Spring IOC学习

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Spring被广泛应用于Java应用程序中，IOC容器以及AOP是其两大核心模块。首先，我们先学习一下IOC容器的设计思想，它提供了强大的控制反转以及依赖注入功能，让bean的构造和管理从应用中脱离出来，由Spring来管理bean的生命周期。

Bean的解析

在应用程序中，一般我们使用如下方式来从Spring的IOC容器中获取bean：

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ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
        Hello hello = context.getBean("hello", Hello.class);

通过初始化ApplicationContext应用上下文，Spring通过读取配置文件来解析xml中的bean。下面我们首先看一下application的类继承关系，
img
img
Spring提供了很多接口来便于扩展，以ClassPathXmlApplicationContext为例，简单介绍一下bean的解析过程，入口如下：

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public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException {
        super(parent);
        //解析配置文件，存放配置文件地址
        this.setConfigLocations(configLocations);
        if(refresh) {
            this.refresh();
        }
    }

上面代码中最重要的是refresh方法，它是整个应用上下文初始化的开始：

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public void refresh() throws BeansException, IllegalStateException {
	//加锁，防止多线程同时加载
		synchronized (this.startupShutdownMonitor) {
			// 设置加载标志，初始加载时间
			prepareRefresh();
			// bean的解析过程，beanName-> beanDefinition
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
			// beanFactory的准备工作，设置加载器以及BeanPostProcessor
			prepareBeanFactory(beanFactory);
			try {
				//留给子类的扩展点，添加一些BeanFactoryPostProcessor，在bean实例化之前进行某些操作
				postProcessBeanFactory(beanFactory);
				// 调用BeanFactoryPostProcessor实现类的postProcessBeanFactory(factory)方法
				invokeBeanFactoryPostProcessors(beanFactory);
				// 添加BeanPostProcessor的实现类，postProcessBeforeInitialization 和 postProcessAfterInitialization分别在bean初始化前后调用
				// 初始化前指bean已经实例化了，反射调用了构造函数，setter以及注解注入的属性
				registerBeanPostProcessors(beanFactory);	
				// 国际化相关
				initMessageSource();
				// Initialize event multicaster for this context.
				initApplicationEventMulticaster();
				// Initialize other special beans in specific context subclasses.
				onRefresh();
				// Check for listener beans and register them.
				registerListeners();
				// 初始化所有单例的、非abstarct、非懒加载的bean，beanDefinition->bean实例
				finishBeanFactoryInitialization(beanFactory);
				// 广播事件，applicationContext初始化完成
				finishRefresh();
			}
			catch (BeansException ex) {
				if (logger.isWarnEnabled()) {
					logger.warn("Exception encountered during context initialization - " +
							"cancelling refresh attempt: " + ex);
				}
				// Destroy already created singletons to avoid dangling resources.
				destroyBeans();
				// Reset 'active' flag.
				cancelRefresh(ex);
				// Propagate exception to caller.
				throw ex;
			}
			finally {
				// Reset common introspection caches in Spring's core, since we
				// might not ever need metadata for singleton beans anymore...
				resetCommonCaches();
			}
		}
	}

obtainFreshBeanFactory方法代码如下：

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protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
		refreshBeanFactory();
		ConfigurableListableBeanFactory beanFactory = getBeanFactory();
		if (logger.isDebugEnabled()) {
			logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
		}
		return beanFactory;
	}
protected final void refreshBeanFactory() throws BeansException {
	// 销毁已经创建的beanFactory
		if (hasBeanFactory()) {
			destroyBeans();
			closeBeanFactory();
		}
		try {
			// 创建beanFactory
			DefaultListableBeanFactory beanFactory = createBeanFactory();
			beanFactory.setSerializationId(getId());
			//是否允许bean覆盖（同一applicationConetxt定义相同beanName的bean）、是否允许循环依赖
			customizeBeanFactory(beanFactory);
			// 解析bean的配置文件
			loadBeanDefinitions(beanFactory);
			//设置beanFactory，这里AbstractRefreshableApplicationContext持有了beanFactory引用
			// 虽然applicationContext继承了beanFactory但是实际上是一种组合模式，使用beanFactory来管理bean
			synchronized (this.beanFactoryMonitor) {
				this.beanFactory = beanFactory;
			}
		}
		catch (IOException ex) {
			throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);
		}
	}

loadBeanDefinitions解析过程链路较长，下面给出一些主要的方法调用步骤，简单讲解下核心的过程：
AbstractXmlApplicationContext的loadBeanDefinitions方法->AbstractBeanDefinitionReader的loadBeanDefinitions方法->XmlBeanDefinitionReader的doLoadBeanDefinitions方法和registerBeanDefinitions方法->DefaultBeanDefinitionDocumentReader的doRegisterBeanDefinitions方法，

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protected void doRegisterBeanDefinitions(Element root) {
	//  负责解析bean的核心类
        BeanDefinitionParserDelegate parent = this.delegate;
        this.delegate = this.createDelegate(this.getReaderContext(), root, parent);
        //根结点的profile属性，如dev、prod等环境
        if(this.delegate.isDefaultNamespace(root)) {
            String profileSpec = root.getAttribute("profile");
            if(StringUtils.hasText(profileSpec)) {
                String[] specifiedProfiles = StringUtils.tokenizeToStringArray(profileSpec, ",; ");
                if(!this.getReaderContext().getEnvironment().acceptsProfiles(specifiedProfiles)) {
                    if(this.logger.isInfoEnabled()) {
                        this.logger.info("Skipped XML bean definition file due to specified profiles [" + profileSpec + "] not matching: " + this.getReaderContext().getResource());
                    }
                    return;
                }
            }
        }
        this.preProcessXml(root);
        // 解析bean
        this.parseBeanDefinitions(root, this.delegate);
        this.postProcessXml(root);
        this.delegate = parent;
    }
   protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
        if(delegate.isDefaultNamespace(root)) {
            NodeList nl = root.getChildNodes();
            for(int i = 0; i < nl.getLength(); ++i) {
                Node node = nl.item(i);
                if(node instanceof Element) {
                    Element ele = (Element)node;
                    if(delegate.isDefaultNamespace(ele)) {
                    	//解析default标签，处于http://www.springframework.org/schema/beans下的
                        this.parseDefaultElement(ele, delegate);
                    } else {
                        delegate.parseCustomElement(ele);
                    }
                }
            }
        } else {
            delegate.parseCustomElement(root);
        }
    }
    //解析 import、alias、bean、beans等标签
    private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
        if(delegate.nodeNameEquals(ele, "import")) {
            this.importBeanDefinitionResource(ele);
        } else if(delegate.nodeNameEquals(ele, "alias")) {
            this.processAliasRegistration(ele);
        } else if(delegate.nodeNameEquals(ele, "bean")) {
            this.processBeanDefinition(ele, delegate);
        } else if(delegate.nodeNameEquals(ele, "beans")) {
        	嵌套beans需要递归解析
            this.doRegisterBeanDefinitions(ele);
        }
    }

下面主要分析bean标签的解析，beans的解析嵌套，需要多次递归调用，最终也会到bean标签的解析

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protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
	// 解析bean的核心方法
      BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
      if(bdHolder != null) {
          bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
          try {
          	// 注册bean，beanName->beanDefinition
              BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, this.getReaderContext().getRegistry());
          } catch (BeanDefinitionStoreException var5) {
              this.getReaderContext().error("Failed to register bean definition with name \'" + bdHolder.getBeanName() + "\'", ele, var5);
          }
          this.getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
      }
  }
  public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
  	// 获取id和name标签
      String id = ele.getAttribute("id");
      String nameAttr = ele.getAttribute("name");
      ArrayList aliases = new ArrayList();
      //别名
      if(StringUtils.hasLength(nameAttr)) {
          String[] beanName = StringUtils.tokenizeToStringArray(nameAttr, ",; ");
          aliases.addAll(Arrays.asList(beanName));
      }
      String beanName1 = id;
      if(!StringUtils.hasText(id) && !aliases.isEmpty()) {
          beanName1 = (String)aliases.remove(0);
          if(this.logger.isDebugEnabled()) {
              this.logger.debug("No XML \'id\' specified - using \'" + beanName1 + "\' as bean name and " + aliases + " as aliases");
          }
      }
      // 检查是否存在同名的beanName
      if(containingBean == null) {
          this.checkNameUniqueness(beanName1, aliases, ele);
      }
      // 解析bean的属性
      AbstractBeanDefinition beanDefinition = this.parseBeanDefinitionElement(ele, beanName1, containingBean);
      if(beanDefinition != null) {
      	//没有设置id和name，自动生成beanName，按是否内部类等生成
          if(!StringUtils.hasText(beanName1)) {
              try {
                  if(containingBean != null) {
                      beanName1 = BeanDefinitionReaderUtils.generateBeanName(beanDefinition, this.readerContext.getRegistry(), true);
                  } else {
                      beanName1 = this.readerContext.generateBeanName(beanDefinition);
                      String aliasesArray = beanDefinition.getBeanClassName();
                      if(aliasesArray != null && beanName1.startsWith(aliasesArray) && beanName1.length() > aliasesArray.length() && !this.readerContext.getRegistry().isBeanNameInUse(aliasesArray)) {
                          aliases.add(aliasesArray);
                      }
                  }
                  if(this.logger.isDebugEnabled()) {
                      this.logger.debug("Neither XML \'id\' nor \'name\' specified - using generated bean name [" + beanName1 + "]");
                  }
              } catch (Exception var9) {
                  this.error(var9.getMessage(), ele);
                  return null;
              }
          }
          String[] aliasesArray1 = StringUtils.toStringArray(aliases);
          return new BeanDefinitionHolder(beanDefinition, beanName1, aliasesArray1);
      } else {
          return null;
      }
  }
  public AbstractBeanDefinition parseBeanDefinitionElement(Element ele, String beanName, BeanDefinition containingBean) {
      this.parseState.push(new BeanEntry(beanName));
      String className = null;
      if(ele.hasAttribute("class")) {
          className = ele.getAttribute("class").trim();
      }
      try {
          String ex = null;
          if(ele.hasAttribute("parent")) {
              ex = ele.getAttribute("parent");
          }
          //设置beanDefinition的信息
          AbstractBeanDefinition bd = this.createBeanDefinition(className, ex);
          //设置bean的scope、init、destory、abstract等信息
          this.parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
          bd.setDescription(DomUtils.getChildElementValueByTagName(ele, "description"));
          // 解析meta标签
          this.parseMetaElements(ele, bd);
          // 解析look-up标签
          this.parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
          // 解析replace标签
          this.parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
          // 解析construct-arg标签
          this.parseConstructorArgElements(ele, bd);
          // 解析property标签
          this.parsePropertyElements(ele, bd);
          // 解析qualifier标签
          this.parseQualifierElements(ele, bd);
          bd.setResource(this.readerContext.getResource());
          bd.setSource(this.extractSource(ele));
          AbstractBeanDefinition var7 = bd;
          return var7;
      } catch (ClassNotFoundException var13) {
          this.error("Bean class [" + className + "] not found", ele, var13);
      } catch (NoClassDefFoundError var14) {
          this.error("Class that bean class [" + className + "] depends on not found", ele, var14);
      } catch (Throwable var15) {
          this.error("Unexpected failure during bean definition parsing", ele, var15);
      } finally {
          this.parseState.pop();
      }
      return null;
  }

完成bean的解析后，得到了beanDefinition对象，这里面包含了bean的定义和属性，下面继续看bean的注册过程：BeanDefinitionReaderUtils.registerBeanDefinition

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public static void registerBeanDefinition(
			BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
			throws BeanDefinitionStoreException {
		// Register bean definition under primary name.
		String beanName = definitionHolder.getBeanName();
		// 注册bean
		registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
		// Register aliases for bean name, if any.
		String[] aliases = definitionHolder.getAliases();
		if (aliases != null) {
			for (String alias : aliases) {
				// bean别名的注册
				registry.registerAlias(beanName, alias);
			}
		}
	}
	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");
		if (beanDefinition instanceof AbstractBeanDefinition) {
			try {
				((AbstractBeanDefinition) beanDefinition).validate();
			}
			catch (BeanDefinitionValidationException ex) {
				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
						"Validation of bean definition failed", ex);
			}
		}
		BeanDefinition oldBeanDefinition;
		//是否有同名的bean
		oldBeanDefinition = this.beanDefinitionMap.get(beanName);
		if (oldBeanDefinition != null) {
			// 是否允许bean覆盖
			if (!isAllowBeanDefinitionOverriding()) {
				throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
						"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
						"': There is already [" + oldBeanDefinition + "] bound.");
			}
			else if (oldBeanDefinition.getRole() < beanDefinition.getRole()) {
				// e.g. was ROLE_APPLICATION, now overriding with ROLE_SUPPORT or ROLE_INFRASTRUCTURE
				if (this.logger.isWarnEnabled()) {
					this.logger.warn("Overriding user-defined bean definition for bean '" + beanName +
							"' with a framework-generated bean definition: replacing [" +
							oldBeanDefinition + "] with [" + beanDefinition + "]");
				}
			}
			else if (!beanDefinition.equals(oldBeanDefinition)) {
				if (this.logger.isInfoEnabled()) {
					this.logger.info("Overriding bean definition for bean '" + beanName +
							"' with a different definition: replacing [" + oldBeanDefinition +
							"] with [" + beanDefinition + "]");
				}
			}
			else {
				if (this.logger.isDebugEnabled()) {
					this.logger.debug("Overriding bean definition for bean '" + beanName +
							"' with an equivalent definition: replacing [" + oldBeanDefinition +
							"] with [" + beanDefinition + "]");
				}
			}
			// 覆盖同名的bean
			this.beanDefinitionMap.put(beanName, beanDefinition);
		}
		else {
			if (hasBeanCreationStarted()) {
				// Cannot modify startup-time collection elements anymore (for stable iteration)
				synchronized (this.beanDefinitionMap) {
					// 添加bean
					this.beanDefinitionMap.put(beanName, beanDefinition);
					List<String> updatedDefinitions = new ArrayList<String>(this.beanDefinitionNames.size() + 1);
					updatedDefinitions.addAll(this.beanDefinitionNames);
					updatedDefinitions.add(beanName);
					this.beanDefinitionNames = updatedDefinitions;
					// 删除手动添加的bean
					if (this.manualSingletonNames.contains(beanName)) {
						Set<String> updatedSingletons = new LinkedHashSet<String>(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 (oldBeanDefinition != null || containsSingleton(beanName)) {
			resetBeanDefinition(beanName);
		}
	}
	public void registerAlias(String name, String alias) {
        Assert.hasText(name, "\'name\' must not be empty");
        Assert.hasText(alias, "\'alias\' must not be empty");
        if(alias.equals(name)) {
            this.aliasMap.remove(alias);
        } else {
            String registeredName = (String)this.aliasMap.get(alias);
            if(registeredName != null) {
                if(registeredName.equals(name)) {
                    return;
                }
                //alias->beanName已经存在了，看是否允许bean重名
                if(!this.allowAliasOverriding()) {
                    throw new IllegalStateException("Cannot register alias \'" + alias + "\' for name \'" + name + "\': It is already registered for name \'" + registeredName + "\'.");
                }
            }
            this.checkForAliasCircle(name, alias);
            //用map保存别名和beanName的关系
            this.aliasMap.put(alias, name);
        }
    }

到这里，bean的解析已经完成了，这一过程主要是把构造bean->beanDefinition的对应关系，涉及到的主要类和方法如下：
img

Bean的初始化

完成bean的解析后，接下来将对bean进行初始化，继续跟进refresh方法，首先看一下prepareBeanFactory(factory）方法，该方法主要注册几个BeanPostProcessor：

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protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
		// 设置类加载器
		beanFactory.setBeanClassLoader(getClassLoader());
		beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
		beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
		// 添加ApplicationContextAwareProcessor这个BeanPostProcessor
		beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
		// bean依赖以下特殊的bean会忽略掉
		beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
		beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
		beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
		beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
		beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
		// 若bean依赖以下bean，则进行注入，applicationContext继承这些类
		beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
		beanFactory.registerResolvableDependency(ResourceLoader.class, this);
		beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
		beanFactory.registerResolvableDependency(ApplicationContext.class, this);
		// Register early post-processor for detecting inner beans as ApplicationListeners.
		beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
		// Detect a LoadTimeWeaver and prepare for weaving, if found.
		if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
			beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
			// Set a temporary ClassLoader for type matching.
			beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
		}
		// 注册几个特殊的bean，已系统和环境相关
		if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
		}
		if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
			beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
		}
	}

接下来，我们来看下最重要的方法finishBeanFactoryInitialization,它会初始化所有单例、非抽象、非懒加载的bean，

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protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
		// 初始化名字为 conversionService 的 Bean，这个类和类型转换有关
		if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
				beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
			beanFactory.setConversionService(
					beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
		}
		// Register a default embedded value resolver if no bean post-processor
		// (such as a PropertyPlaceholderConfigurer bean) registered any before:
		// at this point, primarily for resolution in annotation attribute values.
		if (!beanFactory.hasEmbeddedValueResolver()) {
			beanFactory.addEmbeddedValueResolver(new StringValueResolver() {
				@Override
				public String resolveStringValue(String strVal) {
					return getEnvironment().resolvePlaceholders(strVal);
				}
			});
		}
		// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
		String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
		for (String weaverAwareName : weaverAwareNames) {
			getBean(weaverAwareName);
		}
		// Stop using the temporary ClassLoader for type matching.
		beanFactory.setTempClassLoader(null);
		// 冻结bean的其他操作，如解析、注册，为bean初始化做准备
		beanFactory.freezeConfiguration();
		// 开始初始化单例bean
		beanFactory.preInstantiateSingletons();
	}
	public void preInstantiateSingletons() throws BeansException {
		if (this.logger.isDebugEnabled()) {
			this.logger.debug("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<String>(this.beanDefinitionNames);
		// Trigger initialization of all non-lazy singleton beans...
		for (String beanName : beanNames) {
			// 合并父类bean中的配置
			RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
			// bean是单例、不是抽象、不是懒加载的则进行初始化
			if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
				if (isFactoryBean(beanName)) {
					// 是FactoryBean则beanName加&符号后 再getBean初始化
					final FactoryBean<?> factory = (FactoryBean<?>) getBean(FACTORY_BEAN_PREFIX + beanName);
					boolean isEagerInit;
					if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
						isEagerInit = AccessController.doPrivileged(new PrivilegedAction<Boolean>() {
							@Override
							public Boolean run() {
								return ((SmartFactoryBean<?>) factory).isEagerInit();
							}
						}, getAccessControlContext());
					}
					else {
						isEagerInit = (factory instanceof SmartFactoryBean &&
								((SmartFactoryBean<?>) factory).isEagerInit());
					}
					if (isEagerInit) {
						getBean(beanName);
					}
				}
				else {
					// 普调bean初始化
					getBean(beanName);
				}
			}
		}
		//  bean 实现了 SmartInitializingSingleton 接口，那么回调afterSingletonsInstantiated方法
		for (String beanName : beanNames) {
			Object singletonInstance = getSingleton(beanName);
			if (singletonInstance instanceof SmartInitializingSingleton) {
				final SmartInitializingSingleton smartSingleton = (SmartInitializingSingleton) singletonInstance;
				if (System.getSecurityManager() != null) {
					AccessController.doPrivileged(new PrivilegedAction<Object>() {
						@Override
						public Object run() {
							smartSingleton.afterSingletonsInstantiated();
							return null;
						}
					}, getAccessControlContext());
				}
				else {
					smartSingleton.afterSingletonsInstantiated();
				}
			}
		}
	}

接下来分析下getBean方法的过程，该方法也是我们获取bean的主要方式：

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public Object getBean(String name) throws BeansException {
		return doGetBean(name, null, null, false);
	}
protected <T> T doGetBean(
			final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
			throws BeansException {
		// beanName转换，先讲bean类型为beanFactory的去除&前缀，然后再根据别名->beanName映射将别名转化为beanName
		final String beanName = transformedBeanName(name);
		Object bean;
		// 是否已经创建了bean
		Object sharedInstance = getSingleton(beanName);
		// 注意args不为空是，即使获取到了bean也要重新初始化bean
		if (sharedInstance != null && args == null) {
			if (logger.isDebugEnabled()) {
				if (isSingletonCurrentlyInCreation(beanName)) {
					logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
							"' that is not fully initialized yet - a consequence of a circular reference");
				}
				else {
					logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
				}
			}
			//获取普通bean，若bean是FactoryBean则获取它构造的bean	
			bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
		}
		else {
			// Fail if we're already creating this bean instance:
			// We're assumably within a circular reference.
			if (isPrototypeCurrentlyInCreation(beanName)) {
				throw new BeanCurrentlyInCreationException(beanName);
			}
			// 当前beanFactory没有该bean定义则从父beanFactory去获取bean
			BeanFactory parentBeanFactory = getParentBeanFactory();
			if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
				// Not found -> check parent.
				String nameToLookup = originalBeanName(name);
				if (args != null) {
					// Delegation to parent with explicit args.
					return (T) parentBeanFactory.getBean(nameToLookup, args);
				}
				else {
					// No args -> delegate to standard getBean method.
					return parentBeanFactory.getBean(nameToLookup, requiredType);
				}
			}
			if (!typeCheckOnly) {
				markBeanAsCreated(beanName);
			}
			try {
				final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
				checkMergedBeanDefinition(mbd, beanName, args);
				// 先初始化被依赖的bean，depend-on标签
				String[] dependsOn = mbd.getDependsOn();
				if (dependsOn != null) {
					for (String dep : dependsOn) {
						if (isDependent(beanName, dep)) {
							throw new BeanCreationException(mbd.getResourceDescription(), beanName,
									"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
						}
						//注册依赖关系
						registerDependentBean(dep, beanName);
						getBean(dep);
					}
				}
				// 创建单例bean
				if (mbd.isSingleton()) {
					sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
						@Override
						public Object getObject() throws BeansException {
							try {
								return createBean(beanName, mbd, args);
							}
							catch (BeansException ex) {
								// Explicitly remove instance from singleton cache: It might have been put there
								// eagerly by the creation process, to allow for circular reference resolution.
								// Also remove any beans that received a temporary reference to the bean.
								destroySingleton(beanName);
								throw ex;
							}
						}
					});
					bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
				}
				//创建prototype bean
				else if (mbd.isPrototype()) {
					// It's a prototype -> create a new instance.
					Object prototypeInstance = null;
					try {
						beforePrototypeCreation(beanName);
						prototypeInstance = createBean(beanName, mbd, args);
					}
					finally {
						afterPrototypeCreation(beanName);
					}
					bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
				}
				else {
					String scopeName = mbd.getScope();
					final Scope scope = this.scopes.get(scopeName);
					if (scope == null) {
						throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
					}
					try {
						Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
							@Override
							public Object getObject() throws BeansException {
								beforePrototypeCreation(beanName);
								try {
									return createBean(beanName, mbd, args);
								}
								finally {
									afterPrototypeCreation(beanName);
								}
							}
						});
						bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
					}
					catch (IllegalStateException ex) {
						throw new BeanCreationException(beanName,
								"Scope '" + scopeName + "' is not active for the current thread; consider " +
								"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
								ex);
					}
				}
			}
			catch (BeansException ex) {
				cleanupAfterBeanCreationFailure(beanName);
				throw ex;
			}
		}
		// Check if required type matches the type of the actual bean instance.
		if (requiredType != null && bean != null && !requiredType.isAssignableFrom(bean.getClass())) {
			try {
				return getTypeConverter().convertIfNecessary(bean, requiredType);
			}
			catch (TypeMismatchException ex) {
				if (logger.isDebugEnabled()) {
					logger.debug("Failed to convert bean '" + name + "' to required type '" +
							ClassUtils.getQualifiedName(requiredType) + "'", ex);
				}
				throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
			}
		}
		return (T) bean;
	}

下面我们以单例bean为例了解bean的创建过程：

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public Object getSingleton(String beanName, ObjectFactory<?> singletonFactory) {
		Assert.notNull(beanName, "'beanName' must not be null");
		synchronized (this.singletonObjects) {
			// 先从singletonObjects中获取bean
			Object singletonObject = this.singletonObjects.get(beanName);
			if (singletonObject == null) {
				if (this.singletonsCurrentlyInDestruction) {
					throw new BeanCreationNotAllowedException(beanName,
							"Singleton bean creation not allowed while singletons of this factory are in destruction " +
							"(Do not request a bean from a BeanFactory in a destroy method implementation!)");
				}
				if (logger.isDebugEnabled()) {
					logger.debug("Creating shared instance of singleton bean '" + beanName + "'");
				}
				beforeSingletonCreation(beanName);
				boolean newSingleton = false;
				boolean recordSuppressedExceptions = (this.suppressedExceptions == null);
				if (recordSuppressedExceptions) {
					this.suppressedExceptions = new LinkedHashSet<Exception>();
				}
				try {
					// 调用ObjectFactory的getObject方法创建bean，即createBean方法
					singletonObject = singletonFactory.getObject();
					newSingleton = true;
				}
				catch (IllegalStateException ex) {
					// Has the singleton object implicitly appeared in the meantime ->
					// if yes, proceed with it since the exception indicates that state.
					singletonObject = this.singletonObjects.get(beanName);
					if (singletonObject == null) {
						throw ex;
					}
				}
				catch (BeanCreationException ex) {
					if (recordSuppressedExceptions) {
						for (Exception suppressedException : this.suppressedExceptions) {
							ex.addRelatedCause(suppressedException);
						}
					}
					throw ex;
				}
				finally {
					if (recordSuppressedExceptions) {
						this.suppressedExceptions = null;
					}
					afterSingletonCreation(beanName);
				}
				if (newSingleton) {
					//创建完成后，放入singletonObject这个map中表示bean初始化完成
					addSingleton(beanName, singletonObject);
				}
			}
			return (singletonObject != NULL_OBJECT ? singletonObject : null);
		}
	}

下面，继续看createBean如何创建bean：

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protected Object createBean(String beanName, RootBeanDefinition mbd, Object[] args) throws BeanCreationException {
		if (logger.isDebugEnabled()) {
			logger.debug("Creating instance of bean '" + beanName + "'");
		}
		RootBeanDefinition mbdToUse = mbd;
		// Make sure bean class is actually resolved at this point, and
		// clone the bean definition in case of a dynamically resolved Class
		// which cannot be stored in the shared merged bean definition.
		Class<?> resolvedClass = resolveBeanClass(mbd, beanName);
		if (resolvedClass != null && !mbd.hasBeanClass() && mbd.getBeanClassName() != null) {
			mbdToUse = new RootBeanDefinition(mbd);
			mbdToUse.setBeanClass(resolvedClass);
		}
		// Prepare method overrides.
		try {
			mbdToUse.prepareMethodOverrides();
		}
		catch (BeanDefinitionValidationException ex) {
			throw new BeanDefinitionStoreException(mbdToUse.getResourceDescription(),
					beanName, "Validation of method overrides failed", ex);
		}
		try {
			// 可以使用InstantiationAwareBeanPostProcessor来直接创建bean，spring aop创建bean的代理时会用到，后面看懂后在详细分析
			Object bean = resolveBeforeInstantiation(beanName, mbdToUse);
			if (bean != null) {
				return bean;
			}
		}
		catch (Throwable ex) {
			throw new BeanCreationException(mbdToUse.getResourceDescription(), beanName,
					"BeanPostProcessor before instantiation of bean failed", ex);
		}
		//正常创建bean流程
		Object beanInstance = doCreateBean(beanName, mbdToUse, args);
		if (logger.isDebugEnabled()) {
			logger.debug("Finished creating instance of bean '" + beanName + "'");
		}
		return beanInstance;
	}
	protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
			throws BeanCreationException {
		// Instantiate the bean.
		BeanWrapper instanceWrapper = null;
		if (mbd.isSingleton()) {
			instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
		}
		if (instanceWrapper == null) {
			//反射创建bean并用instanceWrapper进行封装
			instanceWrapper = createBeanInstance(beanName, mbd, args);
		}
		final Object bean = (instanceWrapper != null ? instanceWrapper.getWrappedInstance() : null);
		Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
		mbd.resolvedTargetType = beanType;
		// Allow post-processors to modify the merged bean definition.
		synchronized (mbd.postProcessingLock) {
			if (!mbd.postProcessed) {
				try {
					applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
				}
				catch (Throwable ex) {
					throw new BeanCreationException(mbd.getResourceDescription(), beanName,
							"Post-processing of merged bean definition failed", ex);
				}
				mbd.postProcessed = true;
			}
		}
		// 解决循环依赖问题，单例允许循环依赖的话提前将beanFactroy放入singletonFactories这个map中，则其他bean依赖该bean可以通过singletonFactories来获取当前bean，其实singletonFactories和earlySingletonObjects都是bean实例化中的中间过程，为了解决循环依赖问题，最终创建完成后bean放入singletonObjects中
		boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
				isSingletonCurrentlyInCreation(beanName));
		if (earlySingletonExposure) {
			if (logger.isDebugEnabled()) {
				logger.debug("Eagerly caching bean '" + beanName +
						"' to allow for resolving potential circular references");
			}
			addSingletonFactory(beanName, new ObjectFactory<Object>() {
				@Override
				public Object getObject() throws BeansException {
					return getEarlyBeanReference(beanName, mbd, bean);
				}
			});
		}
		// Initialize the bean instance.
		Object exposedObject = bean;
		try {
			// bean的属性注入过程
			populateBean(beanName, mbd, instanceWrapper);
			if (exposedObject != null) {
				// bean初始化方法调用，InitializingBean、BeanPostProcessor 、init-method
				exposedObject = initializeBean(beanName, exposedObject, mbd);
			}
		}
		catch (Throwable ex) {
			if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
				throw (BeanCreationException) ex;
			}
			else {
				throw new BeanCreationException(
						mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
			}
		}
		if (earlySingletonExposure) {
			Object earlySingletonReference = getSingleton(beanName, false);
			if (earlySingletonReference != null) {
				if (exposedObject == bean) {
					exposedObject = earlySingletonReference;
				}
				else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
					String[] dependentBeans = getDependentBeans(beanName);
					Set<String> actualDependentBeans = new LinkedHashSet<String>(dependentBeans.length);
					for (String dependentBean : dependentBeans) {
						if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
							actualDependentBeans.add(dependentBean);
						}
					}
					if (!actualDependentBeans.isEmpty()) {
						throw new BeanCurrentlyInCreationException(beanName,
								"Bean with name '" + beanName + "' has been injected into other beans [" +
								StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
								"] in its raw version as part of a circular reference, but has eventually been " +
								"wrapped. This means that said other beans do not use the final version of the " +
								"bean. This is often the result of over-eager type matching - consider using " +
								"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
					}
				}
			}
		}
		// Register bean as disposable.
		try {
			registerDisposableBeanIfNecessary(beanName, bean, mbd);
		}
		catch (BeanDefinitionValidationException ex) {
			throw new BeanCreationException(
					mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
		}
		return exposedObject;
	}
	//反射创建bean
protected BeanWrapper createBeanInstance(String beanName, RootBeanDefinition mbd, Object[] args) {
		// 加载类
		Class<?> beanClass = resolveBeanClass(mbd, beanName);
		if (beanClass != null && !Modifier.isPublic(beanClass.getModifiers()) && !mbd.isNonPublicAccessAllowed()) {
			throw new BeanCreationException(mbd.getResourceDescription(), beanName,
					"Bean class isn't public, and non-public access not allowed: " + beanClass.getName());
		}
		// 工厂类factortBean创建bean
		if (mbd.getFactoryMethodName() != null)  {
			return instantiateUsingFactoryMethod(beanName, mbd, args);
		}
		// Shortcut when re-creating the same bean...
		boolean resolved = false;
		boolean autowireNecessary = false;
		if (args == null) {
			synchronized (mbd.constructorArgumentLock) {
				if (mbd.resolvedConstructorOrFactoryMethod != null) {
					resolved = true;
					autowireNecessary = mbd.constructorArgumentsResolved;
				}
			}
		}
		if (resolved) {
			if (autowireNecessary) {
				// 构造函数注入
				return autowireConstructor(beanName, mbd, null, null);
			}
			else {
				//无参构造函数反射
				return instantiateBean(beanName, mbd);
			}
		}
		// Need to determine the constructor...
		Constructor<?>[] ctors = determineConstructorsFromBeanPostProcessors(beanClass, beanName);
		if (ctors != null ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_CONSTRUCTOR ||
				mbd.hasConstructorArgumentValues() || !ObjectUtils.isEmpty(args))  {
			return autowireConstructor(beanName, mbd, ctors, args);
		}
		// No special handling: simply use no-arg constructor.
		return instantiateBean(beanName, mbd);
	}

populateBean方法完成bean的属性填充，在这里有依赖bean的注入过程：

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protected void populateBean(String beanName, RootBeanDefinition mbd, BeanWrapper bw) {
		PropertyValues pvs = mbd.getPropertyValues();
		if (bw == null) {
			if (!pvs.isEmpty()) {
				throw new BeanCreationException(
						mbd.getResourceDescription(), beanName, "Cannot apply property values to null instance");
			}
			else {
				// Skip property population phase for null instance.
				return;
			}
		}
		// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
		// state of the bean before properties are set. This can be used, for example,
		// to support styles of field injection.
		boolean continueWithPropertyPopulation = true;
		if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
			for (BeanPostProcessor bp : getBeanPostProcessors()) {
				if (bp instanceof InstantiationAwareBeanPostProcessor) {
					InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
					if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
						continueWithPropertyPopulation = false;
						break;
					}
				}
			}
		}
		if (!continueWithPropertyPopulation) {
			return;
		}
		if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME ||
				mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
			MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
			// Add property values based on autowire by name if applicable.
			if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_NAME) {
				// 通过类型来依赖注入，这里的依赖注入是非基本类型的bean，并且属性没有显示定义
				autowireByName(beanName, mbd, bw, newPvs);
			}
			// Add property values based on autowire by type if applicable.
			if (mbd.getResolvedAutowireMode() == RootBeanDefinition.AUTOWIRE_BY_TYPE) {
				通过类型来依赖注入，这里的依赖注入是非基本类型的bean，并且属性没有显示定义
				autowireByType(beanName, mbd, bw, newPvs);
			}
			pvs = newPvs;
		}
		boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
		boolean needsDepCheck = (mbd.getDependencyCheck() != RootBeanDefinition.DEPENDENCY_CHECK_NONE);
		if (hasInstAwareBpps || needsDepCheck) {
			PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw, mbd.allowCaching);
			if (hasInstAwareBpps) {
				for (BeanPostProcessor bp : getBeanPostProcessors()) {
					if (bp instanceof InstantiationAwareBeanPostProcessor) {
						InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
						pvs = ibp.postProcessPropertyValues(pvs, filteredPds, bw.getWrappedInstance(), beanName);
						if (pvs == null) {
							return;
						}
					}
				}
			}
			if (needsDepCheck) {
				checkDependencies(beanName, mbd, filteredPds, pvs);
			}
		}
		// 属性的注入
		applyPropertyValues(beanName, mbd, bw, pvs);
	}
// 通过名称来自动注入
	protected void autowireByName(
			String beanName, AbstractBeanDefinition mbd, BeanWrapper bw, MutablePropertyValues pvs) {
		String[] propertyNames = unsatisfiedNonSimpleProperties(mbd, bw);
		for (String propertyName : propertyNames) {
			if (containsBean(propertyName)) {
				// getBean递归初始化依赖的bean
				Object bean = getBean(propertyName);
				pvs.add(propertyName, bean);
				// 依赖关系放入map中
				registerDependentBean(propertyName, beanName);
				if (logger.isDebugEnabled()) {
					logger.debug("Added autowiring by name from bean name '" + beanName +
							"' via property '" + propertyName + "' to bean named '" + propertyName + "'");
				}
			}
			else {
				if (logger.isTraceEnabled()) {
					logger.trace("Not autowiring property '" + propertyName + "' of bean '" + beanName +
							"' by name: no matching bean found");
				}
			}
		}
	}
	protected String[] unsatisfiedNonSimpleProperties(AbstractBeanDefinition mbd, BeanWrapper bw) {
		Set<String> result = new TreeSet<String>();
		PropertyValues pvs = mbd.getPropertyValues();
		PropertyDescriptor[] pds = bw.getPropertyDescriptors();
		for (PropertyDescriptor pd : pds) {
			// 没有显示定义的属性，并且是非基本类型的属性
			if (pd.getWriteMethod() != null && !isExcludedFromDependencyCheck(pd) && !pvs.contains(pd.getName()) &&
					!BeanUtils.isSimpleProperty(pd.getPropertyType())) {
				result.add(pd.getName());
			}
		}
		return StringUtils.toStringArray(result);
	}

最后，我们看applyPropertyValues这个方法中，它实现了bean各种属性的设置：

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protected void applyPropertyValues(String beanName, BeanDefinition mbd, BeanWrapper bw, PropertyValues pvs) {
		if (pvs == null || pvs.isEmpty()) {
			return;
		}
		MutablePropertyValues mpvs = null;
		List<PropertyValue> original;
		if (System.getSecurityManager() != null) {
			if (bw instanceof BeanWrapperImpl) {
				((BeanWrapperImpl) bw).setSecurityContext(getAccessControlContext());
			}
		}
		if (pvs instanceof MutablePropertyValues) {
			mpvs = (MutablePropertyValues) pvs;
			if (mpvs.isConverted()) {
				// Shortcut: use the pre-converted values as-is.
				try {
					bw.setPropertyValues(mpvs);
					return;
				}
				catch (BeansException ex) {
					throw new BeanCreationException(
							mbd.getResourceDescription(), beanName, "Error setting property values", ex);
				}
			}
			original = mpvs.getPropertyValueList();
		}
		else {
			original = Arrays.asList(pvs.getPropertyValues());
		}
		TypeConverter converter = getCustomTypeConverter();
		if (converter == null) {
			converter = bw;
		}
		// bean的属性类型的解析
		BeanDefinitionValueResolver valueResolver = new BeanDefinitionValueResolver(this, beanName, mbd, converter);
		// Create a deep copy, resolving any references for values.
		List<PropertyValue> deepCopy = new ArrayList<PropertyValue>(original.size());
		boolean resolveNecessary = false;
		for (PropertyValue pv : original) {
			if (pv.isConverted()) {
				deepCopy.add(pv);
			}
			else {
				String propertyName = pv.getName();
				Object originalValue = pv.getValue();
				// 解析bean属性的类型，如bean的引用（这会导致它所依赖bean的初始化），list、map、set等等类型
				Object resolvedValue = valueResolver.resolveValueIfNecessary(pv, originalValue);
				Object convertedValue = resolvedValue;
				boolean convertible = bw.isWritableProperty(propertyName) &&
						!PropertyAccessorUtils.isNestedOrIndexedProperty(propertyName);
				if (convertible) {
					convertedValue = convertForProperty(resolvedValue, propertyName, bw, converter);
				}
				// Possibly store converted value in merged bean definition,
				// in order to avoid re-conversion for every created bean instance.
				if (resolvedValue == originalValue) {
					if (convertible) {
						pv.setConvertedValue(convertedValue);
					}
					deepCopy.add(pv);
				}
				else if (convertible && originalValue instanceof TypedStringValue &&
						!((TypedStringValue) originalValue).isDynamic() &&
						!(convertedValue instanceof Collection || ObjectUtils.isArray(convertedValue))) {
					pv.setConvertedValue(convertedValue);
					deepCopy.add(pv);
				}
				else {
					resolveNecessary = true;
					deepCopy.add(new PropertyValue(pv, convertedValue));
				}
			}
		}
		if (mpvs != null && !resolveNecessary) {
			mpvs.setConverted();
		}
		// Set our (possibly massaged) deep copy.
		try {
			// 对bean的各个属性进行设置，调用setter方法（太长了不具体分析了）
			bw.setPropertyValues(new MutablePropertyValues(deepCopy));
		}
		catch (BeansException ex) {
			throw new BeanCreationException(
					mbd.getResourceDescription(), beanName, "Error setting property values", ex);
		}
	}
// 解析value
	public Object resolveValueIfNecessary(Object argName, Object value) {
		// We must check each value to see whether it requires a runtime reference
		// to another bean to be resolved.
		// value是一个bean
		if (value instanceof RuntimeBeanReference) {
			RuntimeBeanReference ref = (RuntimeBeanReference) value;
			return resolveReference(argName, ref);
		}
		else if (value instanceof RuntimeBeanNameReference) {
			String refName = ((RuntimeBeanNameReference) value).getBeanName();
			refName = String.valueOf(doEvaluate(refName));
			if (!this.beanFactory.containsBean(refName)) {
				throw new BeanDefinitionStoreException(
						"Invalid bean name '" + refName + "' in bean reference for " + argName);
			}
			return refName;
		}
		else if (value instanceof BeanDefinitionHolder) {
			// Resolve BeanDefinitionHolder: contains BeanDefinition with name and aliases.
			BeanDefinitionHolder bdHolder = (BeanDefinitionHolder) value;
			return resolveInnerBean(argName, bdHolder.getBeanName(), bdHolder.getBeanDefinition());
		}
		else if (value instanceof BeanDefinition) {
			// Resolve plain BeanDefinition, without contained name: use dummy name.
			BeanDefinition bd = (BeanDefinition) value;
			String innerBeanName = "(inner bean)" + BeanFactoryUtils.GENERATED_BEAN_NAME_SEPARATOR +
					ObjectUtils.getIdentityHexString(bd);
			return resolveInnerBean(argName, innerBeanName, bd);
		}
		else if (value instanceof ManagedArray) {
			// May need to resolve contained runtime references.
			ManagedArray array = (ManagedArray) value;
			Class<?> elementType = array.resolvedElementType;
			if (elementType == null) {
				String elementTypeName = array.getElementTypeName();
				if (StringUtils.hasText(elementTypeName)) {
					try {
						elementType = ClassUtils.forName(elementTypeName, this.beanFactory.getBeanClassLoader());
						array.resolvedElementType = elementType;
					}
					catch (Throwable ex) {
						// Improve the message by showing the context.
						throw new BeanCreationException(
								this.beanDefinition.getResourceDescription(), this.beanName,
								"Error resolving array type for " + argName, ex);
					}
				}
				else {
					elementType = Object.class;
				}
			}
			return resolveManagedArray(argName, (List<?>) value, elementType);
		}
		// value是一个list
		else if (value instanceof ManagedList) {
			// May need to resolve contained runtime references.
			return resolveManagedList(argName, (List<?>) value);
		}
		// set
		else if (value instanceof ManagedSet) {
			// May need to resolve contained runtime references.
			return resolveManagedSet(argName, (Set<?>) value);
		}
		// map
		else if (value instanceof ManagedMap) {
			// May need to resolve contained runtime references.
			return resolveManagedMap(argName, (Map<?, ?>) value);
		}
		// value是一个Properties
		else if (value instanceof ManagedProperties) {
			Properties original = (Properties) value;
			Properties copy = new Properties();
			for (Map.Entry<Object, Object> propEntry : original.entrySet()) {
				Object propKey = propEntry.getKey();
				Object propValue = propEntry.getValue();
				if (propKey instanceof TypedStringValue) {
					propKey = evaluate((TypedStringValue) propKey);
				}
				if (propValue instanceof TypedStringValue) {
					propValue = evaluate((TypedStringValue) propValue);
				}
				copy.put(propKey, propValue);
			}
			return copy;
		}
		else if (value instanceof TypedStringValue) {
			// Convert value to target type here.
			TypedStringValue typedStringValue = (TypedStringValue) value;
			Object valueObject = evaluate(typedStringValue);
			try {
				Class<?> resolvedTargetType = resolveTargetType(typedStringValue);
				if (resolvedTargetType != null) {
					return this.typeConverter.convertIfNecessary(valueObject, resolvedTargetType);
				}
				else {
					return valueObject;
				}
			}
			catch (Throwable ex) {
				// Improve the message by showing the context.
				throw new BeanCreationException(
						this.beanDefinition.getResourceDescription(), this.beanName,
						"Error converting typed String value for " + argName, ex);
			}
		}
		else {
			return evaluate(value);
		}
	}

完成bean的属性注入后，最后对bean进行初始化，最后对initializeBean方法进行分析：

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protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
		if (System.getSecurityManager() != null) {
			AccessController.doPrivileged(new PrivilegedAction<Object>() {
				@Override
				public Object run() {
					// 调用aware接口方法
					invokeAwareMethods(beanName, bean);
					return null;
				}
			}, getAccessControlContext());
		}
		else {
			invokeAwareMethods(beanName, bean);
		}
		Object wrappedBean = bean;
		if (mbd == null || !mbd.isSynthetic()) {
			// BeanPostProcessors的applyBeanPostProcessorsBeforeInitialization方法
			wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
		}
		try {
			// init方法调用
			invokeInitMethods(beanName, wrappedBean, mbd);
		}
		catch (Throwable ex) {
			throw new BeanCreationException(
					(mbd != null ? mbd.getResourceDescription() : null),
					beanName, "Invocation of init method failed", ex);
		}
		if (mbd == null || !mbd.isSynthetic()) {
			// applyBeanPostProcessorsAfterInitialization方法
			wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
		}
		return wrappedBean;
	}
	// aware方法调用
	private void invokeAwareMethods(final String beanName, final Object bean) {
		if (bean instanceof Aware) {
			if (bean instanceof BeanNameAware) {
				((BeanNameAware) bean).setBeanName(beanName);
			}
			if (bean instanceof BeanClassLoaderAware) {
				((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
			}
			if (bean instanceof BeanFactoryAware) {
				((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
			}
		}
	}
	// postProcessBeforeInitialization方法
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
			throws BeansException {
		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			result = beanProcessor.postProcessBeforeInitialization(result, beanName);
			if (result == null) {
				return result;
			}
		}
		return result;
	}
	// init方法调用
	protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
			throws Throwable {
		boolean isInitializingBean = (bean instanceof InitializingBean);
		if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
			if (logger.isDebugEnabled()) {
				logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
			}
			if (System.getSecurityManager() != null) {
				try {
					AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
						@Override
						public Object run() throws Exception {
							((InitializingBean) bean).afterPropertiesSet();
							return null;
						}
					}, getAccessControlContext());
				}
				catch (PrivilegedActionException pae) {
					throw pae.getException();
				}
			}
			else {
				// afterPropertiesSet方法调用
				((InitializingBean) bean).afterPropertiesSet();
			}
		}
		if (mbd != null) {
			// init方法调用
			String initMethodName = mbd.getInitMethodName();
			if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
					!mbd.isExternallyManagedInitMethod(initMethodName)) {
				invokeCustomInitMethod(beanName, bean, mbd);
			}
		}
	}
	// postProcessAfterInitialization方法
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
			throws BeansException {
		Object result = existingBean;
		for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
			result = beanProcessor.postProcessAfterInitialization(result, beanName);
			if (result == null) {
				return result;
			}
		}
		return result;
	}

整个过程大概流程简单分析了下，具体的方法细节有待进一步研究，时序图如下：
img

谢谢大佬的打赏!