spring源码学习笔记-初始化（六）-完成及异常处理

转自http://www.sandzhang.com/blog/2011/04/08/spring-study-notes-initialization-6/

refresh()方法中在上篇看完了MessageSource及时间监听器等初始话处理，这篇继续往下看。

注：refresh()的代码就不再次列举了，请看spring源码中AbstractApplicationContext类。

一、finishBeanFactoryInitialization(beanFactory)这个方法将完成BeanFactory的初始化，主要做的事就是初始化除了之前处理过的特殊bean之外的所有单例bean，代码如下：

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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)); } beanFactory.setTempClassLoader(null); beanFactory.freezeConfiguration(); beanFactory.preInstantiateSingletons();

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));
}

beanFactory.setTempClassLoader(null);
beanFactory.freezeConfiguration();
beanFactory.preInstantiateSingletons();

第1-5行判断如果定义了名为conversionService并且类型为ConversionService的bean，则把其设置为beanFactory的conversionService属性。这个主要是用来提供数据转化服务的
销毁之前在prepareBeanFactory()中生成的临时ClassLoader
freezeConfiguration()的代码如下：

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this.configurationFrozen = true; synchronized (this.beanDefinitionMap) { this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames); }

this.configurationFrozen = true;
synchronized (this.beanDefinitionMap) {
this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
}

这个方法就是代表bean定义等配置已经可以缓存了，不会再有其他地方对其做修改了
最后一行就是对所有非延迟加载的单例bean进行初始化了我们来看下这个方法的代码：

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if (this.logger.isInfoEnabled()) {
this.logger.info("Pre-instantiating singletons in " + this);
}
synchronized (this.beanDefinitionMap) {
for (String beanName : this.beanDefinitionNames) {
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>() {
public Boolean run() {
return ((SmartFactoryBean) factory).isEagerInit();
}
}, getAccessControlContext());
}
else {
isEagerInit = factory instanceof SmartFactoryBean && ((SmartFactoryBean) factory).isEagerInit();
}
if (isEagerInit) {
getBean(beanName);
}
}
else {
getBean(beanName);
}
}
}
}

if (this.logger.isInfoEnabled()) {
this.logger.info("Pre-instantiating singletons in " + this);
}
synchronized (this.beanDefinitionMap) {
for (String beanName : this.beanDefinitionNames) {
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>() {
public Boolean run() {
return ((SmartFactoryBean) factory).isEagerInit();
}
}, getAccessControlContext());
}
else {
isEagerInit = factory instanceof SmartFactoryBean && ((SmartFactoryBean) factory).isEagerInit();
}
if (isEagerInit) {
getBean(beanName);
}
}
else {
getBean(beanName);
}
}
}
}

首先是一行info级别的日志，然后在对象beanDefinitionMap的同步下循环所有bean的name分别进行初始化

首先获取bean定义信息对象bd，然后进行判断，这里只对非抽象bean（抽象bean是用于继承定义配置等信息的不可初始化）、单例、非延迟加载的bean进行处理

判断如果是FactoryBean则进行下面的处理，如果不是直接调用getBean(beanName)，这个方法调用会进行这个bean的初始化，关于这个方法还是放到BeanFactory的单独分析里面这里就不往里看了。

对于FactoryBean的获取，要在beanname前加上一个&，然后会先判断是否是SmartFactoryBean并且渴望初始化（EagerInit），如果是才调用getBean(beanName)，否则这个应该是在第一次调用工厂的getObject的时候才初始化

注：对于这中间AccessController.doPrivileged的运用没有搞明白，留待以后分析，不知道为什么要在这里使用这个

二、最后的一个处理是finishRefresh()方法，代码如下：

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initLifecycleProcessor(); getLifecycleProcessor().onRefresh(); publishEvent(new ContextRefreshedEvent(this));

initLifecycleProcessor();
getLifecycleProcessor().onRefresh();
publishEvent(new ContextRefreshedEvent(this));

1.先看initLifecycleProcessor()方法的代码：

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ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {
this.lifecycleProcessor =
beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);
if (logger.isDebugEnabled()) {
logger.debug("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");
}
}
else {
DefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();
defaultProcessor.setBeanFactory(beanFactory);
this.lifecycleProcessor = defaultProcessor;
beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate LifecycleProcessor with name '" +
LIFECYCLE_PROCESSOR_BEAN_NAME +
"': using default [" + this.lifecycleProcessor + "]");
}
}

ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(LIFECYCLE_PROCESSOR_BEAN_NAME)) {
this.lifecycleProcessor =
beanFactory.getBean(LIFECYCLE_PROCESSOR_BEAN_NAME, LifecycleProcessor.class);
if (logger.isDebugEnabled()) {
logger.debug("Using LifecycleProcessor [" + this.lifecycleProcessor + "]");
}
}
else {
DefaultLifecycleProcessor defaultProcessor = new DefaultLifecycleProcessor();
defaultProcessor.setBeanFactory(beanFactory);
this.lifecycleProcessor = defaultProcessor;
beanFactory.registerSingleton(LIFECYCLE_PROCESSOR_BEAN_NAME, this.lifecycleProcessor);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate LifecycleProcessor with name '" +
LIFECYCLE_PROCESSOR_BEAN_NAME +
"': using default [" + this.lifecycleProcessor + "]");
}
}

这个方法主要是用来初始化生命周期管理器LifecycleProcessor的

如果用户定义了名为lifecycleProcessor类型为LifecycleProcessor的LocalBean，则赋值给当前ApplicationContext的lifecycleProcessor属性
如果用户没有定义，则初始化默认的生命周期管理器DefaultLifecycleProcessor，注册单例bean，并赋值给lifecycleProcessor属性

2.initLifecycleProcessor()方法之后则是对生命周期管理器的触发，LifecycleProcessor有两个触发点onRefresh()和onClose()，当前正处于refresh所以调用其onRefresh()方法

3.调用publishEvent()方法发布ContextRefreshedEvent事件，[b]publishEvent()的代码也很简单就不介绍了，就是调用当前上下文及parent的ApplicationEventMulticaster的multicastEvent()方法，这个放到分析事件处理模块时再去详细分析。[/b]

三、最后分析一下在整个try代码块中如果抛出异常的处理，可以看到分为了两个方法调用：

1.destroyBeans()代码很简单，就是调用BeanFactory的destroySingletons()方法销毁所有单例bean。还是暂不细看放到BeanFactory专项分析里去

2.cancelRefresh()这个方法代码看一下：

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synchronized (this.activeMonitor) { this.active = false; }

synchronized (this.activeMonitor) {
this.active = false;
}

就是在同步下设置状态值而已，但是有个小细节，这个方法在AbstractRefreshableApplicationContext和GenericApplicationContext两个子类中进行了重写，但是也很简单，就是增加了一个beanFactory.setSerializationId(null)然后依旧调用上面super中的方法进行修改状态

关于ApplicationContext的基本初始化的过车这就分析完了，中间碰到了很多问题，也还有很多地方需要详细研究，下面列举备忘一下，后面挨个分析：

bean定义的加载
bean的初始化
BeanFactory的一些核心方法
BeanFactory和ApplictionContext的关系以及各自的类继承框架
扩展点BeanFactoryPostProcessor及BeanPostProcessor
事件监听器ApplicationListener
信息管理器MessageSource
属性编辑器PropertyEditor
生命周期管理器LifecycleProcessor
还有几个小细节例如LoadTimeWeaver、MergedBeanDefinitionPostProcessor、AccessController.doPrivileged等