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Spring IOC源码解析(09)BeanFactoryUtils

2020-06-11

前言

BeanFactoryUtils作为bean工厂操作的工具类,包含了很多的方法。对这些方法的理解,将加深我们后续对BeanFactory实现的分析。

源码解析

/**
 * Convenience methods operating on bean factories, in particular
 * on the {@link ListableBeanFactory} interface.
 *
 * <p>Returns bean counts, bean names or bean instances,
 * taking into account the nesting hierarchy of a bean factory
 * (which the methods defined on the ListableBeanFactory interface don't,
 * in contrast to the methods defined on the BeanFactory interface).
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Chris Beams
 * @since 04.07.2003
 */
public abstract class BeanFactoryUtils {

	/**
	 * bean名称的分隔符,当类名或父类名不是唯一时,将通过追加后缀`#1`或`#2`的方式来使得bean名称变得唯一。
	 * 通常在内部bean的时候使用。
	 * Separator for generated bean names. If a class name or parent name is not
	 * unique, "#1", "#2" etc will be appended, until the name becomes unique.
	 */
	public static final String GENERATED_BEAN_NAME_SEPARATOR = "#";

	/**
	 * 缓存map,工厂bean名称 -> 剥离掉&前缀后的bean名称
	 * 即:工厂bean创建的bean的名称
	 * Cache from name with factory bean prefix to stripped name without dereference.
	 * @since 5.1
	 * @see BeanFactory#FACTORY_BEAN_PREFIX
	 */
	private static final Map<String, String> transformedBeanNameCache = new ConcurrentHashMap<>();


	/**
	 * 根据名称判断是否是一个工厂bean的名称
	 * Return whether the given name is a factory dereference
	 * (beginning with the factory dereference prefix).
	 * @param name the name of the bean
	 * @return whether the given name is a factory dereference
	 * @see BeanFactory#FACTORY_BEAN_PREFIX
	 */
	public static boolean isFactoryDereference(@Nullable String name) {
		return (name != null && name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
	}

	/**
	 * 将带有&的所有前缀全部去掉,也就是实际工厂bean创建后的bean的名称
	 * 这儿使用了循环遍历,是因为工厂bean创建出来的bean也可能是另外一个工厂bean,以此类推
	 * Return the actual bean name, stripping out the factory dereference
	 * prefix (if any, also stripping repeated factory prefixes if found).
	 * @param name the name of the bean
	 * @return the transformed name
	 * @see BeanFactory#FACTORY_BEAN_PREFIX
	 */
	public static String transformedBeanName(String name) {
		Assert.notNull(name, "'name' must not be null");
		if (!name.startsWith(BeanFactory.FACTORY_BEAN_PREFIX)) {
			return name;
		}
		return transformedBeanNameCache.computeIfAbsent(name, beanName -> {
			do {
				beanName = beanName.substring(BeanFactory.FACTORY_BEAN_PREFIX.length());
			}
			while (beanName.startsWith(BeanFactory.FACTORY_BEAN_PREFIX));
			return beanName;
		});
	}

	/**
	 * 判断是否内部生成的bean名称
	 * Return whether the given name is a bean name which has been generated
	 * by the default naming strategy (containing a "#..." part).
	 * @param name the name of the bean
	 * @return whether the given name is a generated bean name
	 * @see #GENERATED_BEAN_NAME_SEPARATOR
	 * @see org.springframework.beans.factory.support.BeanDefinitionReaderUtils#generateBeanName
	 * @see org.springframework.beans.factory.support.DefaultBeanNameGenerator
	 */
	public static boolean isGeneratedBeanName(@Nullable String name) {
		return (name != null && name.contains(GENERATED_BEAN_NAME_SEPARATOR));
	}

	/**
	 * 获取内部bean所在的外部bean
	 * Extract the "raw" bean name from the given (potentially generated) bean name,
	 * excluding any "#..." suffixes which might have been added for uniqueness.
	 * @param name the potentially generated bean name
	 * @return the raw bean name
	 * @see #GENERATED_BEAN_NAME_SEPARATOR
	 */
	public static String originalBeanName(String name) {
		Assert.notNull(name, "'name' must not be null");
		int separatorIndex = name.indexOf(GENERATED_BEAN_NAME_SEPARATOR);
		return (separatorIndex != -1 ? name.substring(0, separatorIndex) : name);
	}


	// Retrieval of bean names

	/**
	 * 获取包含祖先在内的所有bean的数量
	 * Count all beans in any hierarchy in which this factory participates.
	 * Includes counts of ancestor bean factories.
	 * <p>Beans that are "overridden" (specified in a descendant factory
	 * with the same name) are only counted once.
	 * @param lbf the bean factory
	 * @return count of beans including those defined in ancestor factories
	 * @see #beanNamesIncludingAncestors
	 */
	public static int countBeansIncludingAncestors(ListableBeanFactory lbf) {
		return beanNamesIncludingAncestors(lbf).length;
	}

	/**
	 * 获取包含祖先在内的所有bean名称数组
	 * Return all bean names in the factory, including ancestor factories.
	 * @param lbf the bean factory
	 * @return the array of matching bean names, or an empty array if none
	 * @see #beanNamesForTypeIncludingAncestors
	 */
	public static String[] beanNamesIncludingAncestors(ListableBeanFactory lbf) {
		return beanNamesForTypeIncludingAncestors(lbf, Object.class);
	}

	/**
	 * 获取包含祖先在内的特定类型的bean名称数组
	 * Get all bean names for the given type, including those defined in ancestor
	 * factories. Will return unique names in case of overridden bean definitions.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>This version of {@code beanNamesForTypeIncludingAncestors} automatically
	 * includes prototypes and FactoryBeans.
	 * @param lbf the bean factory
	 * @param type the type that beans must match (as a {@code ResolvableType})
	 * @return the array of matching bean names, or an empty array if none
	 * @since 4.2
	 * @see ListableBeanFactory#getBeanNamesForType(ResolvableType)
	 */
	public static String[] beanNamesForTypeIncludingAncestors(ListableBeanFactory lbf, ResolvableType type) {
		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		String[] result = lbf.getBeanNamesForType(type);
		// 通过`HierarchicalBeanFactory`类型的工厂继承关系,
		// 从而达到bean名称统计的目的
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				String[] parentResult = beanNamesForTypeIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), type);
				result = mergeNamesWithParent(result, parentResult, hbf);
			}
		}
		return result;
	}

	/**
	 * 获取包含祖先在内的特定类型的bean名称数组,
	 * 同时指定是否包含单例,以及是否允许预初始化
	 * Get all bean names for the given type, including those defined in ancestor
	 * factories. Will return unique names in case of overridden bean definitions.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit"
	 * flag is set, which means that FactoryBeans will get initialized. If the
	 * object created by the FactoryBean doesn't match, the raw FactoryBean itself
	 * will be matched against the type. If "allowEagerInit" is not set,
	 * only raw FactoryBeans will be checked (which doesn't require initialization
	 * of each FactoryBean).
	 * @param lbf the bean factory
	 * @param type the type that beans must match (as a {@code ResolvableType})
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @return the array of matching bean names, or an empty array if none
	 * @since 5.2
	 * @see ListableBeanFactory#getBeanNamesForType(ResolvableType, boolean, boolean)
	 */
	public static String[] beanNamesForTypeIncludingAncestors(
			ListableBeanFactory lbf, ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {

		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		String[] result = lbf.getBeanNamesForType(type, includeNonSingletons, allowEagerInit);
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				String[] parentResult = beanNamesForTypeIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), type, includeNonSingletons, allowEagerInit);
				result = mergeNamesWithParent(result, parentResult, hbf);
			}
		}
		return result;
	}

	/**
	 * 获取包含祖先在内的特定类型的bean名称数组。
	 * 这儿的特定类型指的是Class这种类型
	 * Get all bean names for the given type, including those defined in ancestor
	 * factories. Will return unique names in case of overridden bean definitions.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>This version of {@code beanNamesForTypeIncludingAncestors} automatically
	 * includes prototypes and FactoryBeans.
	 * @param lbf the bean factory
	 * @param type the type that beans must match (as a {@code Class})
	 * @return the array of matching bean names, or an empty array if none
	 * @see ListableBeanFactory#getBeanNamesForType(Class)
	 */
	public static String[] beanNamesForTypeIncludingAncestors(ListableBeanFactory lbf, Class<?> type) {
		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		String[] result = lbf.getBeanNamesForType(type);
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				String[] parentResult = beanNamesForTypeIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), type);
				result = mergeNamesWithParent(result, parentResult, hbf);
			}
		}
		return result;
	}

	/**
	 * 获取包含祖先在内的特定类型的bean名称数组,
	 * 同时指定是否包含单例,以及是否允许预初始化,
	 * 这儿的特定类型指的是Class这种类型
	 * Get all bean names for the given type, including those defined in ancestor
	 * factories. Will return unique names in case of overridden bean definitions.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit"
	 * flag is set, which means that FactoryBeans will get initialized. If the
	 * object created by the FactoryBean doesn't match, the raw FactoryBean itself
	 * will be matched against the type. If "allowEagerInit" is not set,
	 * only raw FactoryBeans will be checked (which doesn't require initialization
	 * of each FactoryBean).
	 * @param lbf the bean factory
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @param type the type that beans must match
	 * @return the array of matching bean names, or an empty array if none
	 * @see ListableBeanFactory#getBeanNamesForType(Class, boolean, boolean)
	 */
	public static String[] beanNamesForTypeIncludingAncestors(
			ListableBeanFactory lbf, Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {

		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		String[] result = lbf.getBeanNamesForType(type, includeNonSingletons, allowEagerInit);
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				String[] parentResult = beanNamesForTypeIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), type, includeNonSingletons, allowEagerInit);
				result = mergeNamesWithParent(result, parentResult, hbf);
			}
		}
		return result;
	}

	/**
	 * 获取包含祖先在内的特定类型(且使用了特定注解)的bean名称数组
	 * Get all bean names whose {@code Class} has the supplied {@link Annotation}
	 * type, including those defined in ancestor factories, without creating any bean
	 * instances yet. Will return unique names in case of overridden bean definitions.
	 * @param lbf the bean factory
	 * @param annotationType the type of annotation to look for
	 * @return the array of matching bean names, or an empty array if none
	 * @since 5.0
	 * @see ListableBeanFactory#getBeanNamesForAnnotation(Class)
	 */
	public static String[] beanNamesForAnnotationIncludingAncestors(
			ListableBeanFactory lbf, Class<? extends Annotation> annotationType) {

		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		String[] result = lbf.getBeanNamesForAnnotation(annotationType);
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				String[] parentResult = beanNamesForAnnotationIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), annotationType);
				result = mergeNamesWithParent(result, parentResult, hbf);
			}
		}
		return result;
	}


	// Retrieval of bean instances

	/**
	 * 获取包含祖先在内的特定类型的bean实例map(key为bean名称,value为bean实例)
	 * Return all beans of the given type or subtypes, also picking up beans defined in
	 * ancestor bean factories if the current bean factory is a HierarchicalBeanFactory.
	 * The returned Map will only contain beans of this type.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p><b>Note: Beans of the same name will take precedence at the 'lowest' factory level,
	 * i.e. such beans will be returned from the lowest factory that they are being found in,
	 * hiding corresponding beans in ancestor factories.</b> This feature allows for
	 * 'replacing' beans by explicitly choosing the same bean name in a child factory;
	 * the bean in the ancestor factory won't be visible then, not even for by-type lookups.
	 * @param lbf the bean factory
	 * @param type type of bean to match
	 * @return the Map of matching bean instances, or an empty Map if none
	 * @throws BeansException if a bean could not be created
	 * @see ListableBeanFactory#getBeansOfType(Class)
	 */
	public static <T> Map<String, T> beansOfTypeIncludingAncestors(ListableBeanFactory lbf, Class<T> type)
			throws BeansException {

		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		Map<String, T> result = new LinkedHashMap<>(4);
		result.putAll(lbf.getBeansOfType(type));
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				Map<String, T> parentResult = beansOfTypeIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), type);
				parentResult.forEach((beanName, beanInstance) -> {
					if (!result.containsKey(beanName) && !hbf.containsLocalBean(beanName)) {
						result.put(beanName, beanInstance);
					}
				});
			}
		}
		return result;
	}

	/**
	 * 获取包含祖先在内的特定类型的bean实例map(key为bean名称,value为bean实例)
	 * 同时指定是否包含单例,以及是否允许预初始化,
	 * Return all beans of the given type or subtypes, also picking up beans defined in
	 * ancestor bean factories if the current bean factory is a HierarchicalBeanFactory.
	 * The returned Map will only contain beans of this type.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit" flag is set,
	 * which means that FactoryBeans will get initialized. If the object created by the
	 * FactoryBean doesn't match, the raw FactoryBean itself will be matched against the
	 * type. If "allowEagerInit" is not set, only raw FactoryBeans will be checked
	 * (which doesn't require initialization of each FactoryBean).
	 * <p><b>Note: Beans of the same name will take precedence at the 'lowest' factory level,
	 * i.e. such beans will be returned from the lowest factory that they are being found in,
	 * hiding corresponding beans in ancestor factories.</b> This feature allows for
	 * 'replacing' beans by explicitly choosing the same bean name in a child factory;
	 * the bean in the ancestor factory won't be visible then, not even for by-type lookups.
	 * @param lbf the bean factory
	 * @param type type of bean to match
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @return the Map of matching bean instances, or an empty Map if none
	 * @throws BeansException if a bean could not be created
	 * @see ListableBeanFactory#getBeansOfType(Class, boolean, boolean)
	 */
	public static <T> Map<String, T> beansOfTypeIncludingAncestors(
			ListableBeanFactory lbf, Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
			throws BeansException {

		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		Map<String, T> result = new LinkedHashMap<>(4);
		result.putAll(lbf.getBeansOfType(type, includeNonSingletons, allowEagerInit));
		if (lbf instanceof HierarchicalBeanFactory) {
			HierarchicalBeanFactory hbf = (HierarchicalBeanFactory) lbf;
			if (hbf.getParentBeanFactory() instanceof ListableBeanFactory) {
				Map<String, T> parentResult = beansOfTypeIncludingAncestors(
						(ListableBeanFactory) hbf.getParentBeanFactory(), type, includeNonSingletons, allowEagerInit);
				parentResult.forEach((beanName, beanInstance) -> {
					if (!result.containsKey(beanName) && !hbf.containsLocalBean(beanName)) {
						result.put(beanName, beanInstance);
					}
				});
			}
		}
		return result;
	}

	/**
	 * 获取包含祖先在内的特定类型的bean实例,这儿通过`uniqueBean`方法校验唯一性
	 * Return a single bean of the given type or subtypes, also picking up beans
	 * defined in ancestor bean factories if the current bean factory is a
	 * HierarchicalBeanFactory. Useful convenience method when we expect a
	 * single bean and don't care about the bean name.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>This version of {@code beanOfTypeIncludingAncestors} automatically includes
	 * prototypes and FactoryBeans.
	 * <p><b>Note: Beans of the same name will take precedence at the 'lowest' factory level,
	 * i.e. such beans will be returned from the lowest factory that they are being found in,
	 * hiding corresponding beans in ancestor factories.</b> This feature allows for
	 * 'replacing' beans by explicitly choosing the same bean name in a child factory;
	 * the bean in the ancestor factory won't be visible then, not even for by-type lookups.
	 * @param lbf the bean factory
	 * @param type type of bean to match
	 * @return the matching bean instance
	 * @throws NoSuchBeanDefinitionException if no bean of the given type was found
	 * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
	 * @throws BeansException if the bean could not be created
	 * @see #beansOfTypeIncludingAncestors(ListableBeanFactory, Class)
	 */
	public static <T> T beanOfTypeIncludingAncestors(ListableBeanFactory lbf, Class<T> type)
			throws BeansException {

		Map<String, T> beansOfType = beansOfTypeIncludingAncestors(lbf, type);
		return uniqueBean(type, beansOfType);
	}

	/**
	 * 获取包含祖先在内的特定类型的bean实例,这儿通过`uniqueBean`方法校验唯一性
	 * 同时指定是否包含单例,以及是否允许预初始化,
	 * Return a single bean of the given type or subtypes, also picking up beans
	 * defined in ancestor bean factories if the current bean factory is a
	 * HierarchicalBeanFactory. Useful convenience method when we expect a
	 * single bean and don't care about the bean name.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit" flag is set,
	 * which means that FactoryBeans will get initialized. If the object created by the
	 * FactoryBean doesn't match, the raw FactoryBean itself will be matched against the
	 * type. If "allowEagerInit" is not set, only raw FactoryBeans will be checked
	 * (which doesn't require initialization of each FactoryBean).
	 * <p><b>Note: Beans of the same name will take precedence at the 'lowest' factory level,
	 * i.e. such beans will be returned from the lowest factory that they are being found in,
	 * hiding corresponding beans in ancestor factories.</b> This feature allows for
	 * 'replacing' beans by explicitly choosing the same bean name in a child factory;
	 * the bean in the ancestor factory won't be visible then, not even for by-type lookups.
	 * @param lbf the bean factory
	 * @param type type of bean to match
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @return the matching bean instance
	 * @throws NoSuchBeanDefinitionException if no bean of the given type was found
	 * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
	 * @throws BeansException if the bean could not be created
	 * @see #beansOfTypeIncludingAncestors(ListableBeanFactory, Class, boolean, boolean)
	 */
	public static <T> T beanOfTypeIncludingAncestors(
			ListableBeanFactory lbf, Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
			throws BeansException {

		Map<String, T> beansOfType = beansOfTypeIncludingAncestors(lbf, type, includeNonSingletons, allowEagerInit);
		return uniqueBean(type, beansOfType);
	}

	/**
	 * 获取包含祖先在内的特定类型的bean实例,这儿通过`uniqueBean`方法校验唯一性
	 * Return a single bean of the given type or subtypes, not looking in ancestor
	 * factories. Useful convenience method when we expect a single bean and
	 * don't care about the bean name.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>This version of {@code beanOfType} automatically includes
	 * prototypes and FactoryBeans.
	 * @param lbf the bean factory
	 * @param type type of bean to match
	 * @return the matching bean instance
	 * @throws NoSuchBeanDefinitionException if no bean of the given type was found
	 * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
	 * @throws BeansException if the bean could not be created
	 * @see ListableBeanFactory#getBeansOfType(Class)
	 */
	public static <T> T beanOfType(ListableBeanFactory lbf, Class<T> type) throws BeansException {
		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		Map<String, T> beansOfType = lbf.getBeansOfType(type);
		return uniqueBean(type, beansOfType);
	}

	/**
	 * 获取特定类型的bean实例,这儿通过`uniqueBean`方法校验唯一性
	 * 同时指定是否包含单例,以及是否允许预初始化,
	 * Return a single bean of the given type or subtypes, not looking in ancestor
	 * factories. Useful convenience method when we expect a single bean and
	 * don't care about the bean name.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit"
	 * flag is set, which means that FactoryBeans will get initialized. If the
	 * object created by the FactoryBean doesn't match, the raw FactoryBean itself
	 * will be matched against the type. If "allowEagerInit" is not set,
	 * only raw FactoryBeans will be checked (which doesn't require initialization
	 * of each FactoryBean).
	 * @param lbf the bean factory
	 * @param type type of bean to match
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @return the matching bean instance
	 * @throws NoSuchBeanDefinitionException if no bean of the given type was found
	 * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
	 * @throws BeansException if the bean could not be created
	 * @see ListableBeanFactory#getBeansOfType(Class, boolean, boolean)
	 */
	public static <T> T beanOfType(
			ListableBeanFactory lbf, Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
			throws BeansException {

		Assert.notNull(lbf, "ListableBeanFactory must not be null");
		Map<String, T> beansOfType = lbf.getBeansOfType(type, includeNonSingletons, allowEagerInit);
		return uniqueBean(type, beansOfType);
	}


	/**
	 * 合并bean名称,内部通过List的addAll方法实现
	 * Merge the given bean names result with the given parent result.
	 * @param result the local bean name result
	 * @param parentResult the parent bean name result (possibly empty)
	 * @param hbf the local bean factory
	 * @return the merged result (possibly the local result as-is)
	 * @since 4.3.15
	 */
	private static String[] mergeNamesWithParent(String[] result, String[] parentResult, HierarchicalBeanFactory hbf) {
		if (parentResult.length == 0) {
			return result;
		}
		List<String> merged = new ArrayList<>(result.length + parentResult.length);
		merged.addAll(Arrays.asList(result));
		for (String beanName : parentResult) {
			if (!merged.contains(beanName) && !hbf.containsLocalBean(beanName)) {
				merged.add(beanName);
			}
		}
		return StringUtils.toStringArray(merged);
	}

	/**
	 * 校验map的唯一性
	 * Extract a unique bean for the given type from the given Map of matching beans.
	 * @param type type of bean to match
	 * @param matchingBeans all matching beans found
	 * @return the unique bean instance
	 * @throws NoSuchBeanDefinitionException if no bean of the given type was found
	 * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
	 */
	private static <T> T uniqueBean(Class<T> type, Map<String, T> matchingBeans) {
		int count = matchingBeans.size();
		if (count == 1) {
			return matchingBeans.values().iterator().next();
		}
		else if (count > 1) {
			throw new NoUniqueBeanDefinitionException(type, matchingBeans.keySet());
		}
		else {
			throw new NoSuchBeanDefinitionException(type);
		}
	}
}

总结

通过上面我们对源码的分析,我们大致看出此工具类包含以下几类方法:

  1. isFactoryDereference – 根据名称判断是否是一个工厂bean的名称
  2. transformedBeanName – 将带有&的所有前缀全部去掉
  3. isGeneratedBeanName – 判断是否内部生成的bean名称
  4. originalBeanName – 获取内部bean所在的外部bean
  5. countBeansIncludingAncestors – 获取包含祖先在内的所有bean的数量
  6. beanNamesForTypeIncludingAncestors – 获取包含祖先在内的bean名称数组,存在多个重载方法
  7. beansOfTypeIncludingAncestors – 获取包含祖先在内的bean实例map,存在多个重载方法
  8. beanOfTypeIncludingAncestors – 获取包含祖先在内的bean实例,存在多个重载方法
  9. beanOfType – 获取特定类型的bean实例(不包含祖先)

所有这些方法,基本都是对bean名称、bean实例、bean类型的判断和处理,是构成spring ioc的核心工具类方法。


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