abstractbeanfactory.java

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	 * Check the given merged bean definition,
	 * potentially throwing validation exceptions.
	 * @param mbd the merged bean definition to check
	 * @param beanName the name of the bean
	 * @param args the arguments for bean creation, if any
	 * @throws BeanDefinitionStoreException in case of validation failure
	 */
	protected void checkMergedBeanDefinition(RootBeanDefinition mbd, String beanName, Object[] args)
			throws BeanDefinitionStoreException {

		// check if bean definition is not abstract
		if (mbd.isAbstract()) {
			throw new BeanIsAbstractException(beanName);
		}

		// Check validity of the usage of the args parameter. This can
		// only be used for prototypes constructed via a factory method.
		if (args != null && !mbd.isPrototype()) {
			throw new BeanDefinitionStoreException(
					"Can only specify arguments for the getBean method when referring to a prototype bean definition");
		}
	}

	/**
	 * Remove the merged bean definition for the specified bean,
	 * recreating it on next access.
	 * @param beanName the bean name to clear the merged definition for
	 */
	protected void clearMergedBeanDefinition(String beanName) {
		this.mergedBeanDefinitions.remove(beanName);
	}

	/**
	 * Resolve the bean class for the specified bean definition,
	 * resolving a bean class name into a Class reference (if necessary)
	 * and storing the resolved Class in the bean definition for further use.
	 * @param mbd the merged bean definition to determine the class for
	 * @param beanName the name of the bean (for error handling purposes)
	 * @return the resolved bean class (or <code>null</code> if none)
	 * @throws CannotLoadBeanClassException if we failed to load the class
	 */
	protected Class resolveBeanClass(RootBeanDefinition mbd, String beanName) {
		return resolveBeanClass(mbd, beanName, null);
	}

	/**
	 * Resolve the bean class for the specified bean definition,
	 * resolving a bean class name into a Class reference (if necessary)
	 * and storing the resolved Class in the bean definition for further use.
	 * @param mbd the merged bean definition to determine the class for
	 * @param beanName the name of the bean (for error handling purposes)
	 * @param typesToMatch the types to match in case of internal type matching purposes
	 * (also signals that the returned <code>Class</code> will never be exposed to application code)
	 * @return the resolved bean class (or <code>null</code> if none)
	 * @throws CannotLoadBeanClassException if we failed to load the class
	 */
	protected Class resolveBeanClass(RootBeanDefinition mbd, String beanName, Class[] typesToMatch)
			throws CannotLoadBeanClassException {
		try {
			if (mbd.hasBeanClass()) {
				return mbd.getBeanClass();
			}
			if (typesToMatch != null) {
				ClassLoader tempClassLoader = getTempClassLoader();
				if (tempClassLoader != null) {
					if (tempClassLoader instanceof DecoratingClassLoader) {
						DecoratingClassLoader dcl = (DecoratingClassLoader) tempClassLoader;
						for (int i = 0; i < typesToMatch.length; i++) {
							dcl.excludeClass(typesToMatch[i].getName());
						}
					}
					String className = mbd.getBeanClassName();
					return (className != null ? ClassUtils.forName(className, tempClassLoader) : null);
				}
			}
			return mbd.resolveBeanClass(getBeanClassLoader());
		}
		catch (ClassNotFoundException ex) {
			throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), ex);
		}
		catch (LinkageError err) {
			throw new CannotLoadBeanClassException(mbd.getResourceDescription(), beanName, mbd.getBeanClassName(), err);
		}
	}


	/**
	 * Predict the eventual bean type (of the processed bean instance) for the
	 * specified bean. Called by {@link #getType} and {@link #isTypeMatch}.
	 * Does not need to handle FactoryBeans specifically, since it is only
	 * supposed to operate on the raw bean type.
	 * <p>This implementation is simplistic in that it is not able to
	 * handle factory methods and InstantiationAwareBeanPostProcessors.
	 * It only predicts the bean type correctly for a standard bean.
	 * To be overridden in subclasses, applying more sophisticated type detection.
	 * @param beanName the name of the bean
	 * @param mbd the merged bean definition to determine the type for
	 * @param typesToMatch the types to match in case of internal type matching purposes
	 * (also signals that the returned <code>Class</code> will never be exposed to application code)
	 * @return the type of the bean, or <code>null</code> if not predictable
	 */
	protected Class predictBeanType(String beanName, RootBeanDefinition mbd, Class[] typesToMatch) {
		if (mbd.getFactoryMethodName() != null) {
			return null;
		}
		return resolveBeanClass(mbd, beanName, typesToMatch);
	}

	/**
	 * Check whether the given bean is defined as a {@link FactoryBean}.
	 * @param beanName the name of the bean
	 * @param mbd the corresponding bean definition
	 */
	protected boolean isFactoryBean(String beanName, RootBeanDefinition mbd) {
		Class beanClass = predictBeanType(beanName, mbd, new Class[] {FactoryBean.class});
		return (beanClass != null && FactoryBean.class.isAssignableFrom(beanClass));
	}

	/**
	 * Determine the bean type for the given FactoryBean definition, as far as possible.
	 * Only called if there is no singleton instance registered for the target bean already.
	 * <p>The default implementation creates the FactoryBean via <code>getBean</code>
	 * to call its <code>getObjectType</code> method. Subclasses are encouraged to optimize
	 * this, typically by just instantiating the FactoryBean but not populating it yet,
	 * trying whether its <code>getObjectType</code> method already returns a type.
	 * If no type found, a full FactoryBean creation as performed by this implementation
	 * should be used as fallback.
	 * @param beanName the name of the bean
	 * @param mbd the merged bean definition for the bean
	 * @return the type for the bean if determinable, or <code>null</code> else
	 * @see org.springframework.beans.factory.FactoryBean#getObjectType()
	 * @see #getBean(String)
	 */
	protected Class getTypeForFactoryBean(String beanName, RootBeanDefinition mbd) {
		if (!mbd.isSingleton()) {
			return null;
		}
		try {
			FactoryBean factoryBean =
					(FactoryBean) doGetBean(FACTORY_BEAN_PREFIX + beanName, FactoryBean.class, null, true);
			return getTypeForFactoryBean(factoryBean);
		}
		catch (BeanCreationException ex) {
			// Can only happen when getting a FactoryBean.
			if (logger.isDebugEnabled()) {
				logger.debug("Ignoring bean creation exception on FactoryBean type check: " + ex);
			}
			onSuppressedException(ex);
			return null;
		}
	}

	/**
	 * Mark the specified bean as already created (or about to be created).
	 * <p>This allows the bean factory to optimize its caching for repeated
	 * creation of the specified bean.
	 * @param beanName the name of the bean
	 */
	protected void markBeanAsCreated(String beanName) {
		this.alreadyCreated.add(beanName);
	}

	/**
	 * Determine whether the specified bean is eligible for having
	 * its bean definition metadata cached.
	 * @param beanName the name of the bean
	 * @return <code>true</code> if the bean's metadata may be cached
	 * at this point already
	 */
	protected boolean isBeanEligibleForMetadataCaching(String beanName) {
		return this.alreadyCreated.contains(beanName);
	}

	/**
	 * Remove the singleton instance (if any) for the given bean name,
	 * but only if it hasn't been used for other purposes than type checking.
	 * @param beanName the name of the bean
	 * @return <code>true</code> if actually removed, <code>false</code> otherwise
	 */
	protected boolean removeSingletonIfCreatedForTypeCheckOnly(String beanName) {
		if (!this.alreadyCreated.contains(beanName)) {
			removeSingleton(beanName);
			return true;
		}
		else {
			return false;
		}
	}

	/**
	 * Get the object for the given bean instance, either the bean
	 * instance itself or its created object in case of a FactoryBean.
	 * @param beanInstance the shared bean instance
	 * @param name name that may include factory dereference prefix
	 * @param beanName the canonical bean name
	 * @param mbd the merged bean definition
	 * @return the object to expose for the bean
	 */
	protected Object getObjectForBeanInstance(
			Object beanInstance, String name, String beanName, RootBeanDefinition mbd) {

		// Don't let calling code try to dereference the factory if the bean isn't a factory.
		if (BeanFactoryUtils.isFactoryDereference(name) && !(beanInstance instanceof FactoryBean)) {
			throw new BeanIsNotAFactoryException(transformedBeanName(name), beanInstance.getClass());
		}

		// Now we have the bean instance, which may be a normal bean or a FactoryBean.
		// If it's a FactoryBean, we use it to create a bean instance, unless the
		// caller actually wants a reference to the factory.
		if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
			return beanInstance;
		}

		Object object = null;
		if (mbd == null) {
			object = getCachedObjectForFactoryBean(beanName);
		}
		if (object == null) {
			// Return bean instance from factory.
			FactoryBean factory = (FactoryBean) beanInstance;
			// Caches object obtained from FactoryBean if it is a singleton.
			if (mbd == null && containsBeanDefinition(beanName)) {
				mbd = getMergedLocalBeanDefinition(beanName);
			}
			boolean synthetic = (mbd != null && mbd.isSynthetic());
			object = getObjectFromFactoryBean(factory, beanName, !synthetic);
		}
		return object;
	}

	/**
	 * Determine whether the given bean name is already in use within this factory,
	 * i.e. whether there is a local bean or alias registered under this name or
	 * an inner bean created with this name.
	 * @param beanName the name to check
	 */
	public boolean isBeanNameInUse(String beanName) {
		return isAlias(beanName) || containsLocalBean(beanName) || hasDependentBean(beanName);
	}

	/**
	 * Determine whether the given bean requires destruction on shutdown.
	 * <p>The default implementation checks the DisposableBean interface as well as
	 * a specified destroy method and registered DestructionAwareBeanPostProcessors.
	 * @param bean the bean instance to check
	 * @param mbd the corresponding bean definition
	 * @see org.springframework.beans.factory.DisposableBean
	 * @see AbstractBeanDefinition#getDestroyMethodName()
	 * @see org.springframework.beans.factory.config.DestructionAwareBeanPostProcessor
	 */
	protected boolean requiresDestruction(Object bean, RootBeanDefinition mbd) {
		return (bean instanceof DisposableBean || mbd.getDestroyMethodName() != null ||
				hasDestructionAwareBeanPostProcessors());
	}

	/**
	 * Add the given bean to the list of disposable beans in this factory,
	 * registering its DisposableBean interface and/or the given destroy method
	 * to be called on factory shutdown (if applicable). Only applies to singletons.
	 * @param beanName the name of the bean
	 * @param bean the bean instance
	 * @param mbd the bean definition for the bean
	 * @see RootBeanDefinition#isSingleton
	 * @see RootBeanDefinition#getDependsOn
	 * @see #registerDisposableBean
	 * @see #registerDependentBean
	 */
	protected void registerDisposableBeanIfNecessary(String beanName, Object bean, RootBeanDefinition mbd) {
		if (!mbd.isPrototype() && requiresDestruction(bean, mbd)) {
			if (mbd.isSingleton()) {
				// Register a DisposableBean implementation that performs all destruction
				// work for the given bean: DestructionAwareBeanPostProcessors,
				// DisposableBean interface, custom destroy method.
				registerDisposableBean(beanName,
						new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors()));
			}
			else {
				// A bean with a custom scope...
				Scope scope = (Scope) this.scopes.get(mbd.getScope());
				if (scope == null) {
					throw new IllegalStateException("No Scope registered for scope '" + mbd.getScope() + "'");
				}
				scope.registerDestructionCallback(beanName,
						new DisposableBeanAdapter(bean, beanName, mbd, getBeanPostProcessors()));
			}
		}
	}


	//---------------------------------------------------------------------
	// Abstract methods to be implemented by subclasses
	//---------------------------------------------------------------------

	/**
	 * Check if this bean factory contains a bean definition with the given name.
	 * Does not consider any hierarchy this factory may participate in.
	 * Invoked by <code>containsBean</code> when no cached singleton instance is found.
	 * <p>Depending on the nature of the concrete bean factory implementation,
	 * this operation might be expensive (for example, because of directory lookups
	 * in external registries). However, for listable bean factories, this usually
	 * just amounts to a local hash lookup: The operation is therefore part of the
	 * public interface there. The same implementation can serve for both this
	 * template method and the public interface method in that case.
	 * @param beanName the name of the bean to look for
	 * @return if this bean factory contains a bean definition with the given name
	 * @see #containsBean
	 * @see org.springframework.beans.factory.ListableBeanFactory#containsBeanDefinition
	 */
	protected abstract boolean containsBeanDefinition(String beanName);

	/**
	 * Return the bean definition for the given bean name.
	 * Subclasses should normally implement caching, as this method is invoked
	 * by this class every time bean definition metadata is needed.
	 * <p>Depending on the nature of the concrete bean factory implementation,
	 * this operation might be expensive (for example, because of directory lookups
	 * in external registries). However, for listable bean factories, this usually
	 * just amounts to a local hash lookup: The operation is therefore part of the
	 * public interface there. The same implementation can serve for both this
	 * template method and the public interface method in that case.
	 * @param beanName the name of the bean to find a definition for
	 * @return the BeanDefinition for this prototype name (never <code>null</code>)
	 * @throws org.springframework.beans.factory.NoSuchBeanDefinitionException
	 * if the bean definition cannot be resolved
	 * @throws BeansException in case of errors
	 * @see RootBeanDefinition
	 * @see ChildBeanDefinition
	 * @see org.springframework.beans.factory.config.ConfigurableListableBeanFactory#getBeanDefinition
	 */
	protected abstract BeanDefinition getBeanDefinition(String beanName) throws BeansException;

	/**
	 * Create a bean instance for the given bean definition.
	 * The bean definition will already have been merged with the parent
	 * definition in case of a child definition.
	 * <p>All the other methods in this class invoke this method, although
	 * beans may be cached after being instantiated by this method. All bean
	 * instantiation within this class is performed by this method.
	 * @param beanName the name of the bean
	 * @param mbd the merged bean definition for the bean
	 * @param args arguments to use if creating a prototype using explicit arguments to a
	 * static factory method. This parameter must be <code>null</code> except in this case.
	 * @return a new instance of the bean
	 * @throws BeanCreationException if the bean could not be created
	 */
	protected abstract Object createBean(String beanName, RootBeanDefinition mbd, Object[] args)
			throws BeanCreationException;

}