这个方法应该是ApplicationContext刷新的时候，最重要的方法了，因为所有的bean，如果不是lazy-init的都会在这一步进行实例化，并且做一些处理。
狭义上的Bean生命周期就在这一步进行完成，我们一起看看
//结束context的bean Factory实例化，然后实例化所有的非懒加载单例。
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.
// 初始化上下文的转换服务，ConversionService是一个类型转换接口
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.
// 初始化LoadTimeWeaverAware Bean
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
// 停止使用临时的类加载器
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
//缓存所有的bean definition数据，不期望以后会改变
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
// 实例化所有的non-lazy-init 单例
beanFactory.preInstantiateSingletons();
}
分析
- ConversionService是一个服务接口用于类型转换，这也是转换系统的入口点。 这一步没有做什么处理
// 如果有ConversionService的Bean，就设置
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));
}
- 先获取实现了LoadTimeWeaverAware接口的bean名称，LoadTimeWeaverAware是类加载时织入的意思。getBean则是让实现LoadTimeWeaverAware的对象提前实例化。
// 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);
}
- 冻结之前beandifinition的配置，留作后面的缓存用
beanFactory.freezeConfiguration();
public void freezeConfiguration() {
this.configurationFrozen = true;
this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
}
- 实例化所有的non-lazy-init单例，bean真正实例化的时刻到了
基本逻辑，首先获取beanDefinitionNames，查看对应beanName的是否是FactoryBean，不管是不是，最后都要执行getBean方法，getBean方法内部做了实例化Bean的操作。
实例化单例Bean之后，如果Bean实现了SmartInitializingSingleton,就执行afterSingletonsInstantiated方法。
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.
// 首先将bean difinition赋值到一个新的集合中。
List<String> beanNames = new ArrayList<String>(this.beanDefinitionNames);
// Trigger initialization of all non-lazy singleton beans...
// 出发单例的实例化
for (String beanName : beanNames) {
RootBeanDefinition bd = getMergedLocalBeanDefinition(beanName);
// 不是abstract,不是lazy-init，但是是singleton的才执行如下
if (!bd.isAbstract() && bd.isSingleton() && !bd.isLazyInit()) {
//是否为FactoryBean,不是的话直接getBean(beanName)，也就是实例化
// 如果是FactoryBean，判断FactoryBean有没有额外的配置
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...
// 触发所有应用Bean的post-initialization 回调
for (String beanName : beanNames) {
//获取Bean的实例
Object singletonInstance = getSingleton(beanName);
// 如果实例实现了SmartInitializingSingleton，执行afterSingletonsInstantiated方法。
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();
}
}
}
}
最后
Bean的实例化大流程，现在我们已经有了概念，下次一起看bean实例化的真正细节。
