Validate @ConfigurationProperties bean definitions

Add a bean definition post-processor that throws a better exception
if @ConstructorBinding property beans are being instantiated as
regular Spring beans.

Prior to this commit, a constructor bound properties bean would fail
with an unsatisfied dependency exception which isn't all that helpful.

Closes gh-17831

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

@@ -0,0 +1,81 @@
+/*
+ * Copyright 2012-2019 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.springframework.beans.BeansException;
+import org.springframework.beans.factory.BeanCreationException;
+import org.springframework.beans.factory.config.BeanDefinition;
+import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.beans.factory.support.GenericBeanDefinition;
+import org.springframework.boot.context.properties.ConfigurationPropertiesBean.BindMethod;
+import org.springframework.core.Ordered;
+import org.springframework.util.Assert;
+
+/**
+ * {@link BeanFactoryPostProcessor} to validate that regular bean definitions aren't
+ * creating {@link ConstructorBinding} beans.
+ *
+ * @author Phillip Webb
+ */
+class ConfigurationPropertiesBeanDefinitionValidator implements BeanFactoryPostProcessor, Ordered {
+
+	private static final String BEAN_NAME = ConfigurationPropertiesBeanDefinitionValidator.class.getName();
+
+	@Override
+	public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
+		for (String beanName : beanFactory.getBeanDefinitionNames()) {
+			BeanDefinition definition = beanFactory.getBeanDefinition(beanName);
+			if (!(definition instanceof ConfigurationPropertiesValueObjectBeanDefinition)) {
+				validate(beanFactory, beanName);
+			}
+		}
+	}
+
+	@Override
+	public int getOrder() {
+		return Ordered.LOWEST_PRECEDENCE;
+	}
+
+	private void validate(ConfigurableListableBeanFactory beanFactory, String beanName) {
+		Class<?> beanClass = beanFactory.getType(beanName, false);
+		System.out.println(beanName);
+		if (beanClass != null && BindMethod.forClass(beanClass) == BindMethod.VALUE_OBJECT) {
+			throw new BeanCreationException(beanName,
+					"@EnableConfigurationProperties or @ConfigurationPropertiesScan must be used to add "
+							+ "@ConstructorBinding type " + beanClass.getName());
+		}
+	}
+
+	/**
+	 * Register a {@link ConfigurationPropertiesBeanDefinitionValidator} bean if one is
+	 * not already registered.
+	 * @param registry the bean definition registry
+	 */
+	static void register(BeanDefinitionRegistry registry) {
+		Assert.notNull(registry, "Registry must not be null");
+		if (!registry.containsBeanDefinition(BEAN_NAME)) {
+			GenericBeanDefinition definition = new GenericBeanDefinition();
+			definition.setBeanClass(ConfigurationPropertiesBeanDefinitionValidator.class);
+			definition.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);
+			registry.registerBeanDefinition(BEAN_NAME, definition);
+		}
+		ConfigurationPropertiesBinder.register(registry);
+	}
+
+}

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

@@ -49,6 +49,7 @@ class EnableConfigurationPropertiesRegistrar implements ImportBeanDefinitionRegi
 	@SuppressWarnings("deprecation")
 	static void registerInfrastructureBeans(BeanDefinitionRegistry registry) {
 		ConfigurationPropertiesBindingPostProcessor.register(registry);
+		ConfigurationPropertiesBeanDefinitionValidator.register(registry);
 		ConfigurationBeanFactoryMetadata.register(registry);
 	}
 

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

@@ -55,6 +55,7 @@ import org.springframework.boot.testsupport.system.OutputCaptureExtension;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.ImportResource;
 import org.springframework.context.annotation.Scope;
 import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
@@ -758,6 +759,13 @@ class ConfigurationPropertiesTests {
 		assertThat(bean.getBar()).isEqualTo(5);
 	}
 
+	@Test // gh-17831
+	void loadWhenBindingConstructorParametersViaImportShouldThrowException() {
+		assertThatExceptionOfType(BeanCreationException.class)
+				.isThrownBy(() -> load(ImportConstructorParameterPropertiesConfiguration.class))
+				.withMessageContaining("@EnableConfigurationProperties or @ConfigurationPropertiesScan must be used");
+	}
+
 	@Test
 	void loadWhenBindingToConstructorParametersWithDefaultValuesShouldBind() {
 		load(ConstructorParameterConfiguration.class);
@@ -1797,6 +1805,13 @@ class ConfigurationPropertiesTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	@EnableConfigurationProperties
+	@Import(ConstructorParameterProperties.class)
+	static class ImportConstructorParameterPropertiesConfiguration {
+
+	}
+
 	@ImmutableConfigurationProperties(prefix = "test")
 	@Validated
 	static class ConstructorParameterValidatedProperties {