Spring源码学习之IOC实现原理（二）-ApplicationContext

一.Spring核心组件结构

总的来说Spring共有三个核心组件，分别为Core，Context，Bean.三大核心组件的协同工作主要表现在 ：Bean是包装我们应用程序自定义对象Object的，Object中存有数据，而Context就是为了这些数据存放提供一个生存环境，保存各个 bean之间的对应关系，并且维护好这些对应关系。Context就是一个Bean关系的集合，也就是我们所谓的IOC容器。Core就是Context 在发现、建立、维护Bean之间关系所需要的一些工具，如资源的加载，资源的抽象等。 （《深入分析Java Web技术内幕》）

1.Bean组件

前面介绍的BeanFactory体系就属于Bean组件，位于org.springframework.beans子包factory包下面。这个包主要解决三个问题，Bean的定义，Bean的创建，Bean的解析。

1. org.springframework.beans, 包含了操作java bean的接口和类。This package contains interfaces and classes for manipulating Java beans. It is used by most other Spring packages. ***

2. org.springframework.beans.annotation, 支持包，提供对java 5注解处理bean样式的支持。
3. org.springframework.beans.factory, 实现spring轻量级IoC容器的核心包。***
4. org.springframework.beans.factory.access, 定位和获取bean工程的辅助工具类。
5. org.springframework.beans.factory.access.el,从统一样式的EL 获取spring beanFactory的支持类
6. org.springframework.beans.factory.annotation, 配置基于注解驱动的bean的支持包。***
7. org.springframework.beans.factory.config, bean工厂的SPI接口和配置相关的处理类。
8. org.springframework.beans.factory.parsing, bean definition解析的支持基础类
9. org.springframework.beans.factory.serviceloader, jdk1.6 ServiceLoader基础类的支持包。
10. org.springframework.beans.factory.support,org.springframework.beans.factory包的支持类
11. org.springframework.beans.factory.wiring, 一种决定一个bean实例的元数据的机制。
12. org.springframework.beans.factory.xml, 包含了一个基于xml的beanFactory实现，也包含一个标准的spring-beans的dtd
13. org.springframework.beans.propertyeditors, 属性编辑器，用来将string类型的值转换为object类型，例如：java.util.Properties
14. org.springframework.beans.support,org.springframework.beans的支持包，像：一组bean的排序和保持工具类等

参考资料spring beans源码解读之--总结篇

Bean的定义由BeanDefinition抽象出来，也是IOC容器的内部数据结构。BeanDefinition完整的描述了xml文件中关于<bean>节点的所有信息。当Spring解析一个<bean>节点后，在IOC容器内部就会转换为BeanDefinition对象。而最终实例化时，所使用的对象就是RootBeanDefinition对象。

图片引自Spring3.0核心组件的源码简单分析

Bean的创建，采用的是典型的工厂模式，采用的体系即(一)中所说的BeanFactory体系结构。主要的类是DefaultListableBeanFactory,其完整的实现了IOC容器的功能。

Bean的解析，主要就是对于Spring的配置文件进行解析处理，从中解析出相应的信息以用来生成Bean的对象。 其中主要用于解析的实现类就是DefaultBeanDefinitionDocumentReader。

2.Core组件

Core组件作为Spring的核心组件，其中包含了很多关键类，一个重要的组成部分就是定义了资源的访问方式。如之前用到的ClassPathResource就是其中的一个典型的资源抽象形式。资源的顶级接口为Resource，它继承自InputStreamSource，实现了其getInputStream方法，返回的是InputStream类。这样所有的资源就是通过该方法来获取输入流的。对于资源的加载，也实现了统一，屏蔽了资源提供者。定义了一个资源加载顶级接口 ResourceLoader ，它默认的加载就是DefaultResourceLoader。

2.1InputStreamSource

该接口只有一个抽象方法

public interface InputStreamSource {

    /**
     * Return an {@link InputStream}.
     */
    InputStream getInputStream() throws IOException;

}

2.2 Resource

作为顶级接口，也是再各个类中调用资源时应用最为广泛的接口，充分体现了面向接口编程的思想。

/**
 * Interface for a resource descriptor that abstracts from the actual
 * type of underlying resource, such as a file or class path resource.
 */
public interface Resource extends InputStreamSource {

    boolean exists();
    boolean isReadable();

    boolean isOpen();

    URL getURL() throws IOException;

    URI getURI() throws IOException;

    File getFile() throws IOException;

    long contentLength() throws IOException;

    long lastModified() throws IOException;

    Resource createRelative(String relativePath) throws IOException;

    String getFilename();

    String getDescription();

}

这就是该接口定义的方法，都是显而易见的方法，同时也是对于资源类来说应用最多的方法。

2.3ClassPathResource

/**
     * This implementation opens an InputStream for the given class path resource.
     * @see java.lang.ClassLoader#getResourceAsStream(String)
     * @see java.lang.Class#getResourceAsStream(String)
     */
    @Override
    public InputStream getInputStream() throws IOException {
        InputStream is;
        if (this.clazz != null) {
            is = this.clazz.getResourceAsStream(this.path);
        }
        else if (this.classLoader != null) {
            is = this.classLoader.getResourceAsStream(this.path);
        }
        else {
            is = ClassLoader.getSystemResourceAsStream(this.path);
        }
        if (is == null) {
            throw new FileNotFoundException(getDescription() + " cannot be opened because it does not exist");
        }
        return is;
}

该方法就是ClassPathResource的getInputStream方法，可以发现其主要通过class类或者ClassLoader来返回InputStream。而之前的分析可知，当loadBeanDefinition时，最终应用的是InputSource inputSource = new InputSource(inputStream);InputSource，属于org.xml.sax包，是一个XML形式的输入流。

3.Context组件

Context组件在Spring的org.springframework.context包下，它的作用主要是给Spring提供一个运行时的环境，用以保证各个对象的状态。其中ApplicationContext是Context的顶级父类接口，它除了继承一个能表示应用环境的基本信息接口外，还继承了5个接口，这5个接口扩展了Context的功能。

public interface ApplicationContext extends EnvironmentCapable, ListableBeanFactory, HierarchicalBeanFactory, MessageSource, ApplicationEventPublisher, ResourcePatternResolver

可以发现其主要应用子类为ClassPathXmlApplicationContext,FileSystemXmlApplicationContext，以及应用在Web上的XmlWebApplicationContext.

二. ApplicationContext源码详解

在ApplicationContext的设计中，一方面可以看到它继承了BeanFactory接口体系结构的ListableBeanFactory, HierarchicalBeanFactory，具备了IOC容器的基本功能；另一方面，通过继承MessageSource, ApplicationEventPublisher, ResourcePatternResolver这些接口，使得其被赋予了更高级别的特性。

1.java doc

/**
 * Central interface to provide configuration for an application.
 * This is read-only while the application is running, but may be
 * reloaded if the implementation supports this.
 *
 * <p>An ApplicationContext provides:
 * <ul>
 * <li>Bean factory methods for accessing application components.
 * Inherited from {@link org.springframework.beans.factory.ListableBeanFactory}.
 * <li>The ability to load file resources in a generic fashion.
 * Inherited from the {@link org.springframework.core.io.ResourceLoader} interface.
 * <li>The ability to publish events to registered listeners.
 * Inherited from the {@link ApplicationEventPublisher} interface.
 * <li>The ability to resolve messages, supporting internationalization.
 * Inherited from the {@link MessageSource} interface.
 * <li>Inheritance from a parent context. Definitions in a descendant context
 * will always take priority. This means, for example, that a single parent
 * context can be used by an entire web application, while each servlet has
 * its own child context that is independent of that of any other servlet.
 * </ul>
 *
 * <p>In addition to standard {@link org.springframework.beans.factory.BeanFactory}
 * lifecycle capabilities, ApplicationContext implementations detect and invoke
 * {@link ApplicationContextAware} beans as well as {@link ResourceLoaderAware},
 * {@link ApplicationEventPublisherAware} and {@link MessageSourceAware} beans.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see ConfigurableApplicationContext
 * @see org.springframework.beans.factory.BeanFactory
 * @see org.springframework.core.io.ResourceLoader
 */

ApplicationContext添加的功能主要表现在 ：

1)可以支持不同的信息源，它扩展了MessageSource,支持国际化。

2)访问资源,主要就是ResourceLoader的继承，这样可以从不同地方得到bean定义的资源。

3)支持应用事件，继承了ApplicationEventPublisher, 这样在上下文中引入了事件机制。

2.源码

public interface ApplicationContext extends EnvironmentCapable, ListableBeanFactory, HierarchicalBeanFactory,
        MessageSource, ApplicationEventPublisher, ResourcePatternResolver {

    /**
     * Return the unique id of this application context.
     * @return the unique id of the context, or {@code null} if none
     *///返回标志Context的Id编号
    String getId();

    /**
     * Return a name for the deployed application that this context belongs to.
     * @return a name for the deployed application, or the empty String by default
     */
                //返回context所属应用名称
    String getApplicationName();

    /**
     * Return a friendly name for this context.
     * @return a display name for this context (never {@code null})
     */
    String getDisplayName();

    /**
     * Return the timestamp when this context was first loaded.
     * @return the timestamp (ms) when this context was first loaded
     */
                //返回loaded时间戳
    long getStartupDate();

    /**
     * Return the parent context, or {@code null} if there is no parent
     * and this is the root of the context hierarchy.
     * @return the parent context, or {@code null} if there is no parent
     */
               //返回双亲ApplicationContext，证明这里是有层次关系的
    ApplicationContext getParent();

    /**
     * Expose AutowireCapableBeanFactory functionality for this context.
     * <p>This is not typically used by application code, except for the purpose of
     * initializing bean instances that live outside of the application context,
     * applying the Spring bean lifecycle (fully or partly) to them.
     * <p>Alternatively, the internal BeanFactory exposed by the
     * {@link ConfigurableApplicationContext} interface offers access to the
     * {@link AutowireCapableBeanFactory} interface too. The present method mainly
     * serves as a convenient, specific facility on the ApplicationContext interface.
     * <p><b>NOTE: As of 4.2, this method will consistently throw IllegalStateException
     * after the application context has been closed.</b> In current Spring Framework
     * versions, only refreshable application contexts behave that way; as of 4.2,
     * all application context implementations will be required to comply.
     * @return the AutowireCapableBeanFactory for this context
     * @throws IllegalStateException if the context does not support the
     * {@link AutowireCapableBeanFactory} interface, or does not hold an
     * autowire-capable bean factory yet (e.g. if {@code refresh()} has
     * never been called), or if the context has been closed already
     * @see ConfigurableApplicationContext#refresh()
     * @see ConfigurableApplicationContext#getBeanFactory()
     */
    AutowireCapableBeanFactory getAutowireCapableBeanFactory() throws IllegalStateException;

}

3.*****单步调试ApplicationContext****

仍然采用上一节所使用的例子

ApplicationContext appContext=new ClassPathXmlApplicationContext("beans.xml");
Performer performer=(Performer) appContext.getBean("dancer");
performer.perform();

（1）ApplicationContext appContext=new ClassPathXmlApplicationContext("beans.xml");

调用构造器

/**
     * 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);
    }

可以看到除了load xml定义文件外，还有自动刷新的作用。

第二个boolean参数，是refresh启动参数。

/**
     * 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();
        }
    }

super(parent),通过逐层向上，最后会到AbstractApplicationContext.

回到上面可以看到refresh()方法即为IOC容器初始化的方法，标志着IOC容器的启动。

setConfigLocations(configLocations),设置资源属性数组

/**
     * 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;
        }
    }

(2)refresh()

该方法属于AbstractApplicationContext,即第一个抽象类。

public void refresh() throws BeansException, IllegalStateException {
        synchronized (this.startupShutdownMonitor) {
            // Prepare this context for refreshing.
            //调用容器准备刷新的方法，获取容器的当时时间，同时给容器设置同步标识 ,log信息也是源自于这个方法
            prepareRefresh();

            // Tell the subclass to refresh the internal bean factory.
            ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

            // Prepare the bean factory for use in this context.
            prepareBeanFactory(beanFactory);

            try {
                // Allows post-processing of the bean factory in context subclasses.
                postProcessBeanFactory(beanFactory);

                // Invoke factory processors registered as beans in the context.
                invokeBeanFactoryPostProcessors(beanFactory);

                // Register bean processors that intercept bean creation.
                registerBeanPostProcessors(beanFactory);

                // Initialize message source for this context.
                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();

                // Instantiate all remaining (non-lazy-init) singletons.
                finishBeanFactoryInitialization(beanFactory);

                // Last step: publish corresponding event.
                finishRefresh();
            }

            catch (BeansException ex) {
                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;
            }
        }
    }

2.1    prepareRefresh();

为刷新Context前做准备，设定启动时间，同时Log信息同样源自这个方法。

/**
     * 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.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();
    }

2.2ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

刷新所有的BeanFactory子容器,同时这里涉及到了解析和载入BeanDefinition的步骤。

下面就分析一下BeanFactory的刷新方法refreshBeanFactory()

这里应用了委派模式，因为refreshBeanFactory（）方法属于其子类AbstractRefreshApplicationContext.

/**
     * 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());

//对IoC容器进行定制化，如设置启动参数，开启注解的自动装配等

            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);
        }
    }

1.这里可以看到一个构建DefaultListableBeanFactory容器的过程，先是构造BeanFactory,createBeanFactory()。

2.loadBeanDefinitions(beanFactory),这里载入了beanDefinition。

接下来再深入loadBeanDefinition(beanFactory)方法

该方法属于AbstractXmlApplicationContext，又是一个委派模式，让子类来实现。

/**
     * 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);
    }

1.XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory); 这个与(一)中分析的过程一样，同样是创建了一个可以载入BeanDefinition的读写器，同样用DefaultListableBeanFactory作为构造器参数，从而赋予registy属性。

2.调用loadBeanDefinitions()

/**
     * 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);
        }
    }

最终调用reader.loadBeanDefinitions(configLocations);这就又回到了（一）IOC容器初始化的过程。

到这里就完成了BeanDefinition的载入，注册工作。并且最终返回了DefaultListableBeanFactory,所以BeanDefinition持有容器依然是DefaultListableBeanFactory.所以接下来的工作就应该是实例化工作。

2.3  prepareBeanFactory(beanFactory);

这是在实例化之前进行的工作。

创建好beanFactory后，添加Spring本身需要的工具类。为容器配备了ClassLoader，PropertyEditor和BeanPostProcessor.

/**
     * 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());
        beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
        beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));

        // Configure the bean factory with context callbacks.
        beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
    //.......
    }

这里可以看到，ApplicationContextAwareProcessor作为BeanPostProcessor的实现，在这里添加。

其主要作用是当Bean实现了ApplicationContextAware接口后，当该Bean完成实例化依赖注入之后，会通过BeanPostProcessor的方式来给该Bean注入当前的ApplicationContext.从而使得该实例有能力获得ApplicationContext.

2.4 postProcessBeanFactory(beanFactory);

这个方法是预留方法，是用来对BeanFactory进行后处理的方法。

2.5 invokeBeanFactoryPostProcessors(beanFactory);

调用所有注册的BeanFactoryPostProcessor的Bean，这里也是针对BeanFactory的后置处理器的调用。

2.6 registerBeanPostProcessors(beanFactory);

BeanPostProcessor是Bean后置处理器，用于监听容器触发的事件，Bean的后置处理器。Register bean processors that intercept bean creation.这个注册主要是绑定到DefaultListableBeanFactory中取。

后置处理器向容器注册以后，容器中管理的Bean就具备了接收IoC容器事件回调的能力。

BeanPostProcessor是一个接口类，主要有两个方法，一个是postProcessBeforeInitialization，在Bean的初始化前提供回调入口；另一个是postProcessAfterInitialization，在Bean的初始化后提供回调入口。实际上，这两个后置处理器方法是一前一后围绕着Bean定义的init-method方法调用的，都是发生在populateBean()方法之后，即完成依赖注入之后发生的。

上面其实涉及到了两个Spring的扩展点，一个是BeanFactoryPostProcessor和BeanPostProcessor,他们分别在构建BeanFactory和构建Bean对象时调用，还有就是InitializationBean和DisposableBean，他们分别在Bean实例创建和销毁时被调用。

2.7   initMessageSource()和 initApplicationEventMulticaster();

初始化信息源和事件传播器。

这是由于ApplicationContext分别实现了MessageSource, ApplicationEventPublisher两个接口。

2.8 finishBeanFactoryInitialization(beanFactory)

完成BeanFactory的初始化工作，这里涉及到了对于lazy-init属性的处理。

/**
     * Finish the initialization of this context's bean factory,
     * initializing all remaining singleton beans.
     */
    protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
        // Initialize conversion service for this context.
        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));
        }

        // 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);

        // Allow for caching all bean definition metadata, not expecting further changes.
        beanFactory.freezeConfiguration();

        // Instantiate all remaining (non-lazy-init) singletons.
        beanFactory.preInstantiateSingletons();
    }

最后一个方法preInstantiateSingletons()，看注释可知实例化所有的单例，non-lazy-init，即lazy-init属性为false，而由于其默认属性就是false，所以这里会实例化所有的单例。

@Override
    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) {
            RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
            if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
                if (isFactoryBean(beanName)) {
                    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 {
                    getBean(beanName);
                }
            }
        }

        // Trigger post-initialization callback for all applicable beans...
        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();
                }
            }
        }
    }

if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit())，从这句代码可以看出当BeanDefinition不是抽象类，是单例类，lazyinit属性为false时，则预实例化，其不为FactoryBean时调用getBean()方法。

其BeanDefinition定义如下：Root bean: class [com.wly.source.spring_scoure_inspect.Dancer]; scope=singleton; abstract=false; lazyInit=false; autowireMode=0; dependencyCheck=0; autowireCandidate=true; primary=false; factoryBeanName=null; factoryMethodName=null; initMethodName=null; destroyMethodName=null; defined in class path resource [beans.xml]

所以这里就完成了预实例化的过程。

2.9 finishRefresh()

初始化容器的生命周期事件处理器，并发布容器的生命周期事件。

/**
     * Finish the refresh of this context, invoking the LifecycleProcessor's
     * onRefresh() method and publishing the
     * {@link org.springframework.context.event.ContextRefreshedEvent}.
     */
    protected void finishRefresh() {
        // Initialize lifecycle processor for this context.
        initLifecycleProcessor();

        // Propagate refresh to lifecycle processor first.
        getLifecycleProcessor().onRefresh();

        // Publish the final event.
        publishEvent(new ContextRefreshedEvent(this));

        // Participate in LiveBeansView MBean, if active.
        LiveBeansView.registerApplicationContext(this);
    }