Do not attempt constructor binding for items with an existing value

Update `DefaultBindConstructorProvider` so that it no longer detects
constructors when the `Bindable` has an existing value. This update
allows us change `ConfigurationPropertiesBindingPostProcessor` and
related classes so that all instances created from `@Bean` methods
are treated as `JAVA_BEAN` bindings and will not be accidentally
re-created using constructor binding.

Fixes gh-33710

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -71,18 +71,13 @@ public final class ConfigurationPropertiesBean {
 
 	private final BindMethod bindMethod;
 
-	private ConfigurationPropertiesBean(String name, Object instance, ConfigurationProperties annotation,
-			Bindable<?> bindable) {
-		this(name, instance, annotation, bindable, BindMethod.get(bindable));
-	}
-
 	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;
+		this.bindMethod = (bindMethod != null) ? bindMethod : BindMethod.get(bindTarget);
 	}
 
 	/**
@@ -168,7 +163,8 @@ public final class ConfigurationPropertiesBean {
 			if (isConfigurationPropertiesBean(beanFactory, beanName)) {
 				try {
 					Object bean = beanFactory.getBean(beanName);
-					ConfigurationPropertiesBean propertiesBean = get(applicationContext, bean, beanName);
+					BindMethod bindMethod = getBindMethod(beanFactory, beanName);
+					ConfigurationPropertiesBean propertiesBean = get(applicationContext, bean, beanName, bindMethod);
 					if (propertiesBean != null) {
 						propertiesBeans.put(beanName, propertiesBean);
 					}
@@ -180,6 +176,16 @@ public final class ConfigurationPropertiesBean {
 		return propertiesBeans;
 	}
 
+	private static BindMethod getBindMethod(ConfigurableListableBeanFactory beanFactory, String beanName) {
+		try {
+			BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanName);
+			return (BindMethod) beanDefinition.getAttribute(BindMethod.class.getName());
+		}
+		catch (NoSuchBeanDefinitionException ex) {
+			return null;
+		}
+	}
+
 	private static boolean isConfigurationPropertiesBean(ConfigurableListableBeanFactory beanFactory, String beanName) {
 		try {
 			if (beanFactory.getBeanDefinition(beanName).isAbstract()) {
@@ -210,8 +216,13 @@ public final class ConfigurationPropertiesBean {
 	 * {@link ConfigurationProperties @ConfigurationProperties}
 	 */
 	public static ConfigurationPropertiesBean get(ApplicationContext applicationContext, Object bean, String beanName) {
+		return get(applicationContext, bean, beanName, null);
+	}
+
+	private static ConfigurationPropertiesBean get(ApplicationContext applicationContext, Object bean, String beanName,
+			BindMethod bindMethod) {
 		Method factoryMethod = findFactoryMethod(applicationContext, beanName);
-		return create(beanName, bean, bean.getClass(), factoryMethod);
+		return create(beanName, bean, bean.getClass(), factoryMethod, bindMethod);
 	}
 
 	private static Method findFactoryMethod(ApplicationContext applicationContext, String beanName) {
@@ -260,13 +271,14 @@ public final class ConfigurationPropertiesBean {
 	}
 
 	static ConfigurationPropertiesBean forValueObject(Class<?> beanClass, String beanName) {
-		ConfigurationPropertiesBean propertiesBean = create(beanName, null, beanClass, null);
+		ConfigurationPropertiesBean propertiesBean = create(beanName, null, beanClass, null, null);
 		Assert.state(propertiesBean != null && propertiesBean.getBindMethod() == BindMethod.VALUE_OBJECT,
 				() -> "Bean '" + beanName + "' is not a @ConfigurationProperties value object");
 		return propertiesBean;
 	}
 
-	private static ConfigurationPropertiesBean create(String name, Object instance, Class<?> type, Method factory) {
+	private static ConfigurationPropertiesBean create(String name, Object instance, Class<?> type, Method factory,
+			BindMethod bindMethod) {
 		ConfigurationProperties annotation = findAnnotation(instance, type, factory, ConfigurationProperties.class);
 		if (annotation == null) {
 			return null;
@@ -277,13 +289,11 @@ public final class ConfigurationPropertiesBean {
 		ResolvableType bindType = (factory != null) ? ResolvableType.forMethodReturnType(factory)
 				: ResolvableType.forClass(type);
 		Bindable<Object> bindable = Bindable.of(bindType).withAnnotations(annotations);
-		if (instance != null) {
+		bindMethod = (factory != null) ? BindMethod.JAVA_BEAN : bindMethod;
+		if (instance != null && bindMethod != BindMethod.VALUE_OBJECT) {
 			bindable = bindable.withExistingValue(instance);
 		}
-		if (factory != null) {
-			return new ConfigurationPropertiesBean(name, instance, annotation, bindable, BindMethod.JAVA_BEAN);
-		}
-		return new ConfigurationPropertiesBean(name, instance, annotation, bindable);
+		return new ConfigurationPropertiesBean(name, instance, annotation, bindable, bindMethod);
 	}
 
 	private static <A extends Annotation> A findAnnotation(Object instance, Class<?> type, Method factory,

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -75,12 +75,19 @@ public class ConfigurationPropertiesBindingPostProcessor
 
 	@Override
 	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
+		if (!hasBoundValueObject(beanName)) {
 			bind(ConfigurationPropertiesBean.get(this.applicationContext, bean, beanName));
+		}
 		return bean;
 	}
 
+	private boolean hasBoundValueObject(String beanName) {
+		return this.registry.containsBeanDefinition(beanName) && BindMethod.VALUE_OBJECT
+				.equals(this.registry.getBeanDefinition(beanName).getAttribute(BindMethod.class.getName()));
+	}
+
 	private void bind(ConfigurationPropertiesBean bean) {
-		if (bean == null || hasBoundValueObject(bean.getName())) {
+		if (bean == null) {
 			return;
 		}
 		Assert.state(bean.getBindMethod() == BindMethod.JAVA_BEAN, "Cannot bind @ConfigurationProperties for bean '"
@@ -93,11 +100,6 @@ public class ConfigurationPropertiesBindingPostProcessor
 		}
 	}
 
-	private boolean hasBoundValueObject(String beanName) {
-		return this.registry.containsBeanDefinition(beanName) && BindMethod.VALUE_OBJECT
-				.equals(this.registry.getBeanDefinition(beanName).getAttribute(BindMethod.class.getName()));
-	}
-
 	/**
 	 * Register a {@link ConfigurationPropertiesBindingPostProcessor} bean if one is not
 	 * already registered.

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2021 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -90,6 +90,18 @@ public final class Bindable<T> {
 		return this.value;
 	}
 
+	/**
+	 * Return if the bindable is for an existing non-null value. If this method return
+	 * true then {@link #getValue()} will return a {@link Supplier} that never returns
+	 * {@code null}.
+	 * @return if the {@link Bindable} is for an existing value
+	 * @since 3.0.2
+	 * @see #withExistingValue(Object)
+	 */
+	public boolean hasExistingValue() {
+		return this.value instanceof ExistingValueSupplier;
+	}
+
 	/**
 	 * Return any associated annotations that could affect binding.
 	 * @return the associated annotations
@@ -182,7 +194,7 @@ public final class Bindable<T> {
 		Assert.isTrue(
 				existingValue == null || this.type.isArray() || this.boxedType.resolve().isInstance(existingValue),
 				() -> "ExistingValue must be an instance of " + this.type);
-		Supplier<T> value = (existingValue != null) ? () -> existingValue : null;
+		Supplier<T> value = (existingValue != null) ? new ExistingValueSupplier(existingValue) : null;
 		return new Bindable<>(this.type, this.boxedType, value, this.annotations, this.bindRestrictions);
 	}
 
@@ -307,4 +319,20 @@ public final class Bindable<T> {
 
 	}
 
+	private class ExistingValueSupplier implements Supplier<T> {
+
+		private final T value;
+
+		ExistingValueSupplier(T value) {
+			Assert.notNull(value, "Value must not be null");
+			this.value = value;
+		}
+
+		@Override
+		public T get() {
+			return this.value;
+		}
+
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -39,12 +39,18 @@ class DefaultBindConstructorProvider implements BindConstructorProvider {
 
 	@Override
 	public Constructor<?> getBindConstructor(Bindable<?> bindable, boolean isNestedConstructorBinding) {
-		return getBindConstructor(bindable.getType().resolve(), isNestedConstructorBinding);
+		return getBindConstructor(bindable.getType().resolve(), bindable.hasExistingValue(),
+				isNestedConstructorBinding);
 	}
 
 	@Override
 	public Constructor<?> getBindConstructor(Class<?> type, boolean isNestedConstructorBinding) {
-		if (type == null) {
+		return getBindConstructor(type, false, isNestedConstructorBinding);
+	}
+
+	private Constructor<?> getBindConstructor(Class<?> type, boolean hasExistingValue,
+			boolean isNestedConstructorBinding) {
+		if (type == null || hasExistingValue) {
 			return null;
 		}
 		Constructors constructors = Constructors.getConstructors(type);

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -1113,6 +1113,14 @@ class ConfigurationPropertiesTests {
 		assertThat(bean.getItem().getValue()).isEqualTo("foo");
 	}
 
+	@Test // gh-33710
+	void loadWhenConstructorUsedInBeanMethodAndNotAsConstructorBinding() {
+		load(ConstructorUsedInBeanMethodConfiguration.class, "test.two=bound-2");
+		ConstructorUsedInBeanMethod bean = this.context.getBean(ConstructorUsedInBeanMethod.class);
+		assertThat(bean.getOne()).isEqualTo("bean-method-1");
+		assertThat(bean.getTwo()).isEqualTo("bound-2");
+	}
+
 	private AnnotationConfigApplicationContext load(Class<?> configuration, String... inlinedProperties) {
 		return load(new Class<?>[] { configuration }, inlinedProperties);
 	}
@@ -2847,4 +2855,45 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties
+	static class ConstructorUsedInBeanMethodConfiguration {
+
+		@Bean
+		@ConfigurationProperties("test")
+		ConstructorUsedInBeanMethod constructorUsedInBeanMethod() {
+			return new ConstructorUsedInBeanMethod("bean-method-1", "bean-method-2");
+		}
+
+	}
+
+	static class ConstructorUsedInBeanMethod {
+
+		private String one;
+
+		private String two;
+
+		ConstructorUsedInBeanMethod(String one, String two) {
+			this.one = one;
+			this.two = two;
+		}
+
+		String getOne() {
+			return this.one;
+		}
+
+		void setOne(String one) {
+			this.one = one;
+		}
+
+		String getTwo() {
+			return this.two;
+		}
+
+		void setTwo(String two) {
+			this.two = two;
+		}
+
+	}
+
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2022 the original author or authors.
+ * Copyright 2012-2023 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.
@@ -110,6 +110,14 @@ class DefaultBindConstructorProviderTests {
 		}
 	}
 
+	@Test
+	void getBindConstructorWhenHasExistingValueReturnsNull() {
+		OneConstructorWithConstructorBinding existingValue = new OneConstructorWithConstructorBinding("name", 123);
+		Bindable<?> bindable = Bindable.of(OneConstructorWithConstructorBinding.class).withExistingValue(existingValue);
+		Constructor<?> bindConstructor = this.provider.getBindConstructor(bindable, false);
+		assertThat(bindConstructor).isNull();
+	}
+
 	static class OnlyDefaultConstructor {
 
 	}