SpringBoot启动的默认BeanFactory：DefaultListableBeanFactory

成员

// 自身定义
@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. */
	private boolean allowBeanDefinitionOverriding = true;

	/** Whether to allow eager class loading even for lazy-init beans. */
	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. */
	private AutowireCandidateResolver autowireCandidateResolver = new SimpleAutowireCandidateResolver();

	/** Map from dependency type to corresponding autowired value. */
	private final Map<Class<?>, Object> resolvableDependencies = new ConcurrentHashMap<>(16);

	/** Map of bean definition objects, keyed by bean name. */
	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. */
	private volatile List<String> beanDefinitionNames = new ArrayList<>(256);
//
	/** List of names of manually registered singletons, in registration order. */
	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;

//继承自AbstractAutowireCapableBeanFactory
	/** Strategy for creating bean instances. */
	private InstantiationStrategy instantiationStrategy = new CglibSubclassingInstantiationStrategy();

	/** Resolver strategy for method parameter names. */
	@Nullable
	private ParameterNameDiscoverer parameterNameDiscoverer = new DefaultParameterNameDiscoverer();

	/** Whether to automatically try to resolve circular references between beans. */
	private boolean allowCircularReferences = true;

	/**
	 * Whether to resort to injecting a raw bean instance in case of circular reference,
	 * even if the injected bean eventually got wrapped.
	 */
	private boolean allowRawInjectionDespiteWrapping = false;

	/**
	 * Dependency types to ignore on dependency check and autowire, as Set of
	 * Class objects: for example, String. Default is none.
	 */
	private final Set<Class<?>> ignoredDependencyTypes = new HashSet<>();

	/**
	 * Dependency interfaces to ignore on dependency check and autowire, as Set of
	 * Class objects. By default, only the BeanFactory interface is ignored.
	 */
	private final Set<Class<?>> ignoredDependencyInterfaces = new HashSet<>();

	/**
	 * The name of the currently created bean, for implicit dependency registration
	 * on getBean etc invocations triggered from a user-specified Supplier callback.
	 */
	private final NamedThreadLocal<String> currentlyCreatedBean = new NamedThreadLocal<>("Currently created bean");

	/** Cache of unfinished FactoryBean instances: FactoryBean name to BeanWrapper. */
	private final ConcurrentMap<String, BeanWrapper> factoryBeanInstanceCache = new ConcurrentHashMap<>();

	/** Cache of candidate factory methods per factory class. */
	private final ConcurrentMap<Class<?>, Method[]> factoryMethodCandidateCache = new ConcurrentHashMap<>();

	/** Cache of filtered PropertyDescriptors: bean Class to PropertyDescriptor array. */
	private final ConcurrentMap<Class<?>, PropertyDescriptor[]> filteredPropertyDescriptorsCache =
			new ConcurrentHashMap<>();
//继承自AbstractBeanFactory
	/** Parent bean factory, for bean inheritance support. */
	@Nullable
	private BeanFactory parentBeanFactory;

	/** ClassLoader to resolve bean class names with, if necessary. */
	@Nullable
	private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();

	/** ClassLoader to temporarily resolve bean class names with, if necessary. */
	@Nullable
	private ClassLoader tempClassLoader;

	/** Whether to cache bean metadata or rather reobtain it for every access. */
	private boolean cacheBeanMetadata = true;

	/** Resolution strategy for expressions in bean definition values. */
	@Nullable
	private BeanExpressionResolver beanExpressionResolver;

	/** Spring ConversionService to use instead of PropertyEditors. */
	@Nullable
	private ConversionService conversionService;

	/** Custom PropertyEditorRegistrars to apply to the beans of this factory. */
	private final Set<PropertyEditorRegistrar> propertyEditorRegistrars = new LinkedHashSet<>(4);

	/** Custom PropertyEditors to apply to the beans of this factory. */
	private final Map<Class<?>, Class<? extends PropertyEditor>> customEditors = new HashMap<>(4);

	/** A custom TypeConverter to use, overriding the default PropertyEditor mechanism. */
	@Nullable
	private TypeConverter typeConverter;

	/** String resolvers to apply e.g. to annotation attribute values. */
	private final List<StringValueResolver> embeddedValueResolvers = new CopyOnWriteArrayList<>();

	/** BeanPostProcessors to apply in createBean. */
	private final List<BeanPostProcessor> beanPostProcessors = new CopyOnWriteArrayList<>();

	/** Indicates whether any InstantiationAwareBeanPostProcessors have been registered. */
	private volatile boolean hasInstantiationAwareBeanPostProcessors;

	/** Indicates whether any DestructionAwareBeanPostProcessors have been registered. */
	private volatile boolean hasDestructionAwareBeanPostProcessors;

	/** Map from scope identifier String to corresponding Scope. */
	private final Map<String, Scope> scopes = new LinkedHashMap<>(8);

	/** Security context used when running with a SecurityManager. */
	@Nullable
	private SecurityContextProvider securityContextProvider;

	/** Map from bean name to merged RootBeanDefinition. */
	private final Map<String, RootBeanDefinition> mergedBeanDefinitions = new ConcurrentHashMap<>(256);

	/** Names of beans that have already been created at least once. */
	private final Set<String> alreadyCreated = Collections.newSetFromMap(new ConcurrentHashMap<>(256));

	/** Names of beans that are currently in creation. */
	private final ThreadLocal<Object> prototypesCurrentlyInCreation =
			new NamedThreadLocal<>("Prototype beans currently in creation");

//继承自FactoryBeanRegistrySupport
	/** Cache of singleton objects created by FactoryBeans: FactoryBean name to object. */
	private final Map<String, Object> factoryBeanObjectCache = new ConcurrentHashMap<>(16);

//继承自DefaultSingletonBeanRegistry
	/** Cache of singleton objects: bean name to bean instance. */
	private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);

	/** Cache of singleton factories: bean name to ObjectFactory. */
	private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);

	/** Cache of early singleton objects: bean name to bean instance. */
	private final Map<String, Object> earlySingletonObjects = new HashMap<>(16);

	/** Set of registered singletons, containing the bean names in registration order. */
	private final Set<String> registeredSingletons = new LinkedHashSet<>(256);

	/** Names of beans that are currently in creation. */
	private final Set<String> singletonsCurrentlyInCreation =
			Collections.newSetFromMap(new ConcurrentHashMap<>(16));

	/** Names of beans currently excluded from in creation checks. */
	private final Set<String> inCreationCheckExclusions =
			Collections.newSetFromMap(new ConcurrentHashMap<>(16));

	/** List of suppressed Exceptions, available for associating related causes. */
	@Nullable
	private Set<Exception> suppressedExceptions;

	/** Flag that indicates whether we're currently within destroySingletons. */
	private boolean singletonsCurrentlyInDestruction = false;

	/** Disposable bean instances: bean name to disposable instance. */
	private final Map<String, Object> disposableBeans = new LinkedHashMap<>();

	/** Map between containing bean names: bean name to Set of bean names that the bean contains. */
	private final Map<String, Set<String>> containedBeanMap = new ConcurrentHashMap<>(16);

	/** Map between dependent bean names: bean name to Set of dependent bean names. */
	private final Map<String, Set<String>> dependentBeanMap = new ConcurrentHashMap<>(64);

	/** Map between depending bean names: bean name to Set of bean names for the bean's dependencies. */
	private final Map<String, Set<String>> dependenciesForBeanMap = new ConcurrentHashMap<>(64);

//继承自SimpleAliasRegistry
	/** Map from alias to canonical name. */
	private final Map<String, String> aliasMap = new ConcurrentHashMap<>(16);

构造方法的调用

//SpringBoot的启动方法run方法中，创建AnnotationConfigServletWebServerApplicationContext过程中初始化，实际由父类GenericApplicationContext类创建
//递归调用父类的构造函数
	public DefaultListableBeanFactory() {
		super();
	}
//手动添加自动装配过程中排除实现了特定接口的类
public AbstractAutowireCapableBeanFactory() {
		super();
		ignoreDependencyInterface(BeanNameAware.class);
		ignoreDependencyInterface(BeanFactoryAware.class);
		ignoreDependencyInterface(BeanClassLoaderAware.class);
	}

单例注册方法

//由实例自己调用注册自己
	public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
		super.registerSingleton(beanName, singletonObject);
//用来判断当前启动的时机
		if (hasBeanCreationStarted()) {
             // 看似都是往手动添加的单例集合末尾添加元素，但操作不同，给出的理由很有意思：固定启动时的集合避免修改
			// Cannot modify startup-time collection elements anymore (for stable iteration)
			synchronized (this.beanDefinitionMap) {
				if (!this.beanDefinitionMap.containsKey(beanName)) {
					Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames.size() + 1);
					updatedSingletons.addAll(this.manualSingletonNames);
					updatedSingletons.add(beanName);
					this.manualSingletonNames = updatedSingletons;
				}
			}
		}
		else {
			// Still in startup registration phase
			if (!this.beanDefinitionMap.containsKey(beanName)) {
				this.manualSingletonNames.add(beanName);
			}
		}

		clearByTypeCache();
	}

//父类实现，主要是检查，锁定并调用添加方法
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
		Assert.notNull(beanName, "Bean name must not be null");
		Assert.notNull(singletonObject, "Singleton object must not be null");
		synchronized (this.singletonObjects) {
			Object oldObject = this.singletonObjects.get(beanName);
			if (oldObject != null) {
				throw new IllegalStateException("Could not register object [" + singletonObject +
						"] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
			}
			addSingleton(beanName, singletonObject);
		}
	}
//核心方法，可以看到注入一个完成单例的时候需要基于双重检查锁，同时消除2级缓存和三级缓存的信息
protected void addSingleton(String beanName, Object singletonObject) {
		synchronized (this.singletonObjects) {
			this.singletonObjects.put(beanName, singletonObject);
			this.singletonFactories.remove(beanName);
			this.earlySingletonObjects.remove(beanName);
			this.registeredSingletons.add(beanName);
		}
	}

beanDefinition注册

	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");
//AbstractBeanDefinition的实现需要做早期校验
		if (beanDefinition instanceof AbstractBeanDefinition) {
			try {
				((AbstractBeanDefinition) beanDefinition).validate();
			}
			catch (BeanDefinitionValidationException ex) {
				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
						"Validation of bean definition failed", ex);
			}
		}
//如果map中已经存在同名的情况下的处理逻辑
		BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
		if (existingDefinition != null) {
			if (!isAllowBeanDefinitionOverriding()) {
				throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
			}
			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 + "]");
				}
			}
//这里还要判断一次是否equal
			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 + "]");
				}
			}
			this.beanDefinitionMap.put(beanName, beanDefinition);
		}
		else {
//启动周期判断
			if (hasBeanCreationStarted()) {
//和之前方法一样，选择新构建一个list记录updatedDefinitions
				// Cannot modify startup-time collection elements anymore (for stable iteration)
				synchronized (this.beanDefinitionMap) {
					this.beanDefinitionMap.put(beanName, beanDefinition);
					List<String> updatedDefinitions = new ArrayList<>(this.beanDefinitionNames.size() + 1);
					updatedDefinitions.addAll(this.beanDefinitionNames);
					updatedDefinitions.add(beanName);
					this.beanDefinitionNames = updatedDefinitions;
					if (this.manualSingletonNames.contains(beanName)) {
						Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
						updatedSingletons.remove(beanName);
						this.manualSingletonNames = updatedSingletons;
					}
				}
			}
			else {
				// Still in startup registration phase
				this.beanDefinitionMap.put(beanName, beanDefinition);
				this.beanDefinitionNames.add(beanName);
				this.manualSingletonNames.remove(beanName);
			}
			this.frozenBeanDefinitionNames = null;
		}

		if (existingDefinition != null || containsSingleton(beanName)) {
			resetBeanDefinition(beanName);
		}
	}

获取单例（父类方法）

//可以一窥三级缓存处理的逻辑
protected Object getSingleton(String beanName, boolean allowEarlyReference) {
		Object singletonObject = this.singletonObjects.get(beanName);
		if (singletonObject == null && isSingletonCurrentlyInCreation(beanName)) {
			synchronized (this.singletonObjects) {
//二级缓存
				singletonObject = this.earlySingletonObjects.get(beanName);
				if (singletonObject == null && allowEarlyReference) {
//三级缓存
					ObjectFactory<?> singletonFactory = this.singletonFactories.get(beanName);
					if (singletonFactory != null) {
						singletonObject = singletonFactory.getObject();
						this.earlySingletonObjects.put(beanName, singletonObject);
						this.singletonFactories.remove(beanName);
					}
				}
			}
		}
		return singletonObject;
	}

预初始化非懒加载bean

//流程上再context refresh主流程的第11步的最后一个操作，前置操作包括初始化类型转换器，初始化内嵌值解析器，提前初始化加载期织入bean，置空临时类加载器并冻结配置项
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.
		List<String> beanNames = new ArrayList<>(this.beanDefinitionNames);

		// Trigger initialization of all non-lazy singleton beans...
		for (String beanName : beanNames) {
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
//获取RootBeanDefinition，判断是否需要在当前流程中初始化
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
//如果是工厂bean还需要判断是否是饿汉式，最终在getBean#doGetbean方法中完成初始化
				if (isFactoryBean(beanName)) {
					Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
					if (bean instanceof FactoryBean) {
						final FactoryBean<?> factory = (FactoryBean<?>) bean;
						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) {
							getBean(beanName);
						}
					}
				}
				else {
					getBean(beanName);
				}
			}
		}

		// Trigger post-initialization callback for all applicable beans...
		for (String beanName : beanNames) {
//上述的getSingleton方法，涉及三级缓存
			Object singletonInstance = getSingleton(beanName);
//对符合要求的单例进行后置处理
			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();
				}
			}
		}
	}