Allow @ConstructorBinding to be optional

This commit makes @ConstructorBinding optional for a type
that has a single parameterized constructor. An @Autowired annotation
on any of the constructors indicates that the type should not be constructor
bound.

Since @ConstructorBinding is now deduced for a single parameterized constructor,
the annotation is no longer needed at the type level.

Closes gh-23216

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -71,11 +71,16 @@ public final class ConfigurationPropertiesBean {
 
 	private ConfigurationPropertiesBean(String name, Object instance, ConfigurationProperties annotation,
 			Bindable<?> bindTarget) {
+		this(name, instance, annotation, bindTarget, BindMethod.forType(bindTarget.getType().resolve()));
+	}
+
+	private ConfigurationPropertiesBean(String name, Object instance, ConfigurationProperties annotation,
+			Bindable<?> bindTarget, BindMethod bindMethod) {
 		this.name = name;
 		this.instance = instance;
 		this.annotation = annotation;
 		this.bindTarget = bindTarget;
-		this.bindMethod = BindMethod.forType(bindTarget.getType().resolve());
+		this.bindMethod = bindMethod;
 	}
 
 	/**
@@ -267,6 +272,9 @@ public final class ConfigurationPropertiesBean {
 		if (instance != null) {
 			bindTarget = bindTarget.withExistingValue(instance);
 		}
+		if (factory != null) {
+			return new ConfigurationPropertiesBean(name, instance, annotation, bindTarget, BindMethod.JAVA_BEAN);
+		}
 		return new ConfigurationPropertiesBean(name, instance, annotation, bindTarget);
 	}
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -17,11 +17,11 @@
 package org.springframework.boot.context.properties;
 
 import java.lang.reflect.Constructor;
+import java.util.Arrays;
 
-import org.springframework.beans.BeanUtils;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.context.properties.bind.BindConstructorProvider;
 import org.springframework.boot.context.properties.bind.Bindable;
-import org.springframework.core.KotlinDetector;
 import org.springframework.core.annotation.MergedAnnotations;
 import org.springframework.util.Assert;
 
@@ -31,10 +31,14 @@ import org.springframework.util.Assert;
  *
  * @author Madhura Bhave
  * @author Phillip Webb
+ * @since 3.0.0
  */
-class ConfigurationPropertiesBindConstructorProvider implements BindConstructorProvider {
+public class ConfigurationPropertiesBindConstructorProvider implements BindConstructorProvider {
 
-	static final ConfigurationPropertiesBindConstructorProvider INSTANCE = new ConfigurationPropertiesBindConstructorProvider();
+	/**
+	 * A shared singleton {@link ConfigurationPropertiesBindConstructorProvider} instance.
+	 */
+	public static final ConfigurationPropertiesBindConstructorProvider INSTANCE = new ConfigurationPropertiesBindConstructorProvider();
 
 	@Override
 	public Constructor<?> getBindConstructor(Bindable<?> bindable, boolean isNestedConstructorBinding) {
@@ -45,26 +49,88 @@ class ConfigurationPropertiesBindConstructorProvider implements BindConstructorP
 		if (type == null) {
 			return null;
 		}
-		Constructor<?> constructor = findConstructorBindingAnnotatedConstructor(type);
-		if (constructor == null && (isConstructorBindingType(type) || isNestedConstructorBinding)) {
-			constructor = deduceBindConstructor(type);
+		Constructors constructors = Constructors.getConstructors(type);
+		if (constructors.getBind() != null || isNestedConstructorBinding) {
+			Assert.state(!constructors.hasAutowired(),
+					() -> type.getName() + " declares @ConstructorBinding and @Autowired constructor");
 		}
-		return constructor;
+		return constructors.getBind();
 	}
 
-	private Constructor<?> findConstructorBindingAnnotatedConstructor(Class<?> type) {
-		if (isKotlinType(type)) {
-			Constructor<?> constructor = BeanUtils.findPrimaryConstructor(type);
-			if (constructor != null) {
-				return findAnnotatedConstructor(type, constructor);
+	/**
+	 * Data holder for autowired and bind constructors.
+	 */
+	static final class Constructors {
+
+		private final boolean hasAutowired;
+
+		private final Constructor<?> bind;
+
+		private Constructors(boolean hasAutowired, Constructor<?> bind) {
+			this.hasAutowired = hasAutowired;
+			this.bind = bind;
+		}
+
+		boolean hasAutowired() {
+			return this.hasAutowired;
+		}
+
+		Constructor<?> getBind() {
+			return this.bind;
+		}
+
+		static Constructors getConstructors(Class<?> type) {
+			Constructor<?>[] candidates = getCandidateConstructors(type);
+			Constructor<?> deducedBind = deduceBindConstructor(candidates);
+			if (deducedBind != null) {
+				return new Constructors(false, deducedBind);
+			}
+			boolean hasAutowiredConstructor = false;
+			Constructor<?> bind = null;
+			for (Constructor<?> candidate : candidates) {
+				if (isAutowired(candidate)) {
+					hasAutowiredConstructor = true;
+					continue;
+				}
+				bind = findAnnotatedConstructor(type, bind, candidate);
+			}
+			return new Constructors(hasAutowiredConstructor, bind);
+		}
+
+		private static Constructor<?>[] getCandidateConstructors(Class<?> type) {
+			if (isInnerClass(type)) {
+				return new Constructor<?>[0];
+			}
+			return Arrays.stream(type.getDeclaredConstructors())
+					.filter((constructor) -> isNonSynthetic(constructor, type)).toArray(Constructor[]::new);
+		}
+
+		private static boolean isInnerClass(Class<?> type) {
+			try {
+				return type.getDeclaredField("this$0").isSynthetic();
+			}
+			catch (NoSuchFieldException ex) {
+				return false;
 			}
 		}
-		return findAnnotatedConstructor(type, type.getDeclaredConstructors());
-	}
 
-	private Constructor<?> findAnnotatedConstructor(Class<?> type, Constructor<?>... candidates) {
-		Constructor<?> constructor = null;
-		for (Constructor<?> candidate : candidates) {
+		private static boolean isNonSynthetic(Constructor<?> constructor, Class<?> type) {
+			return !constructor.isSynthetic();
+		}
+
+		private static Constructor<?> deduceBindConstructor(Constructor<?>[] constructors) {
+			if (constructors.length == 1 && constructors[0].getParameterCount() > 0 && !isAutowired(constructors[0])) {
+				return constructors[0];
+			}
+			return null;
+		}
+
+		private static boolean isAutowired(Constructor<?> candidate) {
+			return MergedAnnotations.from(candidate).isPresent(Autowired.class);
+		}
+
+		private static Constructor<?> findAnnotatedConstructor(Class<?> type, Constructor<?> constructor,
+				Constructor<?> candidate) {
 			if (MergedAnnotations.from(candidate).isPresent(ConstructorBinding.class)) {
 				Assert.state(candidate.getParameterCount() > 0,
 						() -> type.getName() + " declares @ConstructorBinding on a no-args constructor");
@@ -72,45 +138,9 @@ class ConfigurationPropertiesBindConstructorProvider implements BindConstructorP
 						() -> type.getName() + " has more than one @ConstructorBinding constructor");
 				constructor = candidate;
 			}
+			return constructor;
 		}
-		return constructor;
-	}
 
-	private boolean isConstructorBindingType(Class<?> type) {
-		return isImplicitConstructorBindingType(type) || isConstructorBindingAnnotatedType(type);
-	}
-
-	private boolean isImplicitConstructorBindingType(Class<?> type) {
-		Class<?> superclass = type.getSuperclass();
-		return (superclass != null) && "java.lang.Record".equals(superclass.getName());
-	}
-
-	private boolean isConstructorBindingAnnotatedType(Class<?> type) {
-		return MergedAnnotations.from(type, MergedAnnotations.SearchStrategy.TYPE_HIERARCHY_AND_ENCLOSING_CLASSES)
-				.isPresent(ConstructorBinding.class);
-	}
-
-	private Constructor<?> deduceBindConstructor(Class<?> type) {
-		if (isKotlinType(type)) {
-			return deducedKotlinBindConstructor(type);
-		}
-		Constructor<?>[] constructors = type.getDeclaredConstructors();
-		if (constructors.length == 1 && constructors[0].getParameterCount() > 0) {
-			return constructors[0];
-		}
-		return null;
-	}
-
-	private Constructor<?> deducedKotlinBindConstructor(Class<?> type) {
-		Constructor<?> primaryConstructor = BeanUtils.findPrimaryConstructor(type);
-		if (primaryConstructor != null && primaryConstructor.getParameterCount() > 0) {
-			return primaryConstructor;
-		}
-		return null;
-	}
-
-	private boolean isKotlinType(Class<?> type) {
-		return KotlinDetector.isKotlinPresent() && KotlinDetector.isKotlinType(type);
 	}
 
 }

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

@@ -23,9 +23,10 @@ import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 
 /**
- * Annotation that can be used to indicate that configuration properties should be bound
- * using constructor arguments rather than by calling setters. Can be added at the type
- * level (if there is an unambiguous constructor) or on the actual constructor to use.
+ * Annotation that can be used to indicate which constructor to use when binding
+ * configuration properties using constructor arguments rather than by calling setters. A
+ * single parameterized constructor implicitly indicates that constructor binding should
+ * be used unless the constructor is annotated with `@Autowired`.
  * <p>
  * Note: To use constructor binding the class must be enabled using
  * {@link EnableConfigurationProperties @EnableConfigurationProperties} or configuration
@@ -39,7 +40,7 @@ import java.lang.annotation.Target;
  * @since 2.2.0
  * @see ConfigurationProperties
  */
-@Target({ ElementType.TYPE, ElementType.CONSTRUCTOR })
+@Target(ElementType.CONSTRUCTOR)
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 public @interface ConstructorBinding {

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

@@ -102,7 +102,6 @@ class ConfigurationPropertiesBeanRegistrarTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties("valuecp")
 	static class ValueObjectConfigurationProperties {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -27,6 +27,7 @@ import org.junit.jupiter.api.condition.EnabledForJreRange;
 import org.junit.jupiter.api.condition.JRE;
 import org.junit.jupiter.api.function.ThrowingConsumer;
 
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.context.properties.ConfigurationPropertiesBean.BindMethod;
 import org.springframework.boot.context.properties.bind.Bindable;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
@@ -47,6 +48,7 @@ import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
  * Tests for {@link ConfigurationPropertiesBean}.
  *
  * @author Phillip Webb
+ * @author Madhura Bhave
  */
 class ConfigurationPropertiesBeanTests {
 
@@ -266,14 +268,14 @@ class ConfigurationPropertiesBeanTests {
 	}
 
 	@Test
-	void bindTypeForTypeWhenNoConstructorBindingOnTypeReturnsValueObject() {
-		BindMethod bindType = BindMethod.forType(ConstructorBindingOnType.class);
+	void bindTypeForTypeWhenConstructorBindingOnConstructorReturnsValueObject() {
+		BindMethod bindType = BindMethod.forType(ConstructorBindingOnConstructor.class);
 		assertThat(bindType).isEqualTo(BindMethod.VALUE_OBJECT);
 	}
 
 	@Test
-	void bindTypeForTypeWhenNoConstructorBindingOnConstructorReturnsValueObject() {
-		BindMethod bindType = BindMethod.forType(ConstructorBindingOnConstructor.class);
+	void bindTypeForTypeWhenNoConstructorBindingAnnotationOnSingleParameterizedConstructorReturnsValueObject() {
+		BindMethod bindType = BindMethod.forType(ConstructorBindingNoAnnotation.class);
 		assertThat(bindType).isEqualTo(BindMethod.VALUE_OBJECT);
 	}
 
@@ -285,6 +287,42 @@ class ConfigurationPropertiesBeanTests {
 						+ " has more than one @ConstructorBinding constructor");
 	}
 
+	@Test
+	void bindTypeForTypeWithMultipleConstructorsReturnJavaBean() {
+		BindMethod bindType = BindMethod.forType(NoConstructorBindingOnMultipleConstructors.class);
+		assertThat(bindType).isEqualTo(BindMethod.JAVA_BEAN);
+	}
+
+	@Test
+	void bindTypeForTypeWithNoArgConstructorReturnsJavaBean() {
+		BindMethod bindType = BindMethod.forType(JavaBeanWithNoArgConstructor.class);
+		assertThat(bindType).isEqualTo(BindMethod.JAVA_BEAN);
+	}
+
+	@Test
+	void bindTypeForTypeWithSingleArgAutowiredConstructorReturnsJavaBean() {
+		BindMethod bindType = BindMethod.forType(JavaBeanWithAutowiredConstructor.class);
+		assertThat(bindType).isEqualTo(BindMethod.JAVA_BEAN);
+	}
+
+	@Test
+	void constructorBindingAndAutowiredConstructorsShouldThrowException() {
+		assertThatIllegalStateException()
+				.isThrownBy(() -> BindMethod.forType(ConstructorBindingAndAutowiredConstructors.class));
+	}
+
+	@Test
+	void innerClassWithSyntheticFieldShouldReturnJavaBean() {
+		BindMethod bindType = BindMethod.forType(Inner.class);
+		assertThat(bindType).isEqualTo(BindMethod.JAVA_BEAN);
+	}
+
+	@Test
+	void innerClassWithParameterizedConstructorShouldReturnJavaBean() {
+		BindMethod bindType = BindMethod.forType(ParameterizedConstructorInner.class);
+		assertThat(bindType).isEqualTo(BindMethod.JAVA_BEAN);
+	}
+
 	private void get(Class<?> configuration, String beanName, ThrowingConsumer<ConfigurationPropertiesBean> consumer)
 			throws Throwable {
 		get(configuration, beanName, true, consumer);
@@ -448,7 +486,6 @@ class ConfigurationPropertiesBeanTests {
 	}
 
 	@ConfigurationProperties
-	@ConstructorBinding
 	static class ValueObject {
 
 		ValueObject(String name) {
@@ -470,10 +507,9 @@ class ConfigurationPropertiesBeanTests {
 	}
 
 	@ConfigurationProperties
-	@ConstructorBinding
-	static class ConstructorBindingOnType {
+	static class ConstructorBindingNoAnnotation {
 
-		ConstructorBindingOnType(String name) {
+		ConstructorBindingNoAnnotation(String name) {
 		}
 
 	}
@@ -505,6 +541,48 @@ class ConfigurationPropertiesBeanTests {
 
 	}
 
+	@ConfigurationProperties
+	static class NoConstructorBindingOnMultipleConstructors {
+
+		NoConstructorBindingOnMultipleConstructors(String name) {
+			this(name, -1);
+		}
+
+		NoConstructorBindingOnMultipleConstructors(String name, int age) {
+		}
+
+	}
+
+	@ConfigurationProperties
+	static class JavaBeanWithAutowiredConstructor {
+
+		@Autowired
+		JavaBeanWithAutowiredConstructor(String name) {
+		}
+
+	}
+
+	@ConfigurationProperties
+	static class JavaBeanWithNoArgConstructor {
+
+		JavaBeanWithNoArgConstructor() {
+		}
+
+	}
+
+	@ConfigurationProperties
+	static class ConstructorBindingAndAutowiredConstructors {
+
+		@Autowired
+		ConstructorBindingAndAutowiredConstructors(String name) {
+		}
+
+		@ConstructorBinding
+		ConstructorBindingAndAutowiredConstructors(Integer age) {
+		}
+
+	}
+
 	@Configuration(proxyBeanMethods = false)
 	@Import(NonAnnotatedBeanConfigurationImportSelector.class)
 	static class NonAnnotatedBeanImportConfiguration {
@@ -520,4 +598,17 @@ class ConfigurationPropertiesBeanTests {
 
 	}
 
+	@ConfigurationProperties
+	class Inner {
+
+	}
+
+	@ConfigurationProperties
+	class ParameterizedConstructorInner {
+
+		ParameterizedConstructorInner(Integer age) {
+		}
+
+	}
+
 }

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

@@ -1049,6 +1049,16 @@ class ConfigurationPropertiesTests {
 		assertThat(bean.getNested().getOuter().getAge()).isEqualTo(5);
 	}
 
+	@Test
+	void loadWhenConstructorBindingWithOuterClassAndNestedAutowiredShouldThrowException() {
+		MutablePropertySources sources = this.context.getEnvironment().getPropertySources();
+		Map<String, Object> source = new HashMap<>();
+		source.put("test.nested.age", "5");
+		sources.addLast(new MapPropertySource("test", source));
+		assertThatExceptionOfType(ConfigurationPropertiesBindException.class).isThrownBy(
+				() -> load(ConstructorBindingWithOuterClassConstructorBoundAndNestedAutowiredConfiguration.class));
+	}
+
 	@Test
 	void loadWhenConfigurationPropertiesPrefixMatchesPropertyInEnvironment() {
 		MutablePropertySources sources = this.context.getEnvironment().getPropertySources();
@@ -2092,7 +2102,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "test")
 	static class OtherInjectedProperties {
 
@@ -2110,7 +2119,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "test")
 	@Validated
 	static class ConstructorParameterProperties {
@@ -2135,7 +2143,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "test")
 	static class ConstructorParameterWithUnitProperties {
 
@@ -2167,7 +2174,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "test")
 	static class ConstructorParameterWithFormatProperties {
 
@@ -2192,7 +2198,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "test")
 	@Validated
 	static class ConstructorParameterValidatedProperties {
@@ -2376,7 +2381,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties("test")
 	static class NestedConstructorProperties {
 
@@ -2414,7 +2418,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties("test")
 	static class NestedMultipleConstructorProperties {
 
@@ -2463,7 +2466,6 @@ class ConfigurationPropertiesTests {
 	}
 
 	@ConfigurationProperties("test")
-	@ConstructorBinding
 	static class ConstructorBindingWithOuterClassConstructorBoundProperties {
 
 		private final Nested nested;
@@ -2492,6 +2494,36 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	@ConfigurationProperties("test")
+	static class ConstructorBindingWithOuterClassConstructorBoundAndNestedAutowired {
+
+		private final Nested nested;
+
+		ConstructorBindingWithOuterClassConstructorBoundAndNestedAutowired(Nested nested) {
+			this.nested = nested;
+		}
+
+		Nested getNested() {
+			return this.nested;
+		}
+
+		static class Nested {
+
+			private int age;
+
+			@Autowired
+			Nested(int age) {
+				this.age = age;
+			}
+
+			int getAge() {
+				return this.age;
+			}
+
+		}
+
+	}
+
 	static class Outer {
 
 		private int age;
@@ -2511,6 +2543,11 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	@EnableConfigurationProperties(ConstructorBindingWithOuterClassConstructorBoundAndNestedAutowired.class)
+	static class ConstructorBindingWithOuterClassConstructorBoundAndNestedAutowiredConfiguration {
+
+	}
+
 	@ConfigurationProperties("test")
 	static class MultiConstructorConfigurationListProperties {
 
@@ -2613,7 +2650,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties("test")
 	static class SyntheticNestedConstructorProperties {
 
@@ -2667,7 +2703,6 @@ class ConfigurationPropertiesTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties("test")
 	static class DeducedNestedConstructorProperties {
 

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

@@ -61,7 +61,7 @@ class EnableConfigurationPropertiesRegistrarTests {
 	}
 
 	@Test
-	void typeWithConstructorBindingShouldRegisterConfigurationPropertiesBeanDefinition() {
+	void constructorBoundPropertiesShouldRegisterConfigurationPropertiesBeanDefinition() {
 		register(TestConfiguration.class);
 		BeanDefinition definition = this.beanFactory
 				.getBeanDefinition("bar-" + getClass().getName() + "$BarProperties");
@@ -137,7 +137,6 @@ class EnableConfigurationPropertiesRegistrarTests {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "bar")
 	static class BarProperties {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2022 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.
@@ -19,6 +19,7 @@ package org.springframework.boot.context.properties;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.beans.FatalBeanException;
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.diagnostics.FailureAnalysis;
 import org.springframework.boot.diagnostics.LoggingFailureAnalysisReporter;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
@@ -75,7 +76,6 @@ class NotConstructorBoundInjectionFailureAnalyzerTests {
 		return analysis;
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties("test")
 	static class ConstructorBoundProperties {
 
@@ -102,6 +102,7 @@ class NotConstructorBoundInjectionFailureAnalyzerTests {
 
 		private String name;
 
+		@Autowired
 		JavaBeanBoundProperties(String dependency) {
 
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/scan/valid/ConfigurationPropertiesScanConfiguration.java

@@ -18,7 +18,6 @@ package org.springframework.boot.context.properties.scan.valid;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
 import org.springframework.boot.context.properties.ConfigurationPropertiesScan;
-import org.springframework.boot.context.properties.ConstructorBinding;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.boot.context.properties.scan.valid.b.BScanConfiguration;
 
@@ -47,7 +46,6 @@ public class ConfigurationPropertiesScanConfiguration {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "bar")
 	static class BarProperties {
 

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/scan/valid/b/BScanConfiguration.java

@@ -17,7 +17,6 @@
 package org.springframework.boot.context.properties.scan.valid.b;
 
 import org.springframework.boot.context.properties.ConfigurationProperties;
-import org.springframework.boot.context.properties.ConstructorBinding;
 
 /**
  * @author Madhura Bhave
@@ -29,7 +28,6 @@ public class BScanConfiguration {
 
 	}
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "b.first")
 	public static class BFirstProperties implements BProperties {
 

spring-boot-project/spring-boot/src/test/kotlin/org/springframework/boot/context/properties/ConfigurationPropertiesBindConstructorProviderTests.kt

@@ -0,0 +1,213 @@
+/*
+ * Copyright 2012-2021 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
+ *
+ *      https://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;
+
+import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.assertThatIllegalStateException
+import org.junit.jupiter.api.Test
+import org.springframework.beans.factory.annotation.Autowired
+
+/**
+ * Tests for `ConfigurationPropertiesBindConstructorProvider`.
+ *
+ * @author Madhura Bhave
+ */
+@Suppress("unused")
+class ConfigurationPropertiesBindConstructorProviderTests {
+
+	private val constructorProvider = ConfigurationPropertiesBindConstructorProvider()
+
+	@Test
+	fun `type with default constructor should register java bean`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(FooProperties::class.java, false)
+		assertThat(bindConstructor).isNull()
+	}
+
+	@Test
+	fun `type with no primary constructor should register java bean`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(MultipleAmbiguousConstructors::class.java, false)
+		assertThat(bindConstructor).isNull()
+	}
+
+	@Test
+	fun `type with primary and secondary annotated constructor should use secondary constructor for binding`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(ConstructorBindingOnSecondaryWithPrimaryConstructor::class.java, false)
+		assertThat(bindConstructor).isNotNull();
+	}
+
+	@Test
+	fun `type with primary constructor with autowired should not use constructor binding`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(AutowiredPrimaryProperties::class.java, false)
+		assertThat(bindConstructor).isNull()
+	}
+
+	@Test
+	fun `type with primary and secondary constructor with autowired should not use constructor binding`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(PrimaryWithAutowiredSecondaryProperties::class.java, false)
+		assertThat(bindConstructor).isNull()
+	}
+
+	@Test
+	fun `type with autowired secondary constructor should not use constructor binding`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(AutowiredSecondaryProperties::class.java, false)
+		assertThat(bindConstructor).isNull()
+	}
+
+	@Test
+	fun `type with autowired primary and constructor binding on secondary constructor should throw exception`() {
+		assertThatIllegalStateException().isThrownBy {
+			this.constructorProvider.getBindConstructor(ConstructorBindingOnSecondaryAndAutowiredPrimaryProperties::class.java, false)
+		}
+	}
+
+	@Test
+	fun `type with autowired secondary and constructor binding on primary constructor should throw exception`() {
+		assertThatIllegalStateException().isThrownBy {
+			this.constructorProvider.getBindConstructor(ConstructorBindingOnPrimaryAndAutowiredSecondaryProperties::class.java, false)
+		}
+	}
+
+	@Test
+	fun `type with primary constructor and no annotation should use constructor binding`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(ConstructorBindingPrimaryConstructorNoAnnotation::class.java, false)
+		assertThat(bindConstructor).isNotNull()
+	}
+
+	@Test
+	fun `type with secondary constructor and no annotation should use constructor binding`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(ConstructorBindingSecondaryConstructorNoAnnotation::class.java, false)
+		assertThat(bindConstructor).isNotNull()
+	}
+
+	@Test
+	fun `type with multiple constructors`() {
+		val bindConstructor = this.constructorProvider.getBindConstructor(ConstructorBindingMultipleConstructors::class.java, false)
+		assertThat(bindConstructor).isNotNull()
+	}
+
+	@Test
+	fun `type with multiple annotated constructors should throw exception`() {
+		assertThatIllegalStateException().isThrownBy {
+			this.constructorProvider.getBindConstructor(ConstructorBindingMultipleAnnotatedConstructors::class.java, false)
+		}
+	}
+
+	@Test
+	fun `type with secondary and primary annotated constructors should throw exception`() {
+		assertThatIllegalStateException().isThrownBy {
+			this.constructorProvider.getBindConstructor(ConstructorBindingSecondaryAndPrimaryAnnotatedConstructors::class.java, false)
+		}
+	}
+
+	@ConfigurationProperties(prefix = "foo")
+	class FooProperties
+
+	@ConfigurationProperties(prefix = "bar")
+	class PrimaryWithAutowiredSecondaryProperties constructor(val name: String?, val counter: Int = 42) {
+
+		@Autowired
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String) : this(foo, 21)
+	}
+
+	@ConfigurationProperties(prefix = "bar")
+	class AutowiredSecondaryProperties {
+
+		@Autowired
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String)
+	}
+
+	@ConfigurationProperties(prefix = "bar")
+	class AutowiredPrimaryProperties @Autowired constructor(val name: String?, val counter: Int = 42) {
+
+	}
+
+	@ConfigurationProperties(prefix = "bar")
+	class ConstructorBindingOnSecondaryAndAutowiredPrimaryProperties @Autowired constructor(val name: String?, val counter: Int = 42) {
+
+		@ConstructorBinding
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String) : this(foo, 21)
+	}
+
+	@ConfigurationProperties(prefix = "bar")
+	class ConstructorBindingOnPrimaryAndAutowiredSecondaryProperties @ConstructorBinding constructor(val name: String?, val counter: Int = 42) {
+
+		@Autowired
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String) : this(foo, 21)
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingOnSecondaryWithPrimaryConstructor constructor(val name: String?, val counter: Int = 42) {
+
+		@ConstructorBinding
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String) : this(foo, 21)
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingOnPrimaryWithSecondaryConstructor @ConstructorBinding constructor(val name: String?, val counter: Int = 42) {
+
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String) : this(foo, 21)
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingPrimaryConstructorNoAnnotation(val name: String?, val counter: Int = 42)
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingSecondaryConstructorNoAnnotation {
+
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String)
+
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class MultipleAmbiguousConstructors {
+
+		constructor()
+
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String)
+
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingMultipleConstructors {
+
+		constructor(@Suppress("UNUSED_PARAMETER") bar: Int)
+
+		@ConstructorBinding
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String)
+
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingMultipleAnnotatedConstructors {
+
+		@ConstructorBinding
+		constructor(@Suppress("UNUSED_PARAMETER") bar: Int)
+
+		@ConstructorBinding
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String)
+
+	}
+
+	@ConfigurationProperties(prefix = "bing")
+	class ConstructorBindingSecondaryAndPrimaryAnnotatedConstructors @ConstructorBinding constructor(val name: String?, val counter: Int = 42) {
+
+		@ConstructorBinding
+		constructor(@Suppress("UNUSED_PARAMETER") foo: String) : this(foo, 21)
+
+	}
+
+}

spring-boot-project/spring-boot/src/test/kotlin/org/springframework/boot/context/properties/KotlinConfigurationPropertiesBeanRegistrarTests.kt

@@ -32,7 +32,7 @@ class KotlinConfigurationPropertiesBeanRegistrarTests {
 				"bar-org.springframework.boot.context.properties.KotlinConfigurationPropertiesBeanRegistrarTests\$BarProperties")
 		assertThat(beanDefinition.hasAttribute(ConfigurationPropertiesBean.BindMethod::class.java.name)).isTrue()
 		assertThat(beanDefinition.getAttribute(ConfigurationPropertiesBean.BindMethod::class.java.name))
-			.isEqualTo(ConfigurationPropertiesBean.BindMethod.VALUE_OBJECT)
+				.isEqualTo(ConfigurationPropertiesBean.BindMethod.VALUE_OBJECT)
 	}
 
 	@Test
@@ -46,7 +46,6 @@ class KotlinConfigurationPropertiesBeanRegistrarTests {
 	@ConfigurationProperties(prefix = "foo")
 	class FooProperties
 
-	@ConstructorBinding
 	@ConfigurationProperties(prefix = "bar")
 	class BarProperties(val name: String?, val counter: Int = 42)
 

spring-boot-project/spring-boot/src/test/kotlin/org/springframework/boot/context/properties/KotlinConfigurationPropertiesTests.kt

@@ -26,7 +26,6 @@ class KotlinConfigurationPropertiesTests {
 	}
 
 	@ConfigurationProperties(prefix = "foo")
-	@ConstructorBinding
 	class BingProperties(@Suppress("UNUSED_PARAMETER") bar: String) {
 
 	}