@Bean definitions override scanned classes, plus check whether overriding is actually allowed

Issue: SPR-9567
Issue: SPR-9682

spring-context/src/main/java/org/springframework/context/annotation/ConfigurationClassBeanDefinitionReader.java

@@ -27,6 +27,7 @@ import java.util.Set;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 
+import org.springframework.beans.factory.BeanDefinitionStoreException;
 import org.springframework.beans.factory.annotation.AnnotatedBeanDefinition;
 import org.springframework.beans.factory.annotation.AnnotatedGenericBeanDefinition;
 import org.springframework.beans.factory.annotation.Autowire;
@@ -42,6 +43,7 @@ import org.springframework.beans.factory.support.AbstractBeanDefinitionReader;
 import org.springframework.beans.factory.support.BeanDefinitionReader;
 import org.springframework.beans.factory.support.BeanDefinitionRegistry;
 import org.springframework.beans.factory.support.BeanNameGenerator;
+import org.springframework.beans.factory.support.DefaultListableBeanFactory;
 import org.springframework.beans.factory.support.RootBeanDefinition;
 import org.springframework.beans.factory.xml.XmlBeanDefinitionReader;
 import org.springframework.context.annotation.ConfigurationCondition.ConfigurationPhase;
@@ -287,6 +289,12 @@ class ConfigurationClassBeanDefinitionReader {
 			return (ccbd.getMetadata().getClassName().equals(beanMethod.getConfigurationClass().getMetadata().getClassName()));
 		}
 
+		// A bean definition resulting from a component scan can be silently overridden
+		// by an @Bean method, as of 4.2...
+		if (existingBeanDef instanceof ScannedGenericBeanDefinition) {
+			return false;
+		}
+
 		// Has the existing bean definition bean marked as a framework-generated bean?
 		// -> allow the current bean method to override it, since it is application-level
 		if (existingBeanDef.getRole() > BeanDefinition.ROLE_APPLICATION) {
@@ -295,6 +303,11 @@ class ConfigurationClassBeanDefinitionReader {
 
 		// At this point, it's a top-level override (probably XML), just having been parsed
 		// before configuration class processing kicks in...
+		if (this.registry instanceof DefaultListableBeanFactory &&
+				!((DefaultListableBeanFactory) this.registry).isAllowBeanDefinitionOverriding()) {
+			throw new BeanDefinitionStoreException(beanMethod.getConfigurationClass().getResource().getDescription(),
+					beanName, "@Bean definition illegally overridden by existing bean definition: " + existingBeanDef);
+		}
 		if (logger.isInfoEnabled()) {
 			logger.info(String.format("Skipping bean definition for %s: a definition for bean '%s' " +
 					"already exists. This top-level bean definition is considered as an override.",

spring-context/src/test/java/example/scannable_implicitbasepackage/ComponentScanAnnotatedConfigWithImplicitBasePackage.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -13,8 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package example.scannable_implicitbasepackage;
 
+import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.context.annotation.Configuration;
 
@@ -24,4 +26,10 @@ import org.springframework.context.annotation.Configuration;
 @Configuration
 @ComponentScan
 public class ComponentScanAnnotatedConfigWithImplicitBasePackage {
+
+	@Bean  // override of scanned class
+	public ConfigurableComponent configurableComponent() {
+		return new ConfigurableComponent(true);
+	}
+
 }

spring-context/src/test/java/example/scannable_implicitbasepackage/ConfigurableComponent.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2002-2015 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
+ *
+ *      http://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 example.scannable_implicitbasepackage;
+
+import org.springframework.stereotype.Component;
+
+/**
+ * @author Juergen Hoeller
+ */
+@Component
+public class ConfigurableComponent {
+
+	private final boolean flag;
+
+	public ConfigurableComponent() {
+		this(false);
+	}
+
+	public ConfigurableComponent(boolean flag) {
+		this.flag = flag;
+	}
+
+	public boolean isFlag() {
+		return this.flag;
+	}
+
+}

spring-context/src/test/java/example/scannable_implicitbasepackage/ScannedComponent.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -13,6 +13,7 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 package example.scannable_implicitbasepackage;
 
 import org.springframework.stereotype.Component;

spring-context/src/test/java/org/springframework/context/annotation/ComponentScanAnnotationIntegrationTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2014 the original author or authors.
+ * Copyright 2002-2015 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.
@@ -30,6 +30,7 @@ import example.scannable.FooService;
 import example.scannable.MessageBean;
 import example.scannable.ScopedProxyTestBean;
 import example.scannable_implicitbasepackage.ComponentScanAnnotatedConfigWithImplicitBasePackage;
+import example.scannable_implicitbasepackage.ConfigurableComponent;
 import example.scannable_scoped.CustomScopeAnnotationBean;
 import example.scannable_scoped.MyScope;
 import org.junit.Test;
@@ -107,6 +108,7 @@ public class ComponentScanAnnotationIntegrationTests {
 		assertThat("@ComponentScan annotated @Configuration class registered directly against " +
 				"AnnotationConfigApplicationContext did not trigger component scanning as expected",
 				ctx.containsBean("scannedComponent"), is(true));
+		assertThat("@Bean method overrides scanned class", ctx.getBean(ConfigurableComponent.class).isFlag(), is(true));
 	}
 
 	@Test