经过前面几篇的分析，相信大家对Spring中容器功能有了简单的了解，在前面的章节中我们一直以BeanFactory接口以及它的默认实现类XmlBeanFactory为例进行分析。但是，Spring中还提供了另一个接口ApplicationContext，用于扩展BeanFactory中现有的功能。
ApplicationContext和BeanFactory两者都是用于加载Bean的，但是相比之下，ApplicationContext提供了更多的扩展功能，ApplicationContext包含了BeanFactory的所有功能。绝大多数典型的企业应用和系统，ApplicationContext就是你需要使用的。
首先看看使用这两个不同的类去加载配置文件在写法上的不同。
- 使用BeanFactory方式加载XML
BeanFactory bf = new XmlBeanFactory(new ClassPathResource("beanFactoryTest.xml"));
- 使用ApplicationContext方式加载XML
ApplicationContext bf = new ClassPathXmlApplicationContext("beanFactoryTest.xml"));
一：整体功能分析
本文以ClassPathXmlApplicationContext作为切入点，开始对整体功能进行分析。
public class ClassPathXmlApplicationContext extends AbstractXmlApplicationContext { private Resource[] configResources; /** * Create a new ClassPathXmlApplicationContext for bean-style configuration. * @see #setConfigLocation * @see #setConfigLocations * @see #afterPropertiesSet() */ public ClassPathXmlApplicationContext() { } /** * Create a new ClassPathXmlApplicationContext for bean-style configuration. * @param parent the parent context * @see #setConfigLocation * @see #setConfigLocations * @see #afterPropertiesSet() */ public ClassPathXmlApplicationContext(ApplicationContext parent) { super(parent); } /** * Create a new ClassPathXmlApplicationContext, loading the definitions * from the given XML file and automatically refreshing the context. * @param configLocation resource location * @throws BeansException if context creation failed */ public ClassPathXmlApplicationContext(String configLocation) throws BeansException { this(new String[] {configLocation}, true, null); } /** * Create a new ClassPathXmlApplicationContext, loading the definitions * from the given XML files and automatically refreshing the context. * @param configLocations array of resource locations * @throws BeansException if context creation failed */ public ClassPathXmlApplicationContext(String... configLocations) throws BeansException { this(configLocations, true, null); } /** * Create a new ClassPathXmlApplicationContext with the given parent, * loading the definitions from the given XML files and automatically * refreshing the context. * @param configLocations array of resource locations * @param parent the parent context * @throws BeansException if context creation failed */ public ClassPathXmlApplicationContext(String[] configLocations, ApplicationContext parent) throws BeansException { this(configLocations, true, parent); } /** * Create a new ClassPathXmlApplicationContext, loading the definitions * from the given XML files. * @param configLocations array of resource locations * @param refresh whether to automatically refresh the context, * loading all bean definitions and creating all singletons. * Alternatively, call refresh manually after further configuring the context. * @throws BeansException if context creation failed * @see #refresh() */ public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh) throws BeansException { this(configLocations, refresh, null); } /** * Create a new ClassPathXmlApplicationContext with the given parent, * loading the definitions from the given XML files. * @param configLocations array of resource locations * @param refresh whether to automatically refresh the context, * loading all bean definitions and creating all singletons. * Alternatively, call refresh manually after further configuring the context. * @param parent the parent context * @throws BeansException if context creation failed * @see #refresh() */ public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent) throws BeansException { super(parent); setConfigLocations(configLocations); if (refresh) { refresh(); } } /** * Create a new ClassPathXmlApplicationContext, loading the definitions * from the given XML file and automatically refreshing the context. * <p>This is a convenience method to load class path resources relative to a * given Class. For full flexibility, consider using a GenericApplicationContext * with an XmlBeanDefinitionReader and a ClassPathResource argument. * @param path relative (or absolute) path within the class path * @param clazz the class to load resources with (basis for the given paths) * @throws BeansException if context creation failed * @see org.springframework.core.io.ClassPathResource#ClassPathResource(String, Class) * @see org.springframework.context.support.GenericApplicationContext * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader */ public ClassPathXmlApplicationContext(String path, Class<?> clazz) throws BeansException { this(new String[] {path}, clazz); } /** * Create a new ClassPathXmlApplicationContext, loading the definitions * from the given XML files and automatically refreshing the context. * @param paths array of relative (or absolute) paths within the class path * @param clazz the class to load resources with (basis for the given paths) * @throws BeansException if context creation failed * @see org.springframework.core.io.ClassPathResource#ClassPathResource(String, Class) * @see org.springframework.context.support.GenericApplicationContext * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader */ public ClassPathXmlApplicationContext(String[] paths, Class<?> clazz) throws BeansException { this(paths, clazz, null); } /** * Create a new ClassPathXmlApplicationContext with the given parent, * loading the definitions from the given XML files and automatically * refreshing the context. * @param paths array of relative (or absolute) paths within the class path * @param clazz the class to load resources with (basis for the given paths) * @param parent the parent context * @throws BeansException if context creation failed * @see org.springframework.core.io.ClassPathResource#ClassPathResource(String, Class) * @see org.springframework.context.support.GenericApplicationContext * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader */ public ClassPathXmlApplicationContext(String[] paths, Class<?> clazz, ApplicationContext parent) throws BeansException { super(parent); Assert.notNull(paths, "Path array must not be null"); Assert.notNull(clazz, "Class argument must not be null"); this.configResources = new Resource[paths.length]; for (int i = 0; i < paths.length; i++) { this.configResources[i] = new ClassPathResource(paths[i], clazz); } refresh(); } @Override protected Resource[] getConfigResources() { return this.configResources; } }
（1）setConfigLocations(configLocations) 语句
public abstract class AbstractRefreshableConfigApplicationContext extends AbstractRefreshableApplicationContext implements BeanNameAware, InitializingBean { private String[] configLocations; private boolean setIdCalled = false; /** * Create a new AbstractRefreshableConfigApplicationContext with no parent. */ public AbstractRefreshableConfigApplicationContext() { } /** * Create a new AbstractRefreshableConfigApplicationContext with the given parent context. * @param parent the parent context */ public AbstractRefreshableConfigApplicationContext(ApplicationContext parent) { super(parent); } /** * Set the config locations for this application context in init-param style, * i.e. with distinct locations separated by commas, semicolons or whitespace. * <p>If not set, the implementation may use a default as appropriate. */ public void setConfigLocation(String location) { setConfigLocations(StringUtils.tokenizeToStringArray(location, CONFIG_LOCATION_DELIMITERS)); } /** * Set the config locations for this application context. * <p>If not set, the implementation may use a default as appropriate. */ public void setConfigLocations(String... locations) { if (locations != null) { Assert.noNullElements(locations, "Config locations must not be null"); this.configLocations = new String[locations.length]; for (int i = 0; i < locations.length; i++) { this.configLocations[i] = resolvePath(locations[i]).trim(); } } else { this.configLocations = null; } } /** * Return an array of resource locations, referring to the XML bean definition * files that this context should be built with. Can also include location * patterns, which will get resolved via a ResourcePatternResolver. * <p>The default implementation returns {@code null}. Subclasses can override * this to provide a set of resource locations to load bean definitions from. * @return an array of resource locations, or {@code null} if none * @see #getResources * @see #getResourcePatternResolver */ protected String[] getConfigLocations() { return (this.configLocations != null ? this.configLocations : getDefaultConfigLocations()); } /** * Return the default config locations to use, for the case where no * explicit config locations have been specified. * <p>The default implementation returns {@code null}, * requiring explicit config locations. * @return an array of default config locations, if any * @see #setConfigLocations */ protected String[] getDefaultConfigLocations() { return null; } /** * Resolve the given path, replacing placeholders with corresponding * environment property values if necessary. Applied to config locations. * @param path the original file path * @return the resolved file path * @see org.springframework.core.env.Environment#resolveRequiredPlaceholders(String) */ protected String resolvePath(String path) { return getEnvironment().resolveRequiredPlaceholders(path); } @Override public void setId(String id) { super.setId(id); this.setIdCalled = true; } /** * Sets the id of this context to the bean name by default, * for cases where the context instance is itself defined as a bean. */ @Override public void setBeanName(String name) { if (!this.setIdCalled) { super.setId(name); setDisplayName("ApplicationContext '" + name + "'"); } } /** * Triggers {@link #refresh()} if not refreshed in the concrete context's * constructor already. */ @Override public void afterPropertiesSet() { if (!isActive()) { refresh(); } } }
此函数主要用于解析给定的路径数组，当然，如果数组中包含特殊符号，如${var}，那么在resolvePath中会搜寻匹配的系统变量并替换。
（2）扩展功能
设置了路径后，便可以根据路径做配置文件的解析以及各种功能的实现了。可以说refresh函数中包含了几乎ApplicationContext中提供的全部功能，而且此函数中逻辑非常清晰明了，使我们很容易分析对应的层次及逻辑。
org.springframework.context.support.AbstractApplicationContext
@Override public void refresh() throws BeansException, IllegalStateException { synchronized (this.startupShutdownMonitor) { // Prepare this context for refreshing. //准备刷新的上下文环境
prepareRefresh(); // Tell the subclass to refresh the internal bean factory. //初始化BeanFactory，并进行XML文件读取
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory(); // Prepare the bean factory for use in this context. //对BeanFactory进行各种功能填充
prepareBeanFactory(beanFactory); try { // Allows post-processing of the bean factory in context subclasses. //子类覆盖方法做额外的处理
postProcessBeanFactory(beanFactory); // Invoke factory processors registered as beans in the context. //激活各种BeanFactory处理器
invokeBeanFactoryPostProcessors(beanFactory); // Register bean processors that intercept bean creation. //注册拦截Bean创建的Bean处理器，这里只是注册，真正的调用是在getBean时候
registerBeanPostProcessors(beanFactory); // Initialize message source for this context. //为上下文初始化Message源，即不同语言的消息体，国际化处理
initMessageSource(); // Initialize event multicaster for this context. //初始化应用消息广播器，并放入"applicationEventMulticaster" bean中
initApplicationEventMulticaster(); // Initialize other special beans in specific context subclasses. //留给子类来初始化其它的Bean
onRefresh(); // Check for listener beans and register them. //在所有注册的bean中查找Listener bean，注册到消息广播中
registerListeners(); // Instantiate all remaining (non-lazy-init) singletons. //初始化剩下的单实例（非惰性的）
finishBeanFactoryInitialization(beanFactory); // Last step: publish corresponding event. //完成刷新过程，通知生命周期处理器lifecycleProcessor刷新过程，同时发出ContextRefreshEvent通知别人
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(); } } }
下面概况一下ClassPathXmlApplicationContext初始化的步骤，并从中解析一下它为我们提供的功能。
（1）初始化前的准备工作，例如对系统属性或者环境变量进行准备及验证。
在某种情况下项目的使用需要读取某些系统变量，二这个变量的设置很可能会影响系统的正确性，那么ClassPathXmlApplicationContext为我们提供的这个准备函数就显得非常必要，它可以在Spring启动的时候提前对必须的变量进行存在性验证。
（2）初始化BeanFactory，并进行XML文件读取。
之前有提到ClassPathXmlApplicationContext包含着BeanFactory所提供的一切特征，那么这一步骤中将会复用BeanFactory中的配置文件读取解析及其它功能，这一步之后，ClassPathXmlApplicationContext实际上就已经包含了BeanFactory所提供的功能，也就是可以进行Bean的提取等基础操作了。
（3）对BeanFactory进行各种功能填充。
是否允许bean覆盖，是否允许循环依赖等。
（4）子类覆盖方法做额外的处理
Spring之所以强大，为世人所推崇，除了它功能上为大家提供了便利外，还有一方面是它的完美架构，开放式的架构让使用它的程序员很容易根据业务需要扩展已经存在的功能。这种开放式的设计在Spring中随处可见，例如在本例中就提供了一个空的函数实现postProcessBeanFactory来方便程序员在业务上做进一步的扩展。
（5）激活各种BeanFactory处理器
（6）注册拦截bean创建的bean处理器，这里只是注册，真正的调用是在getBean时候。
（7）为上下文初始化Message源，即对不同语言的消息体进行国际化处理。
（8）初始化应用消息广播器，并放入“applicationEventMulticaster” bean中。
（9）留给子类来初始化其它的bean。
（10）在所有注册的bean中查找listener bean，注册到消息广播器中。
（11）初始化剩下的单实例（非惰性的）.
（12）完成刷新过程，通知生命周期处理器lifecycleProcessor刷新过程，同时发出ContextRefreshEvent通知别人。
二：各功能分析
（1）AbstractApplicationContext 类中 prepareRefresh 方法
prepareRefresh函数主要是做些准备工作，例如对系统属性及环境变量的初始化及验证。
/** * Prepare this context for refreshing, setting its startup date and * active flag as well as performing any initialization of property sources. */ protected void prepareRefresh() { this.startupDate = System.currentTimeMillis(); this.closed.set(false); this.active.set(true); if (logger.isInfoEnabled()) { logger.info("Refreshing " + this); } // Initialize any placeholder property sources in the context environment initPropertySources(); // Validate that all properties marked as required are resolvable // see ConfigurablePropertyResolver#setRequiredProperties getEnvironment().validateRequiredProperties(); // Allow for the collection of early ApplicationEvents, // to be published once the multicaster is available... this.earlyApplicationEvents = new LinkedHashSet<ApplicationEvent>(); }
（2）加载BeanFactory
obtainFreshBeanFactory 方法从字面理解是获取BeanFactory。ApplicationContext是对BeanFactory的功能上的扩展，不但包含了BeanFactory的全部功能，更在其基础上添加了大量的扩展应用，那么obtainFreshBeanFactor正是实现BeanFactory的地方，也就是经过这个函数后ApplicationContext就已经拥有了BeanFactory的全部功能。
（2.1）AbstractApplicationContext 类中 prepareRefresh 方法
/** * Tell the subclass to refresh the internal bean factory. * @return the fresh BeanFactory instance * @see #refreshBeanFactory() * @see #getBeanFactory() */ protected ConfigurableListableBeanFactory obtainFreshBeanFactory() { refreshBeanFactory(); ConfigurableListableBeanFactory beanFactory = getBeanFactory(); if (logger.isDebugEnabled()) { logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory); } return beanFactory; }
//AbstractApplicationContext类中的抽象方法
protected abstract void refreshBeanFactory() throws BeansException, IllegalStateException;
（2.2）AbstractRefreshableApplicationContext 类中实现 refreshBeanFactory 方法
public abstract class AbstractRefreshableApplicationContext extends AbstractApplicationContext { private Boolean allowBeanDefinitionOverriding; private Boolean allowCircularReferences; /** Bean factory for this context */ private DefaultListableBeanFactory beanFactory; /** Synchronization monitor for the internal BeanFactory */ private final Object beanFactoryMonitor = new Object(); /** * Create a new AbstractRefreshableApplicationContext with no parent. */ public AbstractRefreshableApplicationContext() { } /** * Create a new AbstractRefreshableApplicationContext with the given parent context. * @param parent the parent context */ public AbstractRefreshableApplicationContext(ApplicationContext parent) { super(parent); } /** * Set whether it should be allowed to override bean definitions by registering * a different definition with the same name, automatically replacing the former. * If not, an exception will be thrown. Default is "true". * @see org.springframework.beans.factory.support.DefaultListableBeanFactory#setAllowBeanDefinitionOverriding */ public void setAllowBeanDefinitionOverriding(boolean allowBeanDefinitionOverriding) { this.allowBeanDefinitionOverriding = allowBeanDefinitionOverriding; } /** * Set whether to allow circular references between beans - and automatically * try to resolve them. * <p>Default is "true". Turn this off to throw an exception when encountering * a circular reference, disallowing them completely. * @see org.springframework.beans.factory.support.DefaultListableBeanFactory#setAllowCircularReferences */ public void setAllowCircularReferences(boolean allowCircularReferences) { this.allowCircularReferences = allowCircularReferences; } /** * This implementation performs an actual refresh of this context's underlying * bean factory, shutting down the previous bean factory (if any) and * initializing a fresh bean factory for the next phase of the context's lifecycle. */ @Override protected final void refreshBeanFactory() throws BeansException { if (hasBeanFactory()) { destroyBeans(); closeBeanFactory(); } try { DefaultListableBeanFactory beanFactory = createBeanFactory(); beanFactory.setSerializationId(getId()); customizeBeanFactory(beanFactory); loadBeanDefinitions(beanFactory); synchronized (this.beanFactoryMonitor) { this.beanFactory = beanFactory; } } catch (IOException ex) { throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex); } } @Override protected void cancelRefresh(BeansException ex) { synchronized (this.beanFactoryMonitor) { if (this.beanFactory != null) this.beanFactory.setSerializationId(null); } super.cancelRefresh(ex); } @Override protected final void closeBeanFactory() { synchronized (this.beanFactoryMonitor) { this.beanFactory.setSerializationId(null); this.beanFactory = null; } } /** * Determine whether this context currently holds a bean factory, * i.e. has been refreshed at least once and not been closed yet. */ protected final boolean hasBeanFactory() { synchronized (this.beanFactoryMonitor) { return (this.beanFactory != null); } } @Override public final ConfigurableListableBeanFactory getBeanFactory() { synchronized (this.beanFactoryMonitor) { if (this.beanFactory == null) { throw new IllegalStateException("BeanFactory not initialized or already closed - " + "call 'refresh' before accessing beans via the ApplicationContext"); } return this.beanFactory; } } /** * Overridden to turn it into a no-op: With AbstractRefreshableApplicationContext, * {@link #getBeanFactory()} serves a strong assertion for an active context anyway. */ @Override protected void assertBeanFactoryActive() { } /** * Create an internal bean factory for this context. * Called for each {@link #refresh()} attempt. * <p>The default implementation creates a * {@link org.springframework.beans.factory.support.DefaultListableBeanFactory} * with the {@linkplain #getInternalParentBeanFactory() internal bean factory} of this * context's parent as parent bean factory. Can be overridden in subclasses, * for example to customize DefaultListableBeanFactory's settings. * @return the bean factory for this context * @see org.springframework.beans.factory.support.DefaultListableBeanFactory#setAllowBeanDefinitionOverriding * @see org.springframework.beans.factory.support.DefaultListableBeanFactory#setAllowEagerClassLoading * @see org.springframework.beans.factory.support.DefaultListableBeanFactory#setAllowCircularReferences * @see org.springframework.beans.factory.support.DefaultListableBeanFactory#setAllowRawInjectionDespiteWrapping */ protected DefaultListableBeanFactory createBeanFactory() { return new DefaultListableBeanFactory(getInternalParentBeanFactory()); } /** * Customize the internal bean factory used by this context. * Called for each {@link #refresh()} attempt. * <p>The default implementation applies this context's * {@linkplain #setAllowBeanDefinitionOverriding "allowBeanDefinitionOverriding"} * and {@linkplain #setAllowCircularReferences "allowCircularReferences"} settings, * if specified. Can be overridden in subclasses to customize any of * {@link DefaultListableBeanFactory}'s settings. * @param beanFactory the newly created bean factory for this context * @see DefaultListableBeanFactory#setAllowBeanDefinitionOverriding * @see DefaultListableBeanFactory#setAllowCircularReferences * @see DefaultListableBeanFactory#setAllowRawInjectionDespiteWrapping * @see DefaultListableBeanFactory#setAllowEagerClassLoading */ protected void customizeBeanFactory(DefaultListableBeanFactory beanFactory) { if (this.allowBeanDefinitionOverriding != null) { beanFactory.setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding); } if (this.allowCircularReferences != null) { beanFactory.setAllowCircularReferences(this.allowCircularReferences); } } /** * Load bean definitions into the given bean factory, typically through * delegating to one or more bean definition readers. * @param beanFactory the bean factory to load bean definitions into * @throws BeansException if parsing of the bean definitions failed * @throws IOException if loading of bean definition files failed * @see org.springframework.beans.factory.support.PropertiesBeanDefinitionReader * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader */ protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException; }
（2.3）customizeBeanFactory 方法（见2.2）
该方法开始了对BeanFactory的扩展，在基本容器的基础上，增加了是否允许覆盖同名称的不同定义的对象，是否允许bean之间存在循环依赖。
是否允许覆盖和允许依赖这里只是判断了是否为空，如果不为空要进行设置，但是并没有看到在哪里进行设置，究竟这个设置是在哪里进行设置的呢？使用子类覆盖方法，例如：
（2.4）加载BeanDefinition
第一步中提到了将ClassPathXmlApplicationContext与XmlBeanFactory创建的对比，在实现配置文件的加载功能中除了我们在第一步中已经初始化的DefaultListableBeanFactory外，还需要XmlBeanDefinitionReader来读取XML，那么在这个步骤中首先要做的就是初始化XmlBeanDefinitionReader。
public abstract class AbstractXmlApplicationContext extends AbstractRefreshableConfigApplicationContext { private boolean validating = true; /** * Create a new AbstractXmlApplicationContext with no parent. */ public AbstractXmlApplicationContext() { } /** * Create a new AbstractXmlApplicationContext with the given parent context. * @param parent the parent context */ public AbstractXmlApplicationContext(ApplicationContext parent) { super(parent); } /** * Set whether to use XML validation. Default is {@code true}. */ public void setValidating(boolean validating) { this.validating = validating; } /** * Loads the bean definitions via an XmlBeanDefinitionReader. * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader * @see #initBeanDefinitionReader * @see #loadBeanDefinitions */ @Override protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException { // Create a new XmlBeanDefinitionReader for the given BeanFactory. XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); // Configure the bean definition reader with this context's // resource loading environment. beanDefinitionReader.setEnvironment(this.getEnvironment()); beanDefinitionReader.setResourceLoader(this); beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this)); // Allow a subclass to provide custom initialization of the reader, // then proceed with actually loading the bean definitions. initBeanDefinitionReader(beanDefinitionReader); loadBeanDefinitions(beanDefinitionReader); } /** * Initialize the bean definition reader used for loading the bean * definitions of this context. Default implementation is empty. * <p>Can be overridden in subclasses, e.g. for turning off XML validation * or using a different XmlBeanDefinitionParser implementation. * @param reader the bean definition reader used by this context * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader#setDocumentReaderClass */ protected void initBeanDefinitionReader(XmlBeanDefinitionReader reader) { reader.setValidating(this.validating); } /** * Load the bean definitions with the given XmlBeanDefinitionReader. * <p>The lifecycle of the bean factory is handled by the {@link #refreshBeanFactory} * method; hence this method is just supposed to load and/or register bean definitions. * @param reader the XmlBeanDefinitionReader to use * @throws BeansException in case of bean registration errors * @throws IOException if the required XML document isn't found * @see #refreshBeanFactory * @see #getConfigLocations * @see #getResources * @see #getResourcePatternResolver */ protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException { Resource[] configResources = getConfigResources(); if (configResources != null) { reader.loadBeanDefinitions(configResources); } String[] configLocations = getConfigLocations(); if (configLocations != null) { reader.loadBeanDefinitions(configLocations); } } /** * Return an array of Resource objects, referring to the XML bean definition * files that this context should be built with. * <p>The default implementation returns {@code null}. Subclasses can override * this to provide pre-built Resource objects rather than location Strings. * @return an array of Resource objects, or {@code null} if none * @see #getConfigLocations() */ protected Resource[] getConfigResources() { return null; } }
在loadBeanDefinitions（XmlBeanDefinitionReader reader）方法前初始化了DefaultListableBeanFactory和XmlBeanDefinitionReader后就可以进行配置文件的读取了。
使用XmlBeanDefinitionReader的loadBeanDefinitions方法进行配置文件的加载机注册，相信大家已经不陌生，这完全是开始BeanFactory的套路。因为在XmlBeanDefinitionReader中已经将之前初始化的DefaultListableBeanFactory注册进去了，所以XmlBeanDefinitionReader所读取的BeanDefinitionHolder都会注册到DefaultListableBeanFactory中，也就是经过此步骤，类型DefaultListableBeanFactory的变量beanFactory已经包含了所有解析好的配置。
（3）prepareBeanFactory 方法
进入函数prepareBeanFactory前，Spring已经完成了对配置的解析，而ApplicationContext在功能的扩展也由此展开。
/** * Configure the factory's standard context characteristics, * such as the context's ClassLoader and post-processors. * @param beanFactory the BeanFactory to configure */ protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) { // Tell the internal bean factory to use the context's class loader etc. beanFactory.setBeanClassLoader(getClassLoader()); //设置beanFactory的表达式语言处理器，Spring3增加了表达式语言的支持
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader())); //为beanFactory增加了一个默认的propertyEditor，这个主意是对bean的属性等设置管理的一个工具
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment())); // Configure the bean factory with context callbacks. //设置了几个忽略自动装配的接口
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this)); beanFactory.ignoreDependencyInterface(EnvironmentAware.class); beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class); beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class); beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class); beanFactory.ignoreDependencyInterface(MessageSourceAware.class); beanFactory.ignoreDependencyInterface(ApplicationContextAware.class); // BeanFactory interface not registered as resolvable type in a plain factory. // MessageSource registered (and found for autowiring) as a bean.
//设置了几个自动装配的特殊规则 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.
//增加对AspectJ的支持
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())); } // Register default environment beans.
//添加默认的系统环境bean
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()); } }
（3.1）SPEL
（3.2）添加ApplicationContextAwareProcessor处理器
对于beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this))其实主要目的就是注册个BeanPostProcessor，而真正的逻辑还是在ApplicationContextAwareProcessor中。
ApplicationContextAwareProcessor实现BeanPostProcessor接口，我们回顾下之前讲过的内容，在bean实例化的时候，也就是Spring激活bean的init-method的前后，会调用BeanPostProcessor的postProcessBeforeInitialization方法和postProcessAfterInitialization方法。同样，对于ApplicationContextAwareProcessor我们也关心这两个方法。
class ApplicationContextAwareProcessor implements BeanPostProcessor { private final ConfigurableApplicationContext applicationContext; private final StringValueResolver embeddedValueResolver; /** * Create a new ApplicationContextAwareProcessor for the given context. */ public ApplicationContextAwareProcessor(ConfigurableApplicationContext applicationContext) { this.applicationContext = applicationContext; this.embeddedValueResolver = new EmbeddedValueResolver(applicationContext.getBeanFactory()); } @Override public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException { AccessControlContext acc = null; if (System.getSecurityManager() != null && (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware || bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware || bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) { acc = this.applicationContext.getBeanFactory().getAccessControlContext(); } if (acc != null) { AccessController.doPrivileged(new PrivilegedAction<Object>() { @Override public Object run() { invokeAwareInterfaces(bean); return null; } }, acc); } else { invokeAwareInterfaces(bean); } return bean; } private void invokeAwareInterfaces(Object bean) { if (bean instanceof Aware) { if (bean instanceof EnvironmentAware) { ((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment()); } if (bean instanceof EmbeddedValueResolverAware) { ((EmbeddedValueResolverAware) bean).setEmbeddedValueResolver(this.embeddedValueResolver); } if (bean instanceof ResourceLoaderAware) { ((ResourceLoaderAware) bean).setResourceLoader(this.applicationContext); } if (bean instanceof ApplicationEventPublisherAware) { ((ApplicationEventPublisherAware) bean).setApplicationEventPublisher(this.applicationContext); } if (bean instanceof MessageSourceAware) { ((MessageSourceAware) bean).setMessageSource(this.applicationContext); } if (bean instanceof ApplicationContextAware) { ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext); } } } @Override public Object postProcessAfterInitialization(Object bean, String beanName) { return bean; } }
postProcessBeforeInitialization方法中调用了invokeAwareInterfaces。从invokeAwareInterfaces方法中，我们或许已经或多或少了解了Spring的用意，实现这些Aware接口的bean在被初始化之后，可以取得一些对应的资源。
（3.3）设置忽略依赖
当Spring将ApplicationContextAwareProcessor注册后，那么在invokeAwareInterfaces方法中间接调用的Aware类已经不是普通的bean了，如ResourceLoaderAware，ApplicationEventPublisherAware等，那么当然需要在Spring做bean的依赖注入的时候忽略它们。而ignoreDependencyInterface的作用正是在此。
（3.4）注册依赖
Spring中有了忽略依赖的功能，当然也必不可少地会有注册依赖的功能。
当注册了依赖解析后，例如当注册了对BeanFactory.class的解析依赖后，当bean的属性注入的时候，一旦检测到属性为BeanFactory类型便会将beanFactory的实例注入进去。
（3.5）BeanFactory的后处理
BeanFactory作为Spring中容器功能的基础，用于存放所有已经加载的bean，为了保证程序上的高可扩展性，Spring针对BeanFactory做了大量的扩展，比如我们熟知的PostProcessor等都是在这里实现的。
（3.5.0）BeanFactoryPostProcessor
public interface BeanFactoryPostProcessor { /** * Modify the application context's internal bean factory after its standard * initialization. All bean definitions will have been loaded, but no beans * will have been instantiated yet. This allows for overriding or adding * properties even to eager-initializing beans. * @param beanFactory the bean factory used by the application context * @throws org.springframework.beans.BeansException in case of errors */ void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException; }
public interface BeanPostProcessor { /** * Apply this BeanPostProcessor to the given new bean instance <i>before</i> any bean * initialization callbacks (like InitializingBean's {@code afterPropertiesSet} * or a custom init-method). The bean will already be populated with property values. * The returned bean instance may be a wrapper around the original. * @param bean the new bean instance * @param beanName the name of the bean * @return the bean instance to use, either the original or a wrapped one; * if {@code null}, no subsequent BeanPostProcessors will be invoked * @throws org.springframework.beans.BeansException in case of errors * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet */ Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException; /** * Apply this BeanPostProcessor to the given new bean instance <i>after</i> any bean * initialization callbacks (like InitializingBean's {@code afterPropertiesSet} * or a custom init-method). The bean will already be populated with property values. * The returned bean instance may be a wrapper around the original. * <p>In case of a FactoryBean, this callback will be invoked for both the FactoryBean * instance and the objects created by the FactoryBean (as of Spring 2.0). The * post-processor can decide whether to apply to either the FactoryBean or created * objects or both through corresponding {@code bean instanceof FactoryBean} checks. * <p>This callback will also be invoked after a short-circuiting triggered by a * {@link InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation} method, * in contrast to all other BeanPostProcessor callbacks. * @param bean the new bean instance * @param beanName the name of the bean * @return the bean instance to use, either the original or a wrapped one; * if {@code null}, no subsequent BeanPostProcessors will be invoked * @throws org.springframework.beans.BeansException in case of errors * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet * @see org.springframework.beans.factory.FactoryBean */ Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException; }
（3.5.1）激活注册的BeanFactoryPostProcessor
BeanFactoryPostProcessor接口跟BeanPostProcessor类似，可以对bean的定义（配置元数据）进行处理。也就是说，Spring Ioc容器允许BeanFactoryPostProcessor在容器实例化任何其他的bean之前读取配置元数据，并有可能修改它。如果你愿意，你可以配置多个BeanFactoryPostProcessor。你还能通过设置order属性来控制BeanFactoryPostProcessor的执行次序（仅当BeanFactoryPostProcessor实现了ordered接口时你才可以设置此属性，因此在实现BeanFactoryPostProcessor时，就应当考虑实现Ordered接口）。
如果你想改变实际的bean实例（例如从配置元数据创建的对象），那么你最好使用BeanPostProcessor。同样，BeanFactoryPostProcessor的作用域范围是容器级的，它只和你所使用的容器有关。如果你在容器中定义一个BeanFactoryPostProcessor，它仅仅对此容器中的bean进行后置处理。BeanFactoryPostProcessor不会对定义在另一个容器中的bean进行后置处理，即使这两个容器都是在同一层次上。
（3.5.2）BeanFactoryPostProcessor的典型应用：PropertyPlaceholderConfigurer
这个“mesHandler”只不过是Spring框架管理的一个bean，并没有被别的bean或者对象引用，Spring的beanFactory是怎么知道要从这个bean中获取配置信息的呢？
（3.5.3）激活BeanFactoryPostProcessor
/** * Instantiate and invoke all registered BeanFactoryPostProcessor beans, * respecting explicit order if given. * <p>Must be called before singleton instantiation. */ protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors()); // Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime // (e.g. through an @Bean method registered by ConfigurationClassPostProcessor) if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) { beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory)); beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader())); } }
/** * Delegate for AbstractApplicationContext's post-processor handling. * * @author Juergen Hoeller * @since 4.0 */ class PostProcessorRegistrationDelegate { public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // Invoke BeanDefinitionRegistryPostProcessors first, if any. Set<String> processedBeans = new HashSet<String>();
//对BeanDefinitionRegistry类型的处理 if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>(); List<BeanDefinitionRegistryPostProcessor> registryPostProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
//硬编码注册的后处理器 for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryPostProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; registryPostProcessor.postProcessBeanDefinitionRegistry(registry); registryPostProcessors.add(registryPostProcessor); } else { regularPostProcessors.add(postProcessor); } } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! // Separate between BeanDefinitionRegistryPostProcessors that implement // PriorityOrdered, Ordered, and the rest. String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. List<BeanDefinitionRegistryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>(); for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(beanFactory, priorityOrderedPostProcessors); registryPostProcessors.addAll(priorityOrderedPostProcessors); invokeBeanDefinitionRegistryPostProcessors(priorityOrderedPostProcessors, registry); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); List<BeanDefinitionRegistryPostProcessor> orderedPostProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>(); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); } } sortPostProcessors(beanFactory, orderedPostProcessors); registryPostProcessors.addAll(orderedPostProcessors); invokeBeanDefinitionRegistryPostProcessors(orderedPostProcessors, registry); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. boolean reiterate = true; while (reiterate) { reiterate = false; postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { if (!processedBeans.contains(ppName)) { BeanDefinitionRegistryPostProcessor pp = beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class); registryPostProcessors.add(pp); processedBeans.add(ppName); pp.postProcessBeanDefinitionRegistry(registry); reiterate = true; } } } // Now, invoke the postProcessBeanFactory callback of all processors handled so far. invokeBeanFactoryPostProcessors(registryPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); } else { // Invoke factory processors registered with the context instance. invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, // Ordered, and the rest. List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>(); List<String> orderedPostProcessorNames = new ArrayList<String>(); List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
//对后处理器进行分类 for (String ppName : postProcessorNames) { if (processedBeans.contains(ppName)) { // skip - already processed in first phase above } else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class)); } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } } // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered. sortPostProcessors(beanFactory, priorityOrderedPostProcessors); invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory); // Next, invoke the BeanFactoryPostProcessors that implement Ordered. List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>(); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(beanFactory, orderedPostProcessors); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors. List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>(); for (String postProcessorName : nonOrderedPostProcessorNames) { nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory); // Clear cached merged bean definitions since the post-processors might have // modified the original metadata, e.g. replacing placeholders in values... beanFactory.clearMetadataCache(); } public static void registerBeanPostProcessors( ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) { String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false); // Register BeanPostProcessorChecker that logs an info message when // a bean is created during BeanPostProcessor instantiation, i.e. when // a bean is not eligible for getting processed by all BeanPostProcessors. int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length; beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount)); // Separate between BeanPostProcessors that implement PriorityOrdered, // Ordered, and the rest. List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>(); List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>(); List<String> orderedPostProcessorNames = new ArrayList<String>(); List<String> nonOrderedPostProcessorNames = new ArrayList<String>(); for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); priorityOrderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } else if (beanFactory.isTypeMatch(ppName, Ordered.class)) { orderedPostProcessorNames.add(ppName); } else { nonOrderedPostProcessorNames.add(ppName); } } // First, register the BeanPostProcessors that implement PriorityOrdered. sortPostProcessors(beanFactory, priorityOrderedPostProcessors); registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors); // Next, register the BeanPostProcessors that implement Ordered. List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>(); for (String ppName : orderedPostProcessorNames) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); orderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } sortPostProcessors(beanFactory, orderedPostProcessors); registerBeanPostProcessors(beanFactory, orderedPostProcessors); // Now, register all regular BeanPostProcessors. List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>(); for (String ppName : nonOrderedPostProcessorNames) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); nonOrderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors); // Finally, re-register all internal BeanPostProcessors. sortPostProcessors(beanFactory, internalPostProcessors); registerBeanPostProcessors(beanFactory, internalPostProcessors); // Re-register post-processor for detecting inner beans as ApplicationListeners, // moving it to the end of the processor chain (for picking up proxies etc). beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); } private static void sortPostProcessors(ConfigurableListableBeanFactory beanFactory, List<?> postProcessors) { Comparator<Object> comparatorToUse = null; if (beanFactory instanceof DefaultListableBeanFactory) { comparatorToUse = ((DefaultListableBeanFactory) beanFactory).getDependencyComparator(); } if (comparatorToUse == null) { comparatorToUse = OrderComparator.INSTANCE; } Collections.sort(postProcessors, comparatorToUse); } /** * Invoke the given BeanDefinitionRegistryPostProcessor beans. */ private static void invokeBeanDefinitionRegistryPostProcessors( Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) { for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) { postProcessor.postProcessBeanDefinitionRegistry(registry); } } /** * Invoke the given BeanFactoryPostProcessor beans. */ private static void invokeBeanFactoryPostProcessors( Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) { for (BeanFactoryPostProcessor postProcessor : postProcessors) { postProcessor.postProcessBeanFactory(beanFactory); } } /** * Register the given BeanPostProcessor beans. */ private static void registerBeanPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) { for (BeanPostProcessor postProcessor : postProcessors) { beanFactory.addBeanPostProcessor(postProcessor); } } /** * BeanPostProcessor that logs an info message when a bean is created during * BeanPostProcessor instantiation, i.e. when a bean is not eligible for * getting processed by all BeanPostProcessors. */ private static class BeanPostProcessorChecker implements BeanPostProcessor { private static final Log logger = LogFactory.getLog(BeanPostProcessorChecker.class); private final ConfigurableListableBeanFactory beanFactory; private final int beanPostProcessorTargetCount; public BeanPostProcessorChecker(ConfigurableListableBeanFactory beanFactory, int beanPostProcessorTargetCount) { this.beanFactory = beanFactory; this.beanPostProcessorTargetCount = beanPostProcessorTargetCount; } @Override public Object postProcessBeforeInitialization(Object bean, String beanName) { return bean; } @Override public Object postProcessAfterInitialization(Object bean, String beanName) { if (bean != null && !(bean instanceof BeanPostProcessor) && !isInfrastructureBean(beanName) && this.beanFactory.getBeanPostProcessorCount() < this.beanPostProcessorTargetCount) { if (logger.isInfoEnabled()) { logger.info("Bean '" + beanName + "' of type [" + bean.getClass().getName() + "] is not eligible for getting processed by all BeanPostProcessors " + "(for example: not eligible for auto-proxying)"); } } return bean; } private boolean isInfrastructureBean(String beanName) { if (beanName != null && this.beanFactory.containsBeanDefinition(beanName)) { BeanDefinition bd = this.beanFactory.getBeanDefinition(beanName); return (bd.getRole() == RootBeanDefinition.ROLE_INFRASTRUCTURE); } return false; } } }
AbstractApplicationContext 类中 registerBeanPostProcessors 方法（见上）
/** * Instantiate and invoke all registered BeanPostProcessor beans, * respecting explicit order if given. * <p>Must be called before any instantiation of application beans. */ protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this); }