摘要: 本文结合《Spring源码深度解析》来分析Spring 5.0.6版本的源代码。若有描述错误之处，欢迎指正。
完成BeanFactory的初始化工作，其中包括ConversionService的设置、配置冻结以及非延迟加载的bean的初始化工作。
/**
* 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));
} // 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(strVal -> 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); // Allow for caching all bean definition metadata, not expecting further changes.
// 冻结所有的bean定义，说明注册的bean定义将不被修改或任何进一步的处理
beanFactory.freezeConfiguration(); // Instantiate all remaining (non-lazy-init) singletons.
// 初始化剩下的但实例（非惰性的）
beanFactory.preInstantiateSingletons();
}
一、ConversionService的设置
之前我们提到过使用自定义类型转换器从String转换为Date的方式，那么在Spring中还提供了另一种转换方式：使用Converter。同样，我们使用一个简单的示例来了解下Converter的使用方式。
（1）定义转换器。
public class String2DateConverter implements Converter<String, Date> {
@Nullable
@Override
public Date convert(String source) {
try {
return DateUtils.parseDate(source, new String[] {"yyyy-MM-dd HH:mm:ss"});
} catch (ParseException e) {
return null;
}
}
}
（2）注册。
<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<list>
<bean class="org.cellphone.uc.String2DateConverter"/>
</list>
</property>
</bean>
（3）测试。
public class UserManager {
private Date dateValue;
public Date getDateValue() {
return dateValue;
}
public void setDateValue(Date dateValue) {
this.dateValue = dateValue;
}
@Override
public String toString() {
return "dataValue: " + dateValue;
}
}
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring/beans-test.xml");
UserManager manager = (UserManager) context.getBean("userManager");
System.out.println(manager);
}
通过以上的功能我们看到了Converter以及ConversionService提供的便利功能，其中的配置就是在当前函数中被初始化的。
二、冻结配置
冻结所有的bean定义，说明注册的bean定义将不被修改或进行任何进一步的处理。
@Override
public void freezeConfiguration() {
this.configurationFrozen = true;
this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
}
三、初始化非延迟加载
ApplicationContext实现的默认行为就是在启动时将所有单例bean提前进行实例化。提前实例化意味者作为初始化过程的一部分，ApplicationContext实例会创建并配置所有的单例bean。通常情况下这是一件好事，因为这样在配置中的任何错误就会即刻被发现（否则的话可能要花几个小时甚至几天）。而这个实例的过程就是在finishBeanFactoryInitialization中完成的。
@Override
public void preInstantiateSingletons() throws BeansException {
if (logger.isDebugEnabled()) {
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<>(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)) {
Object bean = getBean(FACTORY_BEAN_PREFIX + beanName);
if (bean instanceof FactoryBean) {
final FactoryBean<?> factory = (FactoryBean<?>) bean;
boolean isEagerInit;
if (System.getSecurityManager() != null && factory instanceof SmartFactoryBean) {
isEagerInit = AccessController.doPrivileged((PrivilegedAction<Boolean>)
((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((PrivilegedAction<Object>) () -> {
smartSingleton.afterSingletonsInstantiated();
return null;
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}