ConfigurationClassParser avoids ImportBeanDefinitionRegistrar double scan

Issue: SPR-12334

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

@@ -23,6 +23,7 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
+import java.util.HashSet;
 import java.util.Iterator;
 import java.util.LinkedHashSet;
 import java.util.Map;
@@ -100,6 +101,8 @@ class ConfigurationClassParser {
 
 	private final ImportStack importStack = new ImportStack();
 
+	private final Set<Class<?>> importBeanDefinitionRegistrars = new HashSet<Class<?>>();
+
 
 	/**
 	 * Create a new {@link ConfigurationClassParser} instance that will be used
@@ -370,25 +373,32 @@ class ConfigurationClassParser {
 					Object candidateToCheck = (candidate instanceof Class ? (Class) candidate :
 							this.metadataReaderFactory.getMetadataReader((String) candidate));
 					if (checkAssignability(ImportSelector.class, candidateToCheck)) {
-						// the candidate class is an ImportSelector -> delegate to it to determine imports
+						// Candidate class is an ImportSelector -> delegate to it to determine imports
 						Class<?> candidateClass = (candidate instanceof Class ? (Class) candidate :
 								this.resourceLoader.getClassLoader().loadClass((String) candidate));
 						ImportSelector selector = BeanUtils.instantiateClass(candidateClass, ImportSelector.class);
 						processImport(configClass, metadata, Arrays.asList(selector.selectImports(metadata)), false);
 					}
 					else if (checkAssignability(ImportBeanDefinitionRegistrar.class, candidateToCheck)) {
-						// the candidate class is an ImportBeanDefinitionRegistrar -> delegate to it to register additional bean definitions
+						// Candidate class is an ImportBeanDefinitionRegistrar ->
+						// delegate to it to register additional bean definitions
 						Class<?> candidateClass = (candidate instanceof Class ? (Class) candidate :
 								this.resourceLoader.getClassLoader().loadClass((String) candidate));
-						ImportBeanDefinitionRegistrar registrar = BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
-						invokeAwareMethods(registrar);
-						registrar.registerBeanDefinitions(metadata, this.registry);
+						if (!this.importBeanDefinitionRegistrars.contains(candidateClass)) {
+							ImportBeanDefinitionRegistrar registrar =
+									BeanUtils.instantiateClass(candidateClass, ImportBeanDefinitionRegistrar.class);
+							invokeAwareMethods(registrar);
+							registrar.registerBeanDefinitions(metadata, this.registry);
+							this.importBeanDefinitionRegistrars.add(candidateClass);
+						}
 					}
 					else {
-						// candidate class not an ImportSelector or ImportBeanDefinitionRegistrar -> process it as a @Configuration class
+						// Candidate class not an ImportSelector or ImportBeanDefinitionRegistrar ->
+						// process it as a @Configuration class
 						this.importStack.registerImport(metadata,
 								(candidate instanceof Class ? ((Class) candidate).getName() : (String) candidate));
-						processConfigurationClass(candidateToCheck instanceof Class ? new ConfigurationClass((Class) candidateToCheck, true) :
+						processConfigurationClass(candidateToCheck instanceof Class ?
+								new ConfigurationClass((Class) candidateToCheck, true) :
 								new ConfigurationClass((MetadataReader) candidateToCheck, true));
 					}
 				}

spring-context/src/test/java/org/springframework/context/annotation/spr12334/Spr12334Tests.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright 2002-2014 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 org.springframework.context.annotation.spr12334;
+
+import org.junit.Test;
+
+import org.springframework.beans.factory.support.BeanDefinitionRegistry;
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
+import org.springframework.core.type.AnnotationMetadata;
+
+/**
+ * @author Juergen Hoeller
+ * @author Alex Pogrebnyak
+ */
+public class Spr12334Tests {
+
+	@Test
+	public void shouldNotScanTwice() {
+		TestImport.scanned = false;
+
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
+		context.scan(TestImport.class.getPackage().getName());
+		context.refresh();
+		context.getBean(TestConfiguration.class);
+	}
+
+
+	@Import(TestImport.class)
+	public @interface AnotherImport {
+	}
+
+
+	@Configuration
+	@AnotherImport
+	public static class TestConfiguration {
+	}
+
+
+	public static class TestImport implements ImportBeanDefinitionRegistrar {
+
+		private static boolean scanned = false;
+
+		@Override
+		public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry)  {
+			if (scanned) {
+				throw new IllegalStateException("Already scanned");
+			}
+			scanned = true;
+		}
+	}
+
+}