Reuse `ConfigurationProperties` bean defined in parent

This commit makes sure that if a `ConfigurationProperties` annotated bean
already exists in the parent context, a new one is not created in the
child anymore.

This makes sure that a single bean exists in a parent/child hierarchy if
`@EnableConfigurationProperties` is processed in both context on the same
class.

Closes gh-8187

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2016 the original author or authors.
+ * Copyright 2012-2017 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 java.util.ArrayList;
 import java.util.List;
 
+import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.support.AbstractBeanDefinition;
 import org.springframework.beans.factory.support.BeanDefinitionBuilder;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
@@ -78,7 +79,8 @@ class EnableConfigurationPropertiesImportSelector implements ImportSelector {
 				String prefix = extractPrefix(type);
 				String name = (StringUtils.hasText(prefix) ? prefix + "-" + type.getName()
 						: type.getName());
-				if (!registry.containsBeanDefinition(name)) {
+				if (!containsBeanDefinition(
+						(ConfigurableListableBeanFactory) registry, name)) {
 					registerBeanDefinition(registry, type, name);
 				}
 			}
@@ -119,6 +121,23 @@ class EnableConfigurationPropertiesImportSelector implements ImportSelector {
 							+ " annotation found on  '" + type.getName() + "'.");
 		}
 
+		private boolean containsBeanDefinition(
+				ConfigurableListableBeanFactory beanFactory, String name) {
+
+			boolean result = beanFactory.containsBeanDefinition(name);
+			if (result) {
+				return true;
+			}
+			if (beanFactory
+					.getParentBeanFactory() instanceof ConfigurableListableBeanFactory) {
+				return containsBeanDefinition(
+						(ConfigurableListableBeanFactory) beanFactory
+								.getParentBeanFactory(),
+						name);
+			}
+			return false;
+		}
+
 	}
 
 }

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

@@ -290,18 +290,24 @@ public class EnableConfigurationPropertiesTests {
 
 	@Test
 	public void testBindingWithParentContext() {
-		AnnotationConfigApplicationContext parent = new AnnotationConfigApplicationContext();
+		AnnotationConfigApplicationContext parent =
+				new AnnotationConfigApplicationContext();
 		parent.register(TestConfiguration.class);
+		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(parent,
+				"name=parent");
 		parent.refresh();
-		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context,
-				"name=foo");
 		this.context.setParent(parent);
+		TestPropertySourceUtils.addInlinedPropertiesToEnvironment(this.context,
+				"name=child");
 		this.context.register(TestConfiguration.class, TestConsumer.class);
 		this.context.refresh();
 		assertThat(this.context.getBeanNamesForType(TestProperties.class).length)
+				.isEqualTo(0);
+		assertThat(parent.getBeanNamesForType(TestProperties.class).length)
 				.isEqualTo(1);
-		assertThat(parent.getBeanNamesForType(TestProperties.class).length).isEqualTo(1);
-		assertThat(this.context.getBean(TestConsumer.class).getName()).isEqualTo("foo");
+		assertThat(this.context.getBean(TestConsumer.class).getName())
+				.isEqualTo("parent");
+		parent.close();
 	}
 
 	@Test