sources.addLast(new MapPropertySource("test", source));
+		load(ConstructorBindingWithOuterClassConstructorBoundConfiguration.class);
+		ConstructorBindingWithOuterClassConstructorBoundProperties bean = this.context
+				.getBean(ConstructorBindingWithOuterClassConstructorBoundProperties.class);
+		assertThat(bean.getNested().getOuter().getAge()).isEqualTo(5);
+	}
+
 	private AnnotationConfigApplicationContext load(Class<?> configuration, String... inlinedProperties) {
 		return load(new Class<?>[] { configuration }, inlinedProperties);
 	}
@@ -2126,6 +2138,55 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	@ConfigurationProperties("test")
+	@ConstructorBinding
+	static class ConstructorBindingWithOuterClassConstructorBoundProperties {
+
+		private final Nested nested;
+
+		ConstructorBindingWithOuterClassConstructorBoundProperties(Nested nested) {
+			this.nested = nested;
+		}
+
+		Nested getNested() {
+			return this.nested;
+		}
+
+		static class Nested {
+
+			private Outer outer;
+
+			Outer getOuter() {
+				return this.outer;
+			}
+
+			void setOuter(Outer nested) {
+				this.outer = nested;
+			}
+
+		}
+
+	}
+
+	static class Outer {
+
+		private int age;
+
+		Outer(int age) {
+			this.age = age;
+		}
+
+		int getAge() {
+			return this.age;
+		}
+
+	}
+
+	@EnableConfigurationProperties(ConstructorBindingWithOuterClassConstructorBoundProperties.class)
+	static class ConstructorBindingWithOuterClassConstructorBoundConfiguration {
+
+	}
+
 	@ConfigurationProperties("test")
 	static class MultiConstructorConfigurationListProperties {
 

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

@@ -339,7 +339,8 @@ class JavaBeanBinderTests {
 
 	@Test
 	void bindToInstanceWhenNoDefaultConstructorShouldBind() {
-		Binder binder = new Binder(this.sources, null, null, null, null, (type) -> null);
+		Binder binder = new Binder(this.sources, null, null, null, null,
+				(bindable, isNestedConstructorBinding) -> null);
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo.value", "bar");
 		this.sources.add(source);

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

@@ -103,7 +103,8 @@ class ValueObjectBinderTests {
 		this.sources.add(source);
 		Constructor<?>[] constructors = MultipleConstructorsBean.class.getDeclaredConstructors();
 		Constructor<?> constructor = (constructors[0].getParameterCount() == 1) ? constructors[0] : constructors[1];
-		Binder binder = new Binder(this.sources, null, null, null, null, (type) -> constructor);
+		Binder binder = new Binder(this.sources, null, null, null, null,
+				(bindable, isNestedConstructorBinding) -> constructor);
 		MultipleConstructorsBean bound = binder.bind("foo", Bindable.of(MultipleConstructorsBean.class)).get();
 		assertThat(bound.getIntValue()).isEqualTo(12);
 	}