Bean class name may contain SpEL expression for late resolution

Issue: SPR-12817

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.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.
@@ -443,37 +443,43 @@ public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFac
 	 * @see #doCreateBean
 	 */
 	@Override
-	protected Object createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
-			throws BeanCreationException {
-
+	protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
 		if (logger.isDebugEnabled()) {
 			logger.debug("Creating instance of bean '" + beanName + "'");
 		}
-		// Make sure bean class is actually resolved at this point.
-		resolveBeanClass(mbd, beanName);
+		RootBeanDefinition mbdToUse = mbd;
+
+		// Make sure bean class is actually resolved at this point, and
+		// clone the bean definition in case of a dynamically resolved Class
+		// which cannot be stored in the shared merged bean definition.
+		Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
+		if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
+			mbdToUse = new RootBeanDefinition(mbd);
+			mbdToUse.setBeanClass(resolvedClass);
+		}
 
 		// Prepare method overrides.
 		try {
-			mbd.prepareMethodOverrides();
+			mbdToUse.prepareMethodOverrides();
 		}
 		catch (BeanDefinitionValidationException ex) {
-			throw new BeanDefinitionStoreException(mbd.getResourceDescription(),
+			throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
 					beanName, "Validation of method overrides failed", ex);
 		}
 
 		try {
 			// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
-			Object bean = resolveBeforeInstantiation(beanName, mbd);
+			Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
 			if (bean != null) {
 				return bean;
 			}
 		}
 		catch (Throwable ex) {
-			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
+			throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
 					"BeanPostProcessor before instantiation of bean failed", ex);
 		}
 
-		Object beanInstance = doCreateBean(beanName, mbd, args);
+		Object beanInstance = doCreateBean(beanName, mbdToUse, args);
 		if (logger.isDebugEnabled()) {
 			logger.debug("Finished creating instance of bean '" + beanName + "'");
 		}
@@ -833,8 +839,7 @@ public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFac
 
 	/**
 	 * Obtain a "shortcut" singleton FactoryBean instance to use for a
-	 * {@code getObjectType()} call, without full initialization
-	 * of the FactoryBean.
+	 * {@code getObjectType()} call, without full initialization of the FactoryBean.
 	 * @param beanName the name of the bean
 	 * @param mbd the bean definition for the bean
 	 * @return the FactoryBean instance, or {@code null} to indicate
@@ -875,8 +880,7 @@ public abstract class AbstractAutowireCapableBeanFactory extends AbstractBeanFac
 
 	/**
 	 * Obtain a "shortcut" non-singleton FactoryBean instance to use for a
-	 * {@code getObjectType()} call, without full initialization
-	 * of the FactoryBean.
+	 * {@code getObjectType()} call, without full initialization of the FactoryBean.
 	 * @param beanName the name of the bean
 	 * @param mbd the bean definition for the bean
 	 * @return the FactoryBean instance, or {@code null} to indicate

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractBeanFactory.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.
@@ -1333,20 +1333,44 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	}
 
 	private Class<?> doResolveBeanClass(RootBeanDefinition mbd, Class<?>... typesToMatch) throws ClassNotFoundException {
+		ClassLoader beanClassLoader = getBeanClassLoader();
+		ClassLoader classLoaderToUse = beanClassLoader;
 		if (!ObjectUtils.isEmpty(typesToMatch)) {
+			// When just doing type checks (i.e. not creating an actual instance yet),
+			// use the specified temporary class loader (e.g. in a weaving scenario).
 			ClassLoader tempClassLoader = getTempClassLoader();
 			if (tempClassLoader != null) {
+				classLoaderToUse = tempClassLoader;
 				if (tempClassLoader instanceof DecoratingClassLoader) {
 					DecoratingClassLoader dcl = (DecoratingClassLoader) tempClassLoader;
 					for (Class<?> typeToMatch : typesToMatch) {
 						dcl.excludeClass(typeToMatch.getName());
 					}
 				}
-				String className = mbd.getBeanClassName();
-				return (className != null ? ClassUtils.forName(className, tempClassLoader) : null);
 			}
 		}
-		return mbd.resolveBeanClass(getBeanClassLoader());
+		String className = mbd.getBeanClassName();
+		if (className != null) {
+			Object evaluated = evaluateBeanDefinitionString(className, mbd);
+			if (!className.equals(evaluated)) {
+				// A dynamically resolved expression, supported as of 4.2...
+				if (evaluated instanceof Class) {
+					return (Class<?>) evaluated;
+				}
+				else if (evaluated instanceof String) {
+					return ClassUtils.forName((String) evaluated, classLoaderToUse);
+				}
+				else {
+					throw new IllegalStateException("Invalid class name expression result: " + evaluated);
+				}
+			}
+			// When resolving against a temporary class loader, exit early in order
+			// to avoid storing the resolved Class in the bean definition.
+			if (classLoaderToUse != beanClassLoader) {
+				return ClassUtils.forName(className, classLoaderToUse);
+			}
+		}
+		return mbd.resolveBeanClass(beanClassLoader);
 	}
 
 	/**

spring-context/src/test/java/org/springframework/context/expression/ApplicationContextExpressionTests.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.
@@ -101,14 +101,14 @@ public class ApplicationContextExpressionTests {
 		ac.registerBeanDefinition("tb0", bd0);
 
 		GenericBeanDefinition bd1 = new GenericBeanDefinition();
-		bd1.setBeanClass(TestBean.class);
+		bd1.setBeanClassName("#{tb0.class}");
 		bd1.setScope("myScope");
 		bd1.getConstructorArgumentValues().addGenericArgumentValue("XXX#{tb0.name}YYY#{mySpecialAttr}ZZZ");
 		bd1.getConstructorArgumentValues().addGenericArgumentValue("#{mySpecialAttr}");
 		ac.registerBeanDefinition("tb1", bd1);
 
 		GenericBeanDefinition bd2 = new GenericBeanDefinition();
-		bd2.setBeanClass(TestBean.class);
+		bd2.setBeanClassName("#{tb1.class.name}");
 		bd2.setScope("myScope");
 		bd2.getPropertyValues().add("name", "{ XXX#{tb0.name}YYY#{mySpecialAttr}ZZZ }");
 		bd2.getPropertyValues().add("age", "#{mySpecialAttr}");