spring的DefaultListableBeanFactory

DefaultListableBeanFactory

public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
		implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
	@Nullable
	private static Class<?> javaxInjectProviderClass;
	static {
		try {
			javaxInjectProviderClass =
					ClassUtils.forName("javax.inject.Provider", DefaultListableBeanFactory.class.getClassLoader());
		}
		catch (ClassNotFoundException ex) {
			// JSR-330 API not available - Provider interface simply not supported then.
			javaxInjectProviderClass = null;
		}
	}
	/** Map from serialized id to factory instance. */
	private static final Map<String, Reference<DefaultListableBeanFactory>> serializableFactories =
			new ConcurrentHashMap<>(8);
	/** Optional id for this factory, for serialization purposes. */
	@Nullable
	private String serializationId;
	/** Whether to allow re-registration of a different definition with the same name. */
	// 是否允許同名的不同BeanDefinition再次註冊  覆蓋
	private boolean allowBeanDefinitionOverriding = true;
	/** Whether to allow eager class loading even for lazy-init beans. */
	// 是否允許 eager 類(lazy init)的加載， 即使延遲初始化bean
	private boolean allowEagerClassLoading = true;
	/** Optional OrderComparator for dependency Lists and arrays. */
	@Nullable
	private Comparator<Object> dependencyComparator;
	/** Resolver to use for checking if a bean definition is an autowire candidate. */
	// 是一個策略接口，用來決定一個特定的bean Definition是否滿足特定依賴的自動綁定的候選項 
	private AutowireCandidateResolver autowireCandidateResolver = new SimpleAutowireCandidateResolver();
	/** Map from dependency type to corresponding autowired value. */
	// 定義依賴類型和其他對應的自動綁定值的鍵值對集合
	private final Map<Class<?>, Object> resolvableDependencies = new ConcurrentHashMap<>(16);
	/** Map of bean definition objects, keyed by bean name.  */
	// 存儲註冊信息的BeanDefinition
	private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);
	/** Map of singleton and non-singleton bean names, keyed by dependency type. */
	private final Map<Class<?>, String[]> allBeanNamesByType = new ConcurrentHashMap<>(64);
	/** Map of singleton-only bean names, keyed by dependency type. */
	private final Map<Class<?>, String[]> singletonBeanNamesByType = new ConcurrentHashMap<>(64);
	/** List of bean definition names, in registration order. */
	// beanDefinition 所有的名稱
	private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
	/** List of names of manually registered singletons, in registration order. */
	// 手動註冊bean的單例，不是通過 beanDefinition 生成的單例 
	private volatile Set<String> manualSingletonNames = new LinkedHashSet<>(16);
	/** Cached array of bean definition names in case of frozen configuration. */
	@Nullable
	private volatile String[] frozenBeanDefinitionNames;
	/** Whether bean definition metadata may be cached for all beans. */
	private volatile boolean configurationFrozen = false;
	public DefaultListableBeanFactory() {
		super();
	}
	public DefaultListableBeanFactory(@Nullable BeanFactory parentBeanFactory) {
		super(parentBeanFactory);
	}
	// 用戶beanFactory序列化
	public void setSerializationId(@Nullable String serializationId) {
		if (serializationId != null) {
			serializableFactories.put(serializationId, new WeakReference<>(this));
		}
		else if (this.serializationId != null) {
			serializableFactories.remove(this.serializationId);
		}
		this.serializationId = serializationId;
	}

	@Nullable
	public String getSerializationId() {
		return this.serializationId;
	}
	public void setAllowBeanDefinitionOverriding(boolean allowBeanDefinitionOverriding) {
		this.allowBeanDefinitionOverriding = allowBeanDefinitionOverriding;
	}
	public boolean isAllowBeanDefinitionOverriding() {
		return this.allowBeanDefinitionOverriding;
	}
	public void setAllowEagerClassLoading(boolean allowEagerClassLoading) {
		this.allowEagerClassLoading = allowEagerClassLoading;
	}
	public boolean isAllowEagerClassLoading() {
		return this.allowEagerClassLoading;
	}
	public void setDependencyComparator(@Nullable Comparator<Object> dependencyComparator) {
		this.dependencyComparator = dependencyComparator;
	}
	@Nullable
	public Comparator<Object> getDependencyComparator() {
		return this.dependencyComparator;
	}
	public void setAutowireCandidateResolver(final AutowireCandidateResolver autowireCandidateResolver) {
		Assert.notNull(autowireCandidateResolver, "AutowireCandidateResolver must not be null");
		if (autowireCandidateResolver instanceof BeanFactoryAware) {
			if (System.getSecurityManager() != null) {
				AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
					((BeanFactoryAware) autowireCandidateResolver).setBeanFactory(DefaultListableBeanFactory.this);
					return null;
				}, getAccessControlContext());
			}
			else {
				((BeanFactoryAware) autowireCandidateResolver).setBeanFactory(this);
			}
		}
		this.autowireCandidateResolver = autowireCandidateResolver;
	}
	public AutowireCandidateResolver getAutowireCandidateResolver() {
		return this.autowireCandidateResolver;
	}
	@Override
	public void copyConfigurationFrom(ConfigurableBeanFactory otherFactory) {
		super.copyConfigurationFrom(otherFactory);
		if (otherFactory instanceof DefaultListableBeanFactory) {
			DefaultListableBeanFactory otherListableFactory = (DefaultListableBeanFactory) otherFactory;
			this.allowBeanDefinitionOverriding = otherListableFactory.allowBeanDefinitionOverriding;
			this.allowEagerClassLoading = otherListableFactory.allowEagerClassLoading;
			this.dependencyComparator = otherListableFactory.dependencyComparator;
			// A clone of the AutowireCandidateResolver since it is potentially BeanFactoryAware...
			setAutowireCandidateResolver(
				BeanUtils.instantiateClass(otherListableFactory.getAutowireCandidateResolver().getClass()));
			// Make resolvable dependencies (e.g. ResourceLoader) available here as well...
			this.resolvableDependencies.putAll(otherListableFactory.resolvableDependencies);
		}
	}

	//---------------------------------------------------------------------
	// Implementation of remaining BeanFactory methods
	//---------------------------------------------------------------------
	@Override
	public <T> T getBean(Class<T> requiredType) throws BeansException {
		return getBean(requiredType, (Object[]) null);
	}
	@SuppressWarnings("unchecked")
	@Override
	public <T> T getBean(Class<T> requiredType, @Nullable Object... args) throws BeansException {
		Assert.notNull(requiredType, "Required type must not be null");
		Object resolved = resolveBean(ResolvableType.forRawClass(requiredType), args, false);
		if (resolved == null) {
			throw new NoSuchBeanDefinitionException(requiredType);
		}
		return (T) resolved;
	}
	@Override
	public <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType) throws BeansException {
		Assert.notNull(requiredType, "Required type must not be null");
		return getBeanProvider(ResolvableType.forRawClass(requiredType));
	}
	@SuppressWarnings("unchecked")
	@Override
	public <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType) {
		return new BeanObjectProvider<T>() {
			@Override
			public T getObject() throws BeansException {
				T resolved = resolveBean(requiredType, null, false);
				if (resolved == null) {
					throw new NoSuchBeanDefinitionException(requiredType);
				}
				return resolved;
			}
			@Override
			public T getObject(Object... args) throws BeansException {
				T resolved = resolveBean(requiredType, args, false);
				if (resolved == null) {
					throw new NoSuchBeanDefinitionException(requiredType);
				}
				return resolved;
			}
			@Override
			@Nullable
			public T getIfAvailable() throws BeansException {
				return resolveBean(requiredType, null, false);
			}
			@Override
			@Nullable
			public T getIfUnique() throws BeansException {
				return resolveBean(requiredType, null, true);
			}
			@Override
			public Stream<T> stream() {
				return Arrays.stream(getBeanNamesForTypedStream(requiredType))
						.map(name -> (T) getBean(name))
						.filter(bean -> !(bean instanceof NullBean));
			}
			@Override
			public Stream<T> orderedStream() {
				String[] beanNames = getBeanNamesForTypedStream(requiredType);
				Map<String, T> matchingBeans = new LinkedHashMap<>(beanNames.length);
				for (String beanName : beanNames) {
					Object beanInstance = getBean(beanName);
					if (!(beanInstance instanceof NullBean)) {
						matchingBeans.put(beanName, (T) beanInstance);
					}
				}
				Stream<T> stream = matchingBeans.values().stream();
				return stream.sorted(adaptOrderComparator(matchingBeans));
			}
		};
	}

	@Nullable
	private <T> T resolveBean(ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) {
		// 獲取beanHolder 
		NamedBeanHolder<T> namedBean = resolveNamedBean(requiredType, args, nonUniqueAsNull);
		if (namedBean != null) {
			return namedBean.getBeanInstance();
		}
		// 從父容器中獲取 
		BeanFactory parent = getParentBeanFactory();
		if (parent instanceof DefaultListableBeanFactory) {
			return ((DefaultListableBeanFactory) parent).resolveBean(requiredType, args, nonUniqueAsNull);
		}
		else if (parent != null) {
			ObjectProvider<T> parentProvider = parent.getBeanProvider(requiredType);
			if (args != null) {
				return parentProvider.getObject(args);
			}
			else {
				return (nonUniqueAsNull ? parentProvider.getIfUnique() : parentProvider.getIfAvailable());
			}
		}
		return null;
	}

	private String[] getBeanNamesForTypedStream(ResolvableType requiredType) {
		return BeanFactoryUtils.beanNamesForTypeIncludingAncestors(this, requiredType);
	}


	//---------------------------------------------------------------------
	// Implementation of ListableBeanFactory interface
	//---------------------------------------------------------------------

	@Override
	public boolean containsBeanDefinition(String beanName) {
		Assert.notNull(beanName, "Bean name must not be null");
		return this.beanDefinitionMap.containsKey(beanName);
	}

	@Override
	public int getBeanDefinitionCount() {
		return this.beanDefinitionMap.size();
	}

	@Override
	public String[] getBeanDefinitionNames() {
		String[] frozenNames = this.frozenBeanDefinitionNames;
		if (frozenNames != null) {
			return frozenNames.clone();
		}
		else {
			return StringUtils.toStringArray(this.beanDefinitionNames);
		}
	}

	@Override
	public String[] getBeanNamesForType(ResolvableType type) {
		return getBeanNamesForType(type, true, true);
	}

	@Override
	public String[] getBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
		Class<?> resolved = type.resolve();
		if (resolved != null && !type.hasGenerics()) {
			return getBeanNamesForType(resolved, includeNonSingletons, allowEagerInit);
		}
		else {
			return doGetBeanNamesForType(type, includeNonSingletons, allowEagerInit);
		}
	}

	@Override
	public String[] getBeanNamesForType(@Nullable Class<?> type) {
		return getBeanNamesForType(type, true, true);
	}

	@Override
	public String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit) {
		if (!isConfigurationFrozen() || type == null || !allowEagerInit) {
			return doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, allowEagerInit);
		}
		Map<Class<?>, String[]> cache =
				(includeNonSingletons ? this.allBeanNamesByType : this.singletonBeanNamesByType);
		String[] resolvedBeanNames = cache.get(type);
		if (resolvedBeanNames != null) {
			return resolvedBeanNames;
		}
		resolvedBeanNames = doGetBeanNamesForType(ResolvableType.forRawClass(type), includeNonSingletons, true);
		if (ClassUtils.isCacheSafe(type, getBeanClassLoader())) {
			cache.put(type, resolvedBeanNames);
		}
		return resolvedBeanNames;
	}
	//  獲取 ResolvableType 對應的所有bean名稱
	private String[] doGetBeanNamesForType(ResolvableType type, boolean includeNonSingletons, boolean allowEagerInit) {
		List<String> result = new ArrayList<>();
		// Check all bean definitions. 遍歷所有的bean定義 
		for (String beanName : this.beanDefinitionNames) {
			// Only consider bean as eligible if the bean name
			// is not defined as alias for some other bean.
			if (!isAlias(beanName)) { // 非別名
				try {
					RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
					// Only check bean definition if it is complete.
					// 非抽象,允許預實例化 等判斷條件
					if (!mbd.isAbstract() && (allowEagerInit ||
							(mbd.hasBeanClass() || !mbd.isLazyInit() || isAllowEagerClassLoading()) &&
									!requiresEagerInitForType(mbd.getFactoryBeanName()))) {
						boolean isFactoryBean = isFactoryBean(beanName, mbd);
						BeanDefinitionHolder dbd = mbd.getDecoratedDefinition();
						boolean matchFound = false;
						boolean allowFactoryBeanInit = allowEagerInit || containsSingleton(beanName);
						boolean isNonLazyDecorated = dbd != null && !mbd.isLazyInit();
						if (!isFactoryBean) {
							if (includeNonSingletons || isSingleton(beanName, mbd, dbd)) {
								matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
							}
						}
						else  {
							if (includeNonSingletons || isNonLazyDecorated ||
									(allowFactoryBeanInit && isSingleton(beanName, mbd, dbd))) {
								matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
							}
							if (!matchFound) {
								// In case of FactoryBean, try to match FactoryBean instance itself next.
								beanName = FACTORY_BEAN_PREFIX + beanName;
								matchFound = isTypeMatch(beanName, type, allowFactoryBeanInit);
							}
						}
						if (matchFound) {
							result.add(beanName);
						}
					}
				}
				catch (CannotLoadBeanClassException | BeanDefinitionStoreException ex) {
					if (allowEagerInit) {
						throw ex;
					}
					// Probably a placeholder: let's ignore it for type matching purposes.
					LogMessage message = (ex instanceof CannotLoadBeanClassException) ?
							LogMessage.format("Ignoring bean class loading failure for bean '%s'", beanName) :
							LogMessage.format("Ignoring unresolvable metadata in bean definition '%s'", beanName);
					logger.trace(message, ex);
					onSuppressedException(ex);
				}
			}
		}
		// Check manually registered singletons too. 手動註冊的單例 
		for (String beanName : this.manualSingletonNames) {
			try {
				// In case of FactoryBean, match object created by FactoryBean.
				if (isFactoryBean(beanName)) {
					if ((includeNonSingletons || isSingleton(beanName)) && isTypeMatch(beanName, type)) {
						result.add(beanName);
						// Match found for this bean: do not match FactoryBean itself anymore.
						continue;
					}
					// In case of FactoryBean, try to match FactoryBean itself next.
					beanName = FACTORY_BEAN_PREFIX + beanName;
				}
				// Match raw bean instance (might be raw FactoryBean).
				if (isTypeMatch(beanName, type)) {
					result.add(beanName);
				}
			}
			catch (NoSuchBeanDefinitionException ex) {
				// Shouldn't happen - probably a result of circular reference resolution...
				logger.trace(LogMessage.format("Failed to check manually registered singleton with name '%s'", beanName), ex);
			}
		}

		return StringUtils.toStringArray(result);
	}

	private boolean isSingleton(String beanName, RootBeanDefinition mbd, @Nullable BeanDefinitionHolder dbd) {
		return (dbd != null ? mbd.isSingleton() : isSingleton(beanName));
	}

	/**
	 * Check whether the specified bean would need to be eagerly initialized
	 * in order to determine its type.
	 * @param factoryBeanName a factory-bean reference that the bean definition
	 * defines a factory method for
	 * @return whether eager initialization is necessary
	 */
	private boolean requiresEagerInitForType(@Nullable String factoryBeanName) {
		return (factoryBeanName != null && isFactoryBean(factoryBeanName) && !containsSingleton(factoryBeanName));
	}

	@Override
	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException {
		return getBeansOfType(type, true, true);
	}

	@Override
	@SuppressWarnings("unchecked")
	public <T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
			throws BeansException {

		String[] beanNames = getBeanNamesForType(type, includeNonSingletons, allowEagerInit);
		Map<String, T> result = new LinkedHashMap<>(beanNames.length);
		for (String beanName : beanNames) {
			try {
				Object beanInstance = getBean(beanName);
				if (!(beanInstance instanceof NullBean)) {
					result.put(beanName, (T) beanInstance);
				}
			}
			catch (BeanCreationException ex) {
				Throwable rootCause = ex.getMostSpecificCause();
				if (rootCause instanceof BeanCurrentlyInCreationException) {
					BeanCreationException bce = (BeanCreationException) rootCause;
					String exBeanName = bce.getBeanName();
					if (exBeanName != null && isCurrentlyInCreation(exBeanName)) {
						if (logger.isTraceEnabled()) {
							logger.trace("Ignoring match to currently created bean '" + exBeanName + "': " +
									ex.getMessage());
						}
						onSuppressedException(ex);
						// Ignore: indicates a circular reference when autowiring constructors.
						// We want to find matches other than the currently created bean itself.
						continue;
					}
				}
				throw ex;
			}
		}
		return result;
	}
	// 獲取註釋annotationType所有的bean的名稱 r
	@Override
	public String[] getBeanNamesForAnnotation(Class<? extends Annotation> annotationType) {
		List<String> result = new ArrayList<>();
		for (String beanName : this.beanDefinitionNames) {
			BeanDefinition beanDefinition = getBeanDefinition(beanName);
			if (!beanDefinition.isAbstract() && findAnnotationOnBean(beanName, annotationType) != null) {
				result.add(beanName);
			}
		}
		for (String beanName : this.manualSingletonNames) {
			if (!result.contains(beanName) && findAnnotationOnBean(beanName, annotationType) != null) {
				result.add(beanName);
			}
		}
		return StringUtils.toStringArray(result);
	}

	@Override
	public Map<String, Object> getBeansWithAnnotation(Class<? extends Annotation> annotationType) {
		String[] beanNames = getBeanNamesForAnnotation(annotationType);
		Map<String, Object> result = new LinkedHashMap<>(beanNames.length);
		for (String beanName : beanNames) {
			Object beanInstance = getBean(beanName);
			if (!(beanInstance instanceof NullBean)) {
				result.put(beanName, beanInstance);
			}
		}
		return result;
	}

	@Override
	@Nullable
	public <A extends Annotation> A findAnnotationOnBean(String beanName, Class<A> annotationType)
			throws NoSuchBeanDefinitionException {

		return findMergedAnnotationOnBean(beanName, annotationType)
				.synthesize(MergedAnnotation::isPresent).orElse(null);
	}

	private <A extends Annotation> MergedAnnotation<A> findMergedAnnotationOnBean(
			String beanName, Class<A> annotationType) {

		Class<?> beanType = getType(beanName);
		if (beanType != null) {
			MergedAnnotation<A> annotation =
					MergedAnnotations.from(beanType, SearchStrategy.TYPE_HIERARCHY).get(annotationType);
			if (annotation.isPresent()) {
				return annotation;
			}
		}
		if (containsBeanDefinition(beanName)) {
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
			// Check raw bean class, e.g. in case of a proxy.
			if (bd.hasBeanClass()) {
				Class<?> beanClass = bd.getBeanClass();
				if (beanClass != beanType) {
					MergedAnnotation<A> annotation =
							MergedAnnotations.from(beanClass, SearchStrategy.TYPE_HIERARCHY).get(annotationType);
					if (annotation.isPresent()) {
						return annotation;
					}
				}
			}
			// Check annotations declared on factory method, if any.
			Method factoryMethod = bd.getResolvedFactoryMethod();
			if (factoryMethod != null) {
				MergedAnnotation<A> annotation =
						MergedAnnotations.from(factoryMethod, SearchStrategy.TYPE_HIERARCHY).get(annotationType);
				if (annotation.isPresent()) {
					return annotation;
				}
			}
		}
		return MergedAnnotation.missing();
	}


	//---------------------------------------------------------------------
	// Implementation of ConfigurableListableBeanFactory interface
	//---------------------------------------------------------------------

	@Override
	public void registerResolvableDependency(Class<?> dependencyType, @Nullable Object autowiredValue) {
		Assert.notNull(dependencyType, "Dependency type must not be null");
		if (autowiredValue != null) {
			if (!(autowiredValue instanceof ObjectFactory || dependencyType.isInstance(autowiredValue))) {
				throw new IllegalArgumentException("Value [" + autowiredValue +
						"] does not implement specified dependency type [" + dependencyType.getName() + "]");
			}
			this.resolvableDependencies.put(dependencyType, autowiredValue);
		}
	}

	@Override
	public boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor)
			throws NoSuchBeanDefinitionException {

		return isAutowireCandidate(beanName, descriptor, getAutowireCandidateResolver());
	}

	/**
	 * Determine whether the specified bean definition qualifies as an autowire candidate,
	 * to be injected into other beans which declare a dependency of matching type.
	 * @param beanName the name of the bean definition to check
	 * @param descriptor the descriptor of the dependency to resolve
	 * @param resolver the AutowireCandidateResolver to use for the actual resolution algorithm
	 * @return whether the bean should be considered as autowire candidate
	 */
	protected boolean isAutowireCandidate(String beanName, DependencyDescriptor descriptor, AutowireCandidateResolver resolver)
			throws NoSuchBeanDefinitionException {

		String beanDefinitionName = BeanFactoryUtils.transformedBeanName(beanName);
		if (containsBeanDefinition(beanDefinitionName)) {
			return isAutowireCandidate(beanName, getMergedLocalBeanDefinition(beanDefinitionName), descriptor, resolver);
		}
		else if (containsSingleton(beanName)) {
			return isAutowireCandidate(beanName, new RootBeanDefinition(getType(beanName)), descriptor, resolver);
		}

		BeanFactory parent = getParentBeanFactory();
		if (parent instanceof DefaultListableBeanFactory) {
			// No bean definition found in this factory -> delegate to parent.
			return ((DefaultListableBeanFactory) parent).isAutowireCandidate(beanName, descriptor, resolver);
		}
		else if (parent instanceof ConfigurableListableBeanFactory) {
			// If no DefaultListableBeanFactory, can't pass the resolver along.
			return ((ConfigurableListableBeanFactory) parent).isAutowireCandidate(beanName, descriptor);
		}
		else {
			return true;
		}
	}

	protected boolean isAutowireCandidate(String beanName, RootBeanDefinition mbd,
			DependencyDescriptor descriptor, AutowireCandidateResolver resolver) {

		String beanDefinitionName = BeanFactoryUtils.transformedBeanName(beanName);
		resolveBeanClass(mbd, beanDefinitionName);
		if (mbd.isFactoryMethodUnique && mbd.factoryMethodToIntrospect == null) {
			new ConstructorResolver(this).resolveFactoryMethodIfPossible(mbd);
		}
		return resolver.isAutowireCandidate(
				new BeanDefinitionHolder(mbd, beanName, getAliases(beanDefinitionName)), descriptor);
	}

	@Override
	public BeanDefinition getBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
		BeanDefinition bd = this.beanDefinitionMap.get(beanName);
		if (bd == null) {
			if (logger.isTraceEnabled()) {
				logger.trace("No bean named '" + beanName + "' found in " + this);
			}
			throw new NoSuchBeanDefinitionException(beanName);
		}
		return bd;
	}

	@Override
	public Iterator<String> getBeanNamesIterator() {
		CompositeIterator<String> iterator = new CompositeIterator<>();
		iterator.add(this.beanDefinitionNames.iterator());
		iterator.add(this.manualSingletonNames.iterator());
		return iterator;
	}

	@Override
	public void clearMetadataCache() {
		super.clearMetadataCache();
		clearByTypeCache();
	}

	@Override
	public void freezeConfiguration() {
		this.configurationFrozen = true;
		this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
	}

	@Override
	public boolean isConfigurationFrozen() {
		return this.configurationFrozen;
	}
	@Override
	protected boolean isBeanEligibleForMetadataCaching(String beanName) {
		return (this.configurationFrozen || super.isBeanEligibleForMetadataCaching(beanName));
	}
	@Override 
	//  對配置Lazy-init屬性單例bean的進行預實例化
	public void preInstantiateSingletons() throws BeansException {
		if (logger.isTraceEnabled()) {
			logger.trace("Pre-instantiating singletons in " + this);
		}
		// Iterate over a copy to allow for init methods which in turn register new bean definitions.
		// While this may not be part of the regular factory bootstrap, it does otherwise work fine.
		// 獲取所有註冊到beandefinition容器的名稱，進行迭代
		List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);
		// Trigger initialization of all non-lazy singleton beans...
		// 觸發所有非lazy-init的單例bean實例化
		for (String beanName : beanNames) {
			// 獲取知道指定名稱beanName的bean定義
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
			// Bean 不是抽象的，是單例模式的，且lazy-init屬性爲false
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
				// 如果指定名稱bean是工廠bean(FactoryBean)
				if (isFactoryBean(beanName)) {
					//FACTORY_BEAN_PREFIX=”&”，當Bean名稱前面加”&”符號
					//時，獲取的是產生容器對象本身，而不是容器產生的Bean.
					//調用getBean方法，觸發容器對Bean實例化和依賴注入過程
					Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
					// 再次進行類型判斷
					if (bean instanceof FactoryBean) {
						final FactoryBean<?> factory = (FactoryBean<?>) bean;
						// 標識是否需要預實例化，SmartFactoryBean 有isEagerInit屬性  EagerInitFactory
						boolean isEagerInit;
						if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
							isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
											((SmartFactoryBean<?>) factory)::isEagerInit,
									getAccessControlContext());
						}
						else {
							isEagerInit = (factory instanceof SmartFactoryBean &&
									((SmartFactoryBean<?>) factory).isEagerInit());
						}
						if (isEagerInit) {
						 	// 調用getBean方法，觸發容器對Bean實例化和依賴注入過程
							getBean(beanName);
						}
					}
				}
				else {
					getBean(beanName);
				}
			}
		}

		// Trigger post-initialization callback for all applicable beans...
		// 觸發 post-initialization 實例化後的回調 回調bean實現SmartInitializingSingleton的接口
		for (String beanName : beanNames) {
			Object singletonInstance = getSingleton(beanName);
			if (singletonInstance instanceof SmartInitializingSingleton) {
				final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
				if (System.getSecurityManager() != null) {
					AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
						smartSingleton.afterSingletonsInstantiated();
						return null;
					}, getAccessControlContext());
				}
				else {
					smartSingleton.afterSingletonsInstantiated();
				}
			}
		}
	}


	//---------------------------------------------------------------------
	// Implementation of BeanDefinitionRegistry interface
	//---------------------------------------------------------------------
	@Override
	// 向IOC容器解析的BeanDefinition
	public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
			throws BeanDefinitionStoreException {
		Assert.hasText(beanName, "Bean name must not be empty");
		Assert.notNull(beanDefinition, "BeanDefinition must not be null");
		// 校驗解析的BeanDefinition
		if (beanDefinition instanceof AbstractBeanDefinition) {
			try {
				((AbstractBeanDefinition) beanDefinition).validate();
			}
			catch (BeanDefinitionValidationException ex) {
				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
						"Validation of bean definition failed", ex);
			}
		}
		// 從BeanDefinition緩存中獲取已有的bean定義
		BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
		if (existingDefinition != null) { 
			// 校驗 判斷bean定義是否可以覆蓋
			if (!isAllowBeanDefinitionOverriding()) {
				throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
			}
			// 日誌
			else if (existingDefinition.getRole() < beanDefinition.getRole()) {
				// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
				if (logger.isInfoEnabled()) {
					logger.info("Overriding user-defined bean definition for bean '" + beanName +
							"' with a framework-generated bean definition: replacing [" +
							existingDefinition + "] with [" + beanDefinition + "]");
				}
			}
			else if (!beanDefinition.equals(existingDefinition)) {
				if (logger.isDebugEnabled()) {
					logger.debug("Overriding bean definition for bean '" + beanName +
							"' with a different definition: replacing [" + existingDefinition +
							"] with [" + beanDefinition + "]");
				}
			}
			else {
				if (logger.isTraceEnabled()) {
					logger.trace("Overriding bean definition for bean '" + beanName +
							"' with an equivalent definition: replacing [" + existingDefinition +
							"] with [" + beanDefinition + "]");
				}
			}
			//覆蓋原有的bean定義
			this.beanDefinitionMap.put(beanName, beanDefinition);
		}
		else {
			if (hasBeanCreationStarted()) {
				// Cannot modify startup-time collection elements anymore (for stable iteration)
				// 數據一致性
				synchronized (this.beanDefinitionMap) { 
					// 註冊bean定義
					this.beanDefinitionMap.put(beanName, beanDefinition);
					// 更新bean的名稱 map
					List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
					updatedDefinitions.addAll(this.beanDefinitionNames);
					updatedDefinitions.add(beanName);
					this.beanDefinitionNames = updatedDefinitions;
					//上面是自動註冊的bean，刪除手動註冊bean單例
					removeManualSingletonName(beanName);
				}
			}
			else { 
				// 在容器啓動階段時註冊
				// Still in startup registration phase
				this.beanDefinitionMap.put(beanName, beanDefinition);
				this.beanDefinitionNames.add(beanName);
				removeManualSingletonName(beanName);
			}
			this.frozenBeanDefinitionNames = null;
		}
		// 檢查是否有同名的BeanDefinition已經在IOC容器中註冊
		if (existingDefinition != null || containsSingleton(beanName)) {
			 // 重置所有已經註冊過的BeanDefinition的緩存
			resetBeanDefinition(beanName);
		}
	}

	@Override
	public void removeBeanDefinition(String beanName) throws NoSuchBeanDefinitionException {
		Assert.hasText(beanName, "'beanName' must not be empty");

		BeanDefinition bd = this.beanDefinitionMap.remove(beanName);
		if (bd == null) {
			if (logger.isTraceEnabled()) {
				logger.trace("No bean named '" + beanName + "' found in " + this);
			}
			throw new NoSuchBeanDefinitionException(beanName);
		}

		if (hasBeanCreationStarted()) {
			// Cannot modify startup-time collection elements anymore (for stable iteration)
			synchronized (this.beanDefinitionMap) {
				List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames);
				updatedDefinitions.remove(beanName);
				this.beanDefinitionNames = updatedDefinitions;
			}
		}
		else {
			// Still in startup registration phase
			this.beanDefinitionNames.remove(beanName);
		}
		this.frozenBeanDefinitionNames = null;

		resetBeanDefinition(beanName);
	}

	protected void resetBeanDefinition(String beanName) {
		// Remove the merged bean definition for the given bean, if already created.
		clearMergedBeanDefinition(beanName);

		// Remove corresponding bean from singleton cache, if any. Shouldn't usually
		// be necessary, rather just meant for overriding a context's default beans
		// (e.g. the default StaticMessageSource in a StaticApplicationContext).
		destroySingleton(beanName);

		// Notify all post-processors that the specified bean definition has been reset.
		for (BeanPostProcessor processor : getBeanPostProcessors()) {
			if (processor instanceof MergedBeanDefinitionPostProcessor) {
				((MergedBeanDefinitionPostProcessor) processor).resetBeanDefinition(beanName);
			}
		}

		// Reset all bean definitions that have the given bean as parent (recursively).
		for (String bdName : this.beanDefinitionNames) {
			if (!beanName.equals(bdName)) {
				BeanDefinition bd = this.beanDefinitionMap.get(bdName);
				// Ensure bd is non-null due to potential concurrent modification
				// of the beanDefinitionMap.
				if (bd != null && beanName.equals(bd.getParentName())) {
					resetBeanDefinition(bdName);
				}
			}
		}
	}

	/**
	 * Only allows alias overriding if bean definition overriding is allowed.
	 */
	@Override
	protected boolean allowAliasOverriding() {
		return isAllowBeanDefinitionOverriding();
	}

	@Override
	public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
		super.registerSingleton(beanName, singletonObject);
		updateManualSingletonNames(set -> set.add(beanName), set -> !this.beanDefinitionMap.containsKey(beanName));
		clearByTypeCache();
	}

	@Override
	public void destroySingletons() {
		super.destroySingletons();
		updateManualSingletonNames(Set::clear, set -> !set.isEmpty());
		clearByTypeCache();
	}

	@Override
	public void destroySingleton(String beanName) {
		super.destroySingleton(beanName);
		removeManualSingletonName(beanName);
		clearByTypeCache();
	}

	private void removeManualSingletonName(String beanName) {
		updateManualSingletonNames(set -> set.remove(beanName), set -> set.contains(beanName));
	}

	private void updateManualSingletonNames(Consumer<Set<String>> action, Predicate<Set<String>> condition) {
		if (hasBeanCreationStarted()) {
			// Cannot modify startup-time collection elements anymore (for stable iteration)
			synchronized (this.beanDefinitionMap) {
				if (condition.test(this.manualSingletonNames)) {
					Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
					action.accept(updatedSingletons);
					this.manualSingletonNames = updatedSingletons;
				}
			}
		}
		else {
			// Still in startup registration phase
			if (condition.test(this.manualSingletonNames)) {
				action.accept(this.manualSingletonNames);
			}
		}
	}

	/**
	 * Remove any assumptions about by-type mappings.
	 */
	private void clearByTypeCache() {
		this.allBeanNamesByType.clear();
		this.singletonBeanNamesByType.clear();
	}


	//---------------------------------------------------------------------
	// Dependency resolution functionality
	//---------------------------------------------------------------------

	@Override
	public <T> NamedBeanHolder<T> resolveNamedBean(Class<T> requiredType) throws BeansException {
		Assert.notNull(requiredType, "Required type must not be null");
		NamedBeanHolder<T> namedBean = resolveNamedBean(ResolvableType.forRawClass(requiredType), null, false);
		if (namedBean != null) {
			return namedBean;
		}
		BeanFactory parent = getParentBeanFactory();
		if (parent instanceof AutowireCapableBeanFactory) {
			return ((AutowireCapableBeanFactory) parent).resolveNamedBean(requiredType);
		}
		throw new NoSuchBeanDefinitionException(requiredType);
	}

	@SuppressWarnings("unchecked")
	@Nullable
	private <T> NamedBeanHolder<T> resolveNamedBean(
			ResolvableType requiredType, @Nullable Object[] args, boolean nonUniqueAsNull) throws BeansException {

		Assert.notNull(requiredType, "Required type must not be null");
		String[] candidateNames = getBeanNamesForType(requiredType);

		if (candidateNames.length > 1) {
			List<String> autowireCandidates = new ArrayList<>(candidateNames.length);
			for (String beanName : candidateNames) {
				if (!containsBeanDefinition(beanName) || getBeanDefinition(beanName).isAutowireCandidate()) {
					autowireCandidates.add(beanName);
				}
			}
			if (!autowireCandidates.isEmpty()) {
				candidateNames = StringUtils.toStringArray(autowireCandidates);
			}
		}

		if (candidateNames.length == 1) {
			String beanName = candidateNames[0];
			return new NamedBeanHolder<>(beanName, (T) getBean(beanName, requiredType.toClass(), args));
		}
		else if (candidateNames.length > 1) {
			Map<String, Object> candidates = new LinkedHashMap<>(candidateNames.length);
			for (String beanName : candidateNames) {
				if (containsSingleton(beanName) && args == null) {
					Object beanInstance = getBean(beanName);
					candidates.put(beanName, (beanInstance instanceof NullBean ? null : beanInstance));
				}
				else {
					candidates.put(beanName, getType(beanName));
				}
			}
			// 選出 @Primary 的候選者
			String candidateName = determinePrimaryCandidate(candidates, requiredType.toClass());
			if (candidateName == null) { // 選出 高優先級的候選者 @Priority
				candidateName = determineHighestPriorityCandidate(candidates, requiredType.toClass());
			}
			if (candidateName != null) {
				Object beanInstance = candidates.get(candidateName);
				if (beanInstance == null || beanInstance instanceof Class) { 
					// 重新 實例化 獲取 候選者bean實例
					beanInstance = getBean(candidateName, requiredType.toClass(), args);
				}
				return new NamedBeanHolder<>(candidateName, (T) beanInstance);
			}
			if (!nonUniqueAsNull) {
				throw new NoUniqueBeanDefinitionException(requiredType, candidates.keySet());
			}
		}

		return null;
	}
	@Override
	@Nullable  // 尋找類型匹配的邏輯實現封裝在resolveDependency中 
	public Object resolveDependency(DependencyDescriptor descriptor, @Nullable String requestingBeanName,
			@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {
		descriptor.initParameterNameDiscovery(getParameterNameDiscoverer());
		if (Optional.class == descriptor.getDependencyType()) {
			return createOptionalDependency(descriptor, requestingBeanName);
		}
		else if (ObjectFactory.class == descriptor.getDependencyType() ||
				ObjectProvider.class == descriptor.getDependencyType()) {
			// ObjectFactory類注入特殊處理
			return new DependencyObjectProvider(descriptor, requestingBeanName);
		}
		else if (javaxInjectProviderClass == descriptor.getDependencyType()) {
			// javaxInjectProviderClass 類注入的特殊處理
			return new Jsr330Factory().createDependencyProvider(descriptor, requestingBeanName);
		}
		else {
		    // 通用處理邏輯
			Object result = getAutowireCandidateResolver().getLazyResolutionProxyIfNecessary(
					descriptor, requestingBeanName);
			if (result == null) {
				result = doResolveDependency(descriptor, requestingBeanName, autowiredBeanNames, typeConverter);
			}
			return result;
		}
	}

	@Nullable
	public Object doResolveDependency(DependencyDescriptor descriptor, @Nullable String beanName,
			@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) throws BeansException {
		// 
		InjectionPoint previousInjectionPoint = ConstructorResolver.setCurrentInjectionPoint(descriptor);
		try {
			Object shortcut = descriptor.resolveShortcut(this);
			if (shortcut != null) {
				return shortcut;
			}

			Class<?> type = descriptor.getDependencyType();
			// 用於支持spring的 @Value 註解
			Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);
			if (value != null) {
				if (value instanceof String) {
					String strVal = resolveEmbeddedValue((String) value);
					BeanDefinition bd = (beanName != null && containsBean(beanName) ?
							getMergedBeanDefinition(beanName) : null);
					value = evaluateBeanDefinitionString(strVal, bd);
				}
				// 通過轉換器將value的值轉換成對應的type類型
				TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
				try {
					return converter.convertIfNecessary(value, type, descriptor.getTypeDescriptor());
				}
				catch (UnsupportedOperationException ex) {
					// A custom TypeConverter which does not support TypeDescriptor resolution...
					return (descriptor.getField() != null ?
							converter.convertIfNecessary(value, type, descriptor.getField()) :
							converter.convertIfNecessary(value, type, descriptor.getMethodParameter()));
				}
			}
			// 屬性爲如 stream，array，collection，map
			Object multipleBeans = resolveMultipleBeans(descriptor, beanName, autowiredBeanNames, typeConverter);
			if (multipleBeans != null) {
				return multipleBeans;
			}
			// 查詢  autowire的屬性的候選者 
			Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
			if (matchingBeans.isEmpty()) {
				// 如果autowire的require屬性爲true而找到匹配項爲空，拋出異常
				if (isRequired(descriptor)) {
					raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
				}
				return null;
			}

			String autowiredBeanName;
			Object instanceCandidate;

			if (matchingBeans.size() > 1) {
				autowiredBeanName = determineAutowireCandidate(matchingBeans, descriptor);
				if (autowiredBeanName == null) {
					if (isRequired(descriptor) || !indicatesMultipleBeans(type)) {
						return descriptor.resolveNotUnique(descriptor.getResolvableType(), matchingBeans);
					}
					else {
						// In case of an optional Collection/Map, silently ignore a non-unique case:
						// possibly it was meant to be an empty collection of multiple regular beans
						// (before 4.3 in particular when we didn't even look for collection beans).
						return null;
					}
				}
				instanceCandidate = matchingBeans.get(autowiredBeanName);
			}
			else {
				// We have exactly one match.
				Map.Entry<String, Object> entry = matchingBeans.entrySet().iterator().next();
				autowiredBeanName = entry.getKey();
				instanceCandidate = entry.getValue();
			}

			if (autowiredBeanNames != null) {
				autowiredBeanNames.add(autowiredBeanName);
			}
			if (instanceCandidate instanceof Class) {
				instanceCandidate = descriptor.resolveCandidate(autowiredBeanName, type, this);
			}
			Object result = instanceCandidate;
			if (result instanceof NullBean) {
				if (isRequired(descriptor)) {
					raiseNoMatchingBeanFound(type, descriptor.getResolvableType(), descriptor);
				}
				result = null;
			}
			if (!ClassUtils.isAssignableValue(type, result)) {
				throw new BeanNotOfRequiredTypeException(autowiredBeanName, type, instanceCandidate.getClass());
			}
			return result;
		}
		finally {
			ConstructorResolver.setCurrentInjectionPoint(previousInjectionPoint);
		}
	}
	/**
     *  依賴注入屬性 Stream, array，Collection,Map 屬性注入
     */
	@Nullable
	private Object resolveMultipleBeans(DependencyDescriptor descriptor, @Nullable String beanName,
			@Nullable Set<String> autowiredBeanNames, @Nullable TypeConverter typeConverter) {

		final Class<?> type = descriptor.getDependencyType();
		// 屬性依賴是 stream類型
		if (descriptor instanceof StreamDependencyDescriptor) {
			Map<String, Object> matchingBeans = findAutowireCandidates(beanName, type, descriptor);
			if (autowiredBeanNames != null) {
				autowiredBeanNames.addAll(matchingBeans.keySet());
			}
			Stream<Object> stream = matchingBeans.keySet().stream()
					.map(name -> descriptor.resolveCandidate(name, type, this))
					.filter(bean -> !(bean instanceof NullBean));
			if (((StreamDependencyDescriptor) descriptor).isOrdered()) {
				stream = stream.sorted(adaptOrderComparator(matchingBeans));
			}
			return stream;
		}
		else if (type.isArray()) { // 屬性是數組類型
			Class<?> componentType = type.getComponentType();
			ResolvableType resolvableType = descriptor.getResolvableType();
			Class<?> resolvedArrayType = resolvableType.resolve(type);
			if (resolvedArrayType != type) {
				componentType = resolvableType.getComponentType().resolve();
			}
			if (componentType == null) {
				return null;
			}
			// 根據屬性類型找到beanFactory中所有類型的匹配bean
			//返回值的構成爲 ： key=匹配的 beanName，value=beanName 對應的實例化後的bean（通過getBean(beanName）返回)
			Map<String, Object> matchingBeans = findAutowireCandidates(beanName, componentType,
					new MultiElementDescriptor(descriptor));
			if (matchingBeans.isEmpty()) {
				return null;
			}
			if (autowiredBeanNames != null) {
				autowiredBeanNames.addAll(matchingBeans.keySet());
			}
			TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
			Object result = converter.convertIfNecessary(matchingBeans.values(), resolvedArrayType);
			if (result instanceof Object[]) {
				Comparator<Object> comparator = adaptDependencyComparator(matchingBeans);
				if (comparator != null) {
					Arrays.sort((Object[]) result, comparator);
				}
			}
			return result;
		}
		else if (Collection.class.isAssignableFrom(type) && type.isInterface()) { // 屬性爲 collection
	
			Class<?> elementType = descriptor.getResolvableType().asCollection().resolveGeneric();
			if (elementType == null) {
				return null;
			}
			Map<String, Object> matchingBeans = findAutowireCandidates(beanName, elementType,
					new MultiElementDescriptor(descriptor));
			if (matchingBeans.isEmpty()) {
				return null;
			}
			if (autowiredBeanNames != null) {
				autowiredBeanNames.addAll(matchingBeans.keySet());
			}
			TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter());
			Object result = converter.convertIfNecessary(matchingBeans.values(), type);
			if (result instanceof List) {
				Comparator<Object> comparator = adaptDependencyComparator(matchingBeans);
				if (comparator != null) {
					((List<?>) result).sort(comparator);
				}
			}
			return result;
		}
		else if (Map.class == type) { // 解析屬性屬於map類型
			ResolvableType mapType = descriptor.getResolvableType().asMap();
			Class<?> keyType = mapType.resolveGeneric(0);
			if (String.class != keyType) {
				return null;
			}
			Class<?> valueType = mapType.resolveGeneric(1);
			if (valueType == null) {
				return null;
			}
			Map<String, Object> matchingBeans = findAutowireCandidates(beanName, valueType,
					new MultiElementDescriptor(descriptor));
			if (matchingBeans.isEmpty()) {
				return null;
			}
			if (autowiredBeanNames != null) {
				autowiredBeanNames.addAll(matchingBeans.keySet());
			}
			return matchingBeans;
		}
		else {
			return null;
		}
	}
	// autowire的require屬性是否爲true
	private boolean isRequired(DependencyDescriptor descriptor) {
		return getAutowireCandidateResolver().isRequired(descriptor);
	}
	// 是否需要注入多個bean 的類型 
	private boolean indicatesMultipleBeans(Class<?> type) {
		return (type.isArray() || (type.isInterface() &&
				(Collection.class.isAssignableFrom(type) || Map.class.isAssignableFrom(type))));
	}
	@Nullable
	private Comparator<Object> adaptDependencyComparator(Map<String, ?> matchingBeans) {
		Comparator<Object> comparator = getDependencyComparator();
		if (comparator instanceof OrderComparator) {
			return ((OrderComparator) comparator).withSourceProvider(
					createFactoryAwareOrderSourceProvider(matchingBeans));
		}
		else {
			return comparator;
		}
	}
	private Comparator<Object> adaptOrderComparator(Map<String, ?> matchingBeans) {
		Comparator<Object> dependencyComparator = getDependencyComparator();
		OrderComparator comparator = (dependencyComparator instanceof OrderComparator ?
				(OrderComparator) dependencyComparator : OrderComparator.INSTANCE);
		return comparator.withSourceProvider(createFactoryAwareOrderSourceProvider(matchingBeans));
	}

	private OrderComparator.OrderSourceProvider createFactoryAwareOrderSourceProvider(Map<String, ?> beans) {
		IdentityHashMap<Object, String> instancesToBeanNames = new IdentityHashMap<>();
		beans.forEach((beanName, instance) -> instancesToBeanNames.put(instance, beanName));
		return new FactoryAwareOrderSourceProvider(instancesToBeanNames);
	}
	protected Map<String, Object> findAutowireCandidates(
			@Nullable String beanName, Class<?> requiredType, DependencyDescriptor descriptor) {

		String[] candidateNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(
				this, requiredType, true, descriptor.isEager());
		Map<String, Object> result = new LinkedHashMap<>(candidateNames.length);
		for (Map.Entry<Class<?>, Object> classObjectEntry : this.resolvableDependencies.entrySet()) {
			Class<?> autowiringType = classObjectEntry.getKey();
			if (autowiringType.isAssignableFrom(requiredType)) {
				Object autowiringValue = classObjectEntry.getValue();
				autowiringValue = AutowireUtils.resolveAutowiringValue(autowiringValue, requiredType);
				if (requiredType.isInstance(autowiringValue)) {
					result.put(ObjectUtils.identityToString(autowiringValue), autowiringValue);
					break;
				}
			}
		}
		for (String candidate : candidateNames) {
			if (!isSelfReference(beanName, candidate) && isAutowireCandidate(candidate, descriptor)) {
				addCandidateEntry(result, candidate, descriptor, requiredType);
			}
		}
		if (result.isEmpty()) {
			boolean multiple = indicatesMultipleBeans(requiredType);
			// Consider fallback matches if the first pass failed to find anything...
			DependencyDescriptor fallbackDescriptor = descriptor.forFallbackMatch();
			for (String candidate : candidateNames) {
				if (!isSelfReference(beanName, candidate) && isAutowireCandidate(candidate, fallbackDescriptor) &&
						(!multiple || getAutowireCandidateResolver().hasQualifier(descriptor))) {
					addCandidateEntry(result, candidate, descriptor, requiredType);
				}
			}
			if (result.isEmpty() && !multiple) {
				// Consider self references as a final pass...
				// but in the case of a dependency collection, not the very same bean itself.
				for (String candidate : candidateNames) {
					if (isSelfReference(beanName, candidate) &&
							(!(descriptor instanceof MultiElementDescriptor) || !beanName.equals(candidate)) &&
							isAutowireCandidate(candidate, fallbackDescriptor)) {
						addCandidateEntry(result, candidate, descriptor, requiredType);
					}
				}
			}
		}
		return result;
	}
	private void addCandidateEntry(Map<String, Object> candidates, String candidateName,
			DependencyDescriptor descriptor, Class<?> requiredType) {

		if (descriptor instanceof MultiElementDescriptor) {
			Object beanInstance = descriptor.resolveCandidate(candidateName, requiredType, this);
			if (!(beanInstance instanceof NullBean)) {
				candidates.put(candidateName, beanInstance);
			}
		}
		else if (containsSingleton(candidateName) || (descriptor instanceof StreamDependencyDescriptor &&
				((StreamDependencyDescriptor) descriptor).isOrdered())) {
			Object beanInstance = descriptor.resolveCandidate(candidateName, requiredType, this);
			candidates.put(candidateName, (beanInstance instanceof NullBean ? null : beanInstance));
		}
		else {
			candidates.put(candidateName, getType(candidateName));
		}
	}
	@Nullable // 偵測 依賴注入 候選者類型
	protected String determineAutowireCandidate(Map<String, Object> candidates, DependencyDescriptor descriptor) {
		Class<?> requiredType = descriptor.getDependencyType();
		String primaryCandidate = determinePrimaryCandidate(candidates, requiredType);
		if (primaryCandidate != null) {
			return primaryCandidate;
		}
		String priorityCandidate = determineHighestPriorityCandidate(candidates, requiredType);
		if (priorityCandidate != null) {
			return priorityCandidate;
		}
		// Fallback 失敗的兜底方法
		for (Map.Entry<String, Object> entry : candidates.entrySet()) {
			String candidateName = entry.getKey();
			Object beanInstance = entry.getValue();
			if ((beanInstance != null && this.resolvableDependencies.containsValue(beanInstance)) ||
					matchesBeanName(candidateName, descriptor.getDependencyName())) {
				return candidateName;
			}
		}
		return null;
	}

	@Nullable // 根據類型查找需要候選者的名稱
	protected String determinePrimaryCandidate(Map<String, Object> candidates, Class<?> requiredType) {
		String primaryBeanName = null;
		for (Map.Entry<String, Object> entry : candidates.entrySet()) {
			String candidateBeanName = entry.getKey();
			Object beanInstance = entry.getValue();
			if (isPrimary(candidateBeanName, beanInstance)) {
				if (primaryBeanName != null) {
					boolean candidateLocal = containsBeanDefinition(candidateBeanName);
					boolean primaryLocal = containsBeanDefinition(primaryBeanName);
					if (candidateLocal && primaryLocal) {
						throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(),
								"more than one 'primary' bean found among candidates: " + candidates.keySet());
					}
					else if (candidateLocal) {
						primaryBeanName = candidateBeanName;
					}
				}
				else {
					primaryBeanName = candidateBeanName;
				}
			}
		}
		return primaryBeanName;
	}


	@Nullable
	protected String determineHighestPriorityCandidate(Map<String, Object> candidates, Class<?> requiredType) {
		String highestPriorityBeanName = null;
		Integer highestPriority = null;
		for (Map.Entry<String, Object> entry : candidates.entrySet()) {
			String candidateBeanName = entry.getKey();
			Object beanInstance = entry.getValue();
			if (beanInstance != null) {
				Integer candidatePriority = getPriority(beanInstance);
				if (candidatePriority != null) {
					if (highestPriorityBeanName != null) {
						if (candidatePriority.equals(highestPriority)) {
							throw new NoUniqueBeanDefinitionException(requiredType, candidates.size(),
									"Multiple beans found with the same priority ('" + highestPriority +
									"') among candidates: " + candidates.keySet());
						}
						else if (candidatePriority < highestPriority) {
							highestPriorityBeanName = candidateBeanName;
							highestPriority = candidatePriority;
						}
					}
					else {
						highestPriorityBeanName = candidateBeanName;
						highestPriority = candidatePriority;
					}
				}
			}
		}
		return highestPriorityBeanName;
	}

	protected boolean isPrimary(String beanName, Object beanInstance) {
		String transformedBeanName = transformedBeanName(beanName);
		if (containsBeanDefinition(transformedBeanName)) {
			return getMergedLocalBeanDefinition(transformedBeanName).isPrimary();
		}
		BeanFactory parent = getParentBeanFactory();
		return (parent instanceof DefaultListableBeanFactory &&
				((DefaultListableBeanFactory) parent).isPrimary(transformedBeanName, beanInstance));
	}
	@Nullable
	protected Integer getPriority(Object beanInstance) {
		Comparator<Object> comparator = getDependencyComparator();
		if (comparator instanceof OrderComparator) {
			return ((OrderComparator) comparator).getPriority(beanInstance);
		}
		return null;
	}

	protected boolean matchesBeanName(String beanName, @Nullable String candidateName) {
		return (candidateName != null &&
				(candidateName.equals(beanName) || ObjectUtils.containsElement(getAliases(beanName), candidateName)));
	}
	private boolean isSelfReference(@Nullable String beanName, @Nullable String candidateName) {
		return (beanName != null && candidateName != null &&
				(beanName.equals(candidateName) || (containsBeanDefinition(candidateName) &&
						beanName.equals(getMergedLocalBeanDefinition(candidateName).getFactoryBeanName()))));
	}

	private void raiseNoMatchingBeanFound(
			Class<?> type, ResolvableType resolvableType, DependencyDescriptor descriptor) throws BeansException {

		checkBeanNotOfRequiredType(type, descriptor);

		throw new NoSuchBeanDefinitionException(resolvableType,
				"expected at least 1 bean which qualifies as autowire candidate. " +
				"Dependency annotations: " + ObjectUtils.nullSafeToString(descriptor.getAnnotations()));
	}
	private void checkBeanNotOfRequiredType(Class<?> type, DependencyDescriptor descriptor) {
		for (String beanName : this.beanDefinitionNames) {
			RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
			Class<?> targetType = mbd.getTargetType();
			if (targetType != null && type.isAssignableFrom(targetType) &&
					isAutowireCandidate(beanName, mbd, descriptor, getAutowireCandidateResolver())) {
				// Probably a proxy interfering with target type match -> throw meaningful exception.
				Object beanInstance = getSingleton(beanName, false);
				Class<?> beanType = (beanInstance != null && beanInstance.getClass() != NullBean.class ?
						beanInstance.getClass() : predictBeanType(beanName, mbd));
				if (beanType != null && !type.isAssignableFrom(beanType)) {
					throw new BeanNotOfRequiredTypeException(beanName, type, beanType);
				}
			}
		}

		BeanFactory parent = getParentBeanFactory();
		if (parent instanceof DefaultListableBeanFactory) {
			((DefaultListableBeanFactory) parent).checkBeanNotOfRequiredType(type, descriptor);
		}
	}
    // 解析  依賴注入 Optional類型
	private Optional<?> createOptionalDependency(
			DependencyDescriptor descriptor, @Nullable String beanName, final Object... args) {

		DependencyDescriptor descriptorToUse = new NestedDependencyDescriptor(descriptor) {
			@Override
			public boolean isRequired() {
				return false;
			}
			@Override
			public Object resolveCandidate(String beanName, Class<?> requiredType, BeanFactory beanFactory) {
				return (!ObjectUtils.isEmpty(args) ? beanFactory.getBean(beanName, args) :
						super.resolveCandidate(beanName, requiredType, beanFactory));
			}
		};
		Object result = doResolveDependency(descriptorToUse, beanName, null, null);
		return (result instanceof Optional ? (Optional<?>) result : Optional.ofNullable(result));
	}

	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder(ObjectUtils.identityToString(this));
		sb.append(": defining beans [");
		sb.append(StringUtils.collectionToCommaDelimitedString(this.beanDefinitionNames));
		sb.append("]; ");
		BeanFactory parent = getParentBeanFactory();
		if (parent == null) {
			sb.append("root of factory hierarchy");
		}
		else {
			sb.append("parent: ").append(ObjectUtils.identityToString(parent));
		}
		return sb.toString();
	}


	//---------------------------------------------------------------------
	// Serialization support  x
	//---------------------------------------------------------------------

	private void readObject(ObjectInputStream ois) throws IOException, ClassNotFoundException {
		throw new NotSerializableException("DefaultListableBeanFactory itself is not deserializable - " +
				"just a SerializedBeanFactoryReference is");
	}

	protected Object writeReplace() throws ObjectStreamException {
		if (this.serializationId != null) {
			return new SerializedBeanFactoryReference(this.serializationId);
		}
		else {
			throw new NotSerializableException("DefaultListableBeanFactory has no serialization id");
		}
	}


	/**
	 * Minimal id reference to the factory.
	 * Resolved to the actual factory instance on deserialization.
	 */
	private static class SerializedBeanFactoryReference implements Serializable {

		private final String id;

		public SerializedBeanFactoryReference(String id) {
			this.id = id;
		}

		private Object readResolve() {
			Reference<?> ref = serializableFactories.get(this.id);
			if (ref != null) {
				Object result = ref.get();
				if (result != null) {
					return result;
				}
			}
			// Lenient fallback: dummy factory in case of original factory not found...
			DefaultListableBeanFactory dummyFactory = new DefaultListableBeanFactory();
			dummyFactory.serializationId = this.id;
			return dummyFactory;
		}
	}


	/**
	 * A dependency descriptor marker for nested elements.
	 */
	private static class NestedDependencyDescriptor extends DependencyDescriptor {

		public NestedDependencyDescriptor(DependencyDescriptor original) {
			super(original);
			increaseNestingLevel();
		}
	}


	/**
	 * A dependency descriptor for a multi-element declaration with nested elements.
	 */
	private static class MultiElementDescriptor extends NestedDependencyDescriptor {

		public MultiElementDescriptor(DependencyDescriptor original) {
			super(original);
		}
	}


	/**
	 * A dependency descriptor marker for stream access to multiple elements.
	 */
	private static class StreamDependencyDescriptor extends DependencyDescriptor {

		private final boolean ordered;

		public StreamDependencyDescriptor(DependencyDescriptor original, boolean ordered) {
			super(original);
			this.ordered = ordered;
		}

		public boolean isOrdered() {
			return this.ordered;
		}
	}


	private interface BeanObjectProvider<T> extends ObjectProvider<T>, Serializable {
	}


	/**
	 * Serializable ObjectFactory/ObjectProvider for lazy resolution of a dependency.
	 */
	private class DependencyObjectProvider implements BeanObjectProvider<Object> {

		private final DependencyDescriptor descriptor;

		private final boolean optional;

		@Nullable
		private final String beanName;

		public DependencyObjectProvider(DependencyDescriptor descriptor, @Nullable String beanName) {
			this.descriptor = new NestedDependencyDescriptor(descriptor);
			this.optional = (this.descriptor.getDependencyType() == Optional.class);
			this.beanName = beanName;
		}

		@Override
		public Object getObject() throws BeansException {
			if (this.optional) {
				return createOptionalDependency(this.descriptor, this.beanName);
			}
			else {
				Object result = doResolveDependency(this.descriptor, this.beanName, null, null);
				if (result == null) {
					throw new NoSuchBeanDefinitionException(this.descriptor.getResolvableType());
				}
				return result;
			}
		}

		@Override
		public Object getObject(final Object... args) throws BeansException {
			if (this.optional) {
				return createOptionalDependency(this.descriptor, this.beanName, args);
			}
			else {
				DependencyDescriptor descriptorToUse = new DependencyDescriptor(this.descriptor) {
					@Override
					public Object resolveCandidate(String beanName, Class<?> requiredType, BeanFactory beanFactory) {
						return beanFactory.getBean(beanName, args);
					}
				};
				Object result = doResolveDependency(descriptorToUse, this.beanName, null, null);
				if (result == null) {
					throw new NoSuchBeanDefinitionException(this.descriptor.getResolvableType());
				}
				return result;
			}
		}

		@Override
		@Nullable
		public Object getIfAvailable() throws BeansException {
			if (this.optional) {
				return createOptionalDependency(this.descriptor, this.beanName);
			}
			else {
				DependencyDescriptor descriptorToUse = new DependencyDescriptor(this.descriptor) {
					@Override
					public boolean isRequired() {
						return false;
					}
				};
				return doResolveDependency(descriptorToUse, this.beanName, null, null);
			}
		}

		@Override
		@Nullable
		public Object getIfUnique() throws BeansException {
			DependencyDescriptor descriptorToUse = new DependencyDescriptor(this.descriptor) {
				@Override
				public boolean isRequired() {
					return false;
				}
				@Override
				@Nullable
				public Object resolveNotUnique(ResolvableType type, Map<String, Object> matchingBeans) {
					return null;
				}
			};
			if (this.optional) {
				return createOptionalDependency(descriptorToUse, this.beanName);
			}
			else {
				return doResolveDependency(descriptorToUse, this.beanName, null, null);
			}
		}

		@Nullable
		protected Object getValue() throws BeansException {
			if (this.optional) {
				return createOptionalDependency(this.descriptor, this.beanName);
			}
			else {
				return doResolveDependency(this.descriptor, this.beanName, null, null);
			}
		}

		@Override
		public Stream<Object> stream() {
			return resolveStream(false);
		}

		@Override
		public Stream<Object> orderedStream() {
			return resolveStream(true);
		}

		@SuppressWarnings("unchecked")
		private Stream<Object> resolveStream(boolean ordered) {
			DependencyDescriptor descriptorToUse = new StreamDependencyDescriptor(this.descriptor, ordered);
			Object result = doResolveDependency(descriptorToUse, this.beanName, null, null);
			return (result instanceof Stream ? (Stream<Object>) result : Stream.of(result));
		}
	}


	/**
	 * Separate inner class for avoiding a hard dependency on the {@code javax.inject} API.
	 * Actual {@code javax.inject.Provider} implementation is nested here in order to make it
	 * invisible for Graal's introspection of DefaultListableBeanFactory's nested classes.
	 */
	private class Jsr330Factory implements Serializable {

		public Object createDependencyProvider(DependencyDescriptor descriptor, @Nullable String beanName) {
			return new Jsr330Provider(descriptor, beanName);
		}

		private class Jsr330Provider extends DependencyObjectProvider implements Provider<Object> {

			public Jsr330Provider(DependencyDescriptor descriptor, @Nullable String beanName) {
				super(descriptor, beanName);
			}

			@Override
			@Nullable
			public Object get() throws BeansException {
				return getValue();
			}
		}
	}


	/**
	 * An {@link org.springframework.core.OrderComparator.OrderSourceProvider} implementation
	 * that is aware of the bean metadata of the instances to sort.
	 * <p>Lookup for the method factory of an instance to sort, if any, and let the
	 * comparator retrieve the {@link org.springframework.core.annotation.Order}
	 * value defined on it. This essentially allows for the following construct:
	 */
	private class FactoryAwareOrderSourceProvider implements OrderComparator.OrderSourceProvider {

		private final Map<Object, String> instancesToBeanNames;

		public FactoryAwareOrderSourceProvider(Map<Object, String> instancesToBeanNames) {
			this.instancesToBeanNames = instancesToBeanNames;
		}

		@Override
		@Nullable
		public Object getOrderSource(Object obj) {
			String beanName = this.instancesToBeanNames.get(obj);
			if (beanName == null || !containsBeanDefinition(beanName)) {
				return null;
			}
			RootBeanDefinition beanDefinition = getMergedLocalBeanDefinition(beanName);
			List<Object> sources = new ArrayList<>(2);
			Method factoryMethod = beanDefinition.getResolvedFactoryMethod();
			if (factoryMethod != null) {
				sources.add(factoryMethod);
			}
			Class<?> targetType = beanDefinition.getTargetType();
			if (targetType != null && targetType != obj.getClass()) {
				sources.add(targetType);
			}
			return sources.toArray();
		}
	}

}

AutowireCandidateResolver

AutowireCandidateResolver autowire候選解析接口，解析標記@autowire的bean注入那個bean

public interface AutowireCandidateResolver {
	default boolean isAutowireCandidate(BeanDefinitionHolder bdHolder, DependencyDescriptor descriptor) {
		return bdHolder.getBeanDefinition().isAutowireCandidate();
	}
	default boolean isRequired(DependencyDescriptor descriptor) {
		return descriptor.isRequired();
	}
	default boolean hasQualifier(DependencyDescriptor descriptor) {
		return false;
	}
	@Nullable
	default Object getSuggestedValue(DependencyDescriptor descriptor) {
		return null;
	}
	@Nullable
	default Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, @Nullable String beanName) {
		return null;
	}
}

SimpleAutowireCandidateResolver 簡單實現
GenericTypeAwareAutowireCandidateResolver 通用設置 注入了BeanFactory

public class GenericTypeAwareAutowireCandidateResolver extends SimpleAutowireCandidateResolver
		implements BeanFactoryAware {
	@Nullable
	private BeanFactory beanFactory;
	@Override
	public void setBeanFactory(BeanFactory beanFactory) {
		this.beanFactory = beanFactory;
	}
	@Nullable
	protected final BeanFactory getBeanFactory() {
		return this.beanFactory;
	}
	@Override
	public boolean isAutowireCandidate(BeanDefinitionHolder bdHolder, DependencyDescriptor descriptor) {
		if (!super.isAutowireCandidate(bdHolder, descriptor)) {
			// If explicitly false, do not proceed with any other checks...
			return false;
		}
		return checkGenericTypeMatch(bdHolder, descriptor);
	}
	/**
	 * Match the given dependency type with its generic type information against the given
	 * candidate bean definition.
	 */
	protected boolean checkGenericTypeMatch(BeanDefinitionHolder bdHolder, DependencyDescriptor descriptor) {
		ResolvableType dependencyType = descriptor.getResolvableType();
		if (dependencyType.getType() instanceof Class) {
			// No generic type -> we know it's a Class type-match, so no need to check again.
			return true;
		}
		ResolvableType targetType = null;
		boolean cacheType = false;
		RootBeanDefinition rbd = null;
		if (bdHolder.getBeanDefinition() instanceof RootBeanDefinition) {
			rbd = (RootBeanDefinition) bdHolder.getBeanDefinition();
		}
		if (rbd != null) {
			targetType = rbd.targetType;
			if (targetType == null) {
				cacheType = true;
				// First, check factory method return type, if applicable
				targetType = getReturnTypeForFactoryMethod(rbd, descriptor);
				if (targetType == null) {
					RootBeanDefinition dbd = getResolvedDecoratedDefinition(rbd);
					if (dbd != null) {
						targetType = dbd.targetType;
						if (targetType == null) {
							targetType = getReturnTypeForFactoryMethod(dbd, descriptor);
						}
					}
				}
			}
		}
		if (targetType == null) {
			// Regular case: straight bean instance, with BeanFactory available.
			if (this.beanFactory != null) {
				Class<?> beanType = this.beanFactory.getType(bdHolder.getBeanName());
				if (beanType != null) {
					targetType = ResolvableType.forClass(ClassUtils.getUserClass(beanType));
				}
			}
			// Fallback: no BeanFactory set, or no type resolvable through it
			// -> best-effort match against the target class if applicable.
			if (targetType == null && rbd != null && rbd.hasBeanClass() && rbd.getFactoryMethodName() == null) {
				Class<?> beanClass = rbd.getBeanClass();
				if (!FactoryBean.class.isAssignableFrom(beanClass)) {
					targetType = ResolvableType.forClass(ClassUtils.getUserClass(beanClass));
				}
			}
		}

		if (targetType == null) {
			return true;
		}
		if (cacheType) {
			rbd.targetType = targetType;
		}
		if (descriptor.fallbackMatchAllowed() &&
				(targetType.hasUnresolvableGenerics() || targetType.resolve() == Properties.class)) {
			// Fallback matches allow unresolvable generics, e.g. plain HashMap to Map<String,String>;
			// and pragmatically also java.util.Properties to any Map (since despite formally being a
			// Map<Object,Object>, java.util.Properties is usually perceived as a Map<String,String>).
			return true;
		}
		// Full check for complex generic type match...
		return dependencyType.isAssignableFrom(targetType);
	}
	@Nullable
	protected RootBeanDefinition getResolvedDecoratedDefinition(RootBeanDefinition rbd) {
		BeanDefinitionHolder decDef = rbd.getDecoratedDefinition();
		if (decDef != null && this.beanFactory instanceof ConfigurableListableBeanFactory) {
			ConfigurableListableBeanFactory clbf = (ConfigurableListableBeanFactory) this.beanFactory;
			if (clbf.containsBeanDefinition(decDef.getBeanName())) {
				BeanDefinition dbd = clbf.getMergedBeanDefinition(decDef.getBeanName());
				if (dbd instanceof RootBeanDefinition) {
					return (RootBeanDefinition) dbd;
				}
			}
		}
		return null;
	}
	@Nullable
	protected ResolvableType getReturnTypeForFactoryMethod(RootBeanDefinition rbd, DependencyDescriptor descriptor) {
		// Should typically be set for any kind of factory method, since the BeanFactory
		// pre-resolves them before reaching out to the AutowireCandidateResolver...
		ResolvableType returnType = rbd.factoryMethodReturnType;
		if (returnType == null) {
			Method factoryMethod = rbd.getResolvedFactoryMethod();
			if (factoryMethod != null) {
				returnType = ResolvableType.forMethodReturnType(factoryMethod);
			}
		}
		if (returnType != null) {
			Class<?> resolvedClass = returnType.resolve();
			if (resolvedClass != null && descriptor.getDependencyType().isAssignableFrom(resolvedClass)) {
				// Only use factory method metadata if the return type is actually expressive enough
				// for our dependency. Otherwise, the returned instance type may have matched instead
				// in case of a singleton instance having been registered with the container already.
				return returnType;
			}
		}
		return null;
	}
}

QualifierAnnotationAutowireCandidateResolver 支持解析@Qualifier和@Value

public class QualifierAnnotationAutowireCandidateResolver extends GenericTypeAwareAutowireCandidateResolver {

	private final Set<Class<? extends Annotation>> qualifierTypes = new LinkedHashSet<>(2);

	private Class<? extends Annotation> valueAnnotationType = Value.class;
	@SuppressWarnings("unchecked")
	// 默認支持解析org.springframework.beans.factory.annotation.Qualifier和javax.inject.Qualifier
	public QualifierAnnotationAutowireCandidateResolver() {
		this.qualifierTypes.add(Qualifier.class);
		try {
			this.qualifierTypes.add((Class<? extends Annotation>) ClassUtils.forName("javax.inject.Qualifier",
							QualifierAnnotationAutowireCandidateResolver.class.getClassLoader()));
		}
		catch (ClassNotFoundException ex) {
			// JSR-330 API not available - simply skip.
		}
	}
	// 參數構造 
	public QualifierAnnotationAutowireCandidateResolver(Class<? extends Annotation> qualifierType) {
		Assert.notNull(qualifierType, "'qualifierType' must not be null");
		this.qualifierTypes.add(qualifierType);
	}
	public QualifierAnnotationAutowireCandidateResolver(Set<Class<? extends Annotation>> qualifierTypes) {
		Assert.notNull(qualifierTypes, "'qualifierTypes' must not be null");
		this.qualifierTypes.addAll(qualifierTypes);
	}
	public void addQualifierType(Class<? extends Annotation> qualifierType) {
		this.qualifierTypes.add(qualifierType);
	}
	// 
	public void setValueAnnotationType(Class<? extends Annotation> valueAnnotationType) {
		this.valueAnnotationType = valueAnnotationType;
	}
	// 判斷提供 bdHolder 是否是 Qualifier 候選
	@Override
	public boolean isAutowireCandidate(BeanDefinitionHolder bdHolder, DependencyDescriptor descriptor) {
		boolean match = super.isAutowireCandidate(bdHolder, descriptor);
		if (match) {
			match = checkQualifiers(bdHolder, descriptor.getAnnotations());
			if (match) {
				MethodParameter methodParam = descriptor.getMethodParameter();
				if (methodParam != null) {
					Method method = methodParam.getMethod();
					if (method == null || void.class == method.getReturnType()) {
						match = checkQualifiers(bdHolder, methodParam.getMethodAnnotations());
					}
				}
			}
		}
		return match;
	}
	/**
	 * Match the given qualifier annotations against the candidate bean definition.
	 */
	protected boolean checkQualifiers(BeanDefinitionHolder bdHolder, Annotation[] annotationsToSearch) {
		if (ObjectUtils.isEmpty(annotationsToSearch)) {
			return true;
		}
		SimpleTypeConverter typeConverter = new SimpleTypeConverter();
		for (Annotation annotation : annotationsToSearch) {
			Class<? extends Annotation> type = annotation.annotationType();
			boolean checkMeta = true;
			boolean fallbackToMeta = false;
			if (isQualifier(type)) {
				if (!checkQualifier(bdHolder, annotation, typeConverter)) {
					fallbackToMeta = true;
				}
				else {
					checkMeta = false;
				}
			}
			if (checkMeta) {
				boolean foundMeta = false;
				for (Annotation metaAnn : type.getAnnotations()) {
					Class<? extends Annotation> metaType = metaAnn.annotationType();
					if (isQualifier(metaType)) {
						foundMeta = true;
						// Only accept fallback match if @Qualifier annotation has a value...
						// Otherwise it is just a marker for a custom qualifier annotation.
						if ((fallbackToMeta && StringUtils.isEmpty(AnnotationUtils.getValue(metaAnn))) ||
								!checkQualifier(bdHolder, metaAnn, typeConverter)) {
							return false;
						}
					}
				}
				if (fallbackToMeta && !foundMeta) {
					return false;
				}
			}
		}
		return true;
	}
	// 檢查給定的註釋類型是否是可識別的限定符類型(Qualifier)
	protected boolean isQualifier(Class<? extends Annotation> annotationType) {
		for (Class<? extends Annotation> qualifierType : this.qualifierTypes) {
			if (annotationType.equals(qualifierType) || annotationType.isAnnotationPresent(qualifierType)) {
				return true;
			}
		}
		return false;
	}
	/**
	 * Match the given qualifier annotation against the candidate bean definition.
	 */
	protected boolean checkQualifier(
			BeanDefinitionHolder bdHolder, Annotation annotation, TypeConverter typeConverter) {
		// 註釋類型
		Class<? extends Annotation> type = annotation.annotationType();
		RootBeanDefinition bd = (RootBeanDefinition) bdHolder.getBeanDefinition();
		// 獲取bd定義上的  qualifier  候選
		AutowireCandidateQualifier qualifier = bd.getQualifier(type.getName());
		if (qualifier == null) {
			qualifier = bd.getQualifier(ClassUtils.getShortName(type));
		}
		if (qualifier == null) {
			// First, check annotation on qualified element, if any
			Annotation targetAnnotation = getQualifiedElementAnnotation(bd, type);
			// Then, check annotation on factory method, if applicable
			if (targetAnnotation == null) {
				targetAnnotation = getFactoryMethodAnnotation(bd, type);
			}
			if (targetAnnotation == null) {
				RootBeanDefinition dbd = getResolvedDecoratedDefinition(bd);
				if (dbd != null) {
					targetAnnotation = getFactoryMethodAnnotation(dbd, type);
				}
			}
			if (targetAnnotation == null) {
				// Look for matching annotation on the target class
				if (getBeanFactory() != null) {
					try {
						Class<?> beanType = getBeanFactory().getType(bdHolder.getBeanName());
						if (beanType != null) {
							targetAnnotation = AnnotationUtils.getAnnotation(ClassUtils.getUserClass(beanType), type);
						}
					}
					catch (NoSuchBeanDefinitionException ex) {
						// Not the usual case - simply forget about the type check...
					}
				}
				if (targetAnnotation == null && bd.hasBeanClass()) {
					targetAnnotation = AnnotationUtils.getAnnotation(ClassUtils.getUserClass(bd.getBeanClass()), type);
				}
			}
			if (targetAnnotation != null && targetAnnotation.equals(annotation)) {
				return true;
			}
		}

		Map<String, Object> attributes = AnnotationUtils.getAnnotationAttributes(annotation);
		if (attributes.isEmpty() && qualifier == null) {
			// If no attributes, the qualifier must be present
			return false;
		}
		for (Map.Entry<String, Object> entry : attributes.entrySet()) {
			String attributeName = entry.getKey();
			Object expectedValue = entry.getValue();
			Object actualValue = null;
			// Check qualifier first
			if (qualifier != null) {
				actualValue = qualifier.getAttribute(attributeName);
			}
			if (actualValue == null) {
				// Fall back on bean definition attribute
				actualValue = bd.getAttribute(attributeName);
			}
			if (actualValue == null && attributeName.equals(AutowireCandidateQualifier.VALUE_KEY) &&
					expectedValue instanceof String && bdHolder.matchesName((String) expectedValue)) {
				// Fall back on bean name (or alias) match
				continue;
			}
			if (actualValue == null && qualifier != null) {
				// Fall back on default, but only if the qualifier is present
				actualValue = AnnotationUtils.getDefaultValue(annotation, attributeName);
			}
			if (actualValue != null) {
				actualValue = typeConverter.convertIfNecessary(actualValue, expectedValue.getClass());
			}
			if (!expectedValue.equals(actualValue)) {
				return false;
			}
		}
		return true;
	}

	@Nullable
	protected Annotation getQualifiedElementAnnotation(RootBeanDefinition bd, Class<? extends Annotation> type) {
		AnnotatedElement qualifiedElement = bd.getQualifiedElement();
		return (qualifiedElement != null ? AnnotationUtils.getAnnotation(qualifiedElement, type) : null);
	}

	@Nullable
	protected Annotation getFactoryMethodAnnotation(RootBeanDefinition bd, Class<? extends Annotation> type) {
		Method resolvedFactoryMethod = bd.getResolvedFactoryMethod();
		return (resolvedFactoryMethod != null ? AnnotationUtils.getAnnotation(resolvedFactoryMethod, type) : null);
	}


	/**
	 * Determine whether the given dependency declares an autowired annotation,
	 * checking its required flag.
	 * @see Autowired#required()
	 */
	@Override
	public boolean isRequired(DependencyDescriptor descriptor) {
		if (!super.isRequired(descriptor)) {
			return false;
		}
		Autowired autowired = descriptor.getAnnotation(Autowired.class);
		return (autowired == null || autowired.required());
	}

	/**
	 * Determine whether the given dependency declares a qualifier annotation.
	 * @see #isQualifier(Class)
	 * @see Qualifier
	 */
	@Override
	public boolean hasQualifier(DependencyDescriptor descriptor) {
		for (Annotation ann : descriptor.getAnnotations()) {
			if (isQualifier(ann.annotationType())) {
				return true;
			}
		}
		return false;
	}

	/**
	 * Determine whether the given dependency declares a value annotation.
	 * @see Value
	 */
	@Override
	@Nullable
	public Object getSuggestedValue(DependencyDescriptor descriptor) {
		Object value = findValue(descriptor.getAnnotations());
		if (value == null) {
			MethodParameter methodParam = descriptor.getMethodParameter();
			if (methodParam != null) {
				value = findValue(methodParam.getMethodAnnotations());
			}
		}
		return value;
	}

	/**
	 * Determine a suggested value from any of the given candidate annotations.
	 */
	@Nullable
	protected Object findValue(Annotation[] annotationsToSearch) {
		if (annotationsToSearch.length > 0) {   // qualifier annotations have to be local
			AnnotationAttributes attr = AnnotatedElementUtils.getMergedAnnotationAttributes(
					AnnotatedElementUtils.forAnnotations(annotationsToSearch), this.valueAnnotationType);
			if (attr != null) {
				return extractValue(attr);
			}
		}
		return null;
	}
	// 解析 提取註解中的value值 如@Qualifier("imp")->imp
	protected Object extractValue(AnnotationAttributes attr) {
		Object value = attr.get(AnnotationUtils.VALUE);
		if (value == null) {
			throw new IllegalStateException("Value annotation must have a value attribute");
		}
		return value;
	}
}

ContextAnnotationAutowireCandidateResolver 解析候選者策略 @lazy

public class ContextAnnotationAutowireCandidateResolver extends QualifierAnnotationAutowireCandidateResolver {
	@Override
	@Nullable
	public Object getLazyResolutionProxyIfNecessary(DependencyDescriptor descriptor, @Nullable String beanName) {
		return (isLazy(descriptor) ? buildLazyResolutionProxy(descriptor, beanName) : null);
	}
	// 是否有@Lazy 標記
	protected boolean isLazy(DependencyDescriptor descriptor) {
		for (Annotation ann : descriptor.getAnnotations()) {
			Lazy lazy = AnnotationUtils.getAnnotation(ann, Lazy.class);
			if (lazy != null && lazy.value()) {
				return true;
			}
		}
		MethodParameter methodParam = descriptor.getMethodParameter();
		if (methodParam != null) {
			Method method = methodParam.getMethod();
			if (method == null || void.class == method.getReturnType()) {
				Lazy lazy = AnnotationUtils.getAnnotation(methodParam.getAnnotatedElement(), Lazy.class);
				if (lazy != null && lazy.value()) {
					return true;
				}
			}
		}
		return false;
	}
	// bulid一個lazy的bean的代理 解決循環引用
	protected Object buildLazyResolutionProxy(final DependencyDescriptor descriptor, final @Nullable String beanName) {
		Assert.state(getBeanFactory() instanceof DefaultListableBeanFactory,
				"BeanFactory needs to be a DefaultListableBeanFactory");
		final DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) getBeanFactory();
		TargetSource ts = new TargetSource() {
			@Override
			public Class<?> getTargetClass() {
				return descriptor.getDependencyType();
			}
			@Override
			public boolean isStatic() {
				return false;
			}
			@Override
			public Object getTarget() { 
				Object target = beanFactory.doResolveDependency(descriptor, beanName, null, null);
				// 如果bean還未實例化 ，先給一個空實現替代
				if (target == null) {
					Class<?> type = getTargetClass();
					if (Map.class == type) {
						return Collections.emptyMap();
					}
					else if (List.class == type) {
						return Collections.emptyList();
					}
					else if (Set.class == type || Collection.class == type) {
						return Collections.emptySet();
					}
					throw new NoSuchBeanDefinitionException(descriptor.getResolvableType(),
							"Optional dependency not present for lazy injection point");
				}
				return target;
			}
			@Override
			public void releaseTarget(Object target) {
			}
		};
		ProxyFactory pf = new ProxyFactory();
		pf.setTargetSource(ts);
		Class<?> dependencyType = descriptor.getDependencyType();
		if (dependencyType.isInterface()) {
			pf.addInterface(dependencyType);
		}
		return pf.getProxy(beanFactory.getBeanClassLoader());
	}
}