ApplicationContext（九）初始化非延迟的 bean
此至，ApplicationContext 已经完成了全部的准备工作，开始初始化剩余的 bean 了(第 11 步)。
public void refresh() throws BeansException, IllegalStateException {
// 11. 初始化剩余的 bean (部分在 invokeBeanFactoryPostProcessors 已经初始化)
finishBeanFactoryInitialization(beanFactory);
}
finishBeanFactoryInitialization 主要是实例化非懒加载的 bean。
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// 1. 注册 ConversionService，注意 beanName 必须为 conversionService
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);
// 2. 冻结所有的 bean 定义，说明注册的 bean 定义将不被修改
beanFactory.freezeConfiguration();
// 3. 初始化剩下的 bean
beanFactory.preInstantiateSingletons();
}
一、注册 ConversionService
(1) String2DateConverter
public class String2DateConverter implements Converter<String, Date> {
@Override
public Date convert(String source) {
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
try {
return sdf.parse(source);
} catch (ParseException e) {
;
}
return null;
}
}
(2) 注册
注意：beanName 必须为 conversionService
<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
<property name="converters">
<set>
<bean class="com.github.binarylei.spring01.day0728.conversionservice.String2DateConverter"/>
</set>
</property>
</bean>
(3) 测试
@Test
public void test() {
DefaultConversionService service = new DefaultConversionService();
service.addConverter(new String2DateConverter());
Date value = service.convert("2018-08-02", Date.class);
System.out.println(value);
}
二、冻结配置
源代码【DefaultListableBeanFactory】
public void freezeConfiguration() {
this.configurationFrozen = true;
this.frozenBeanDefinitionNames = StringUtils.toStringArray(this.beanDefinitionNames);
}
三、初始化非延迟加载
public void preInstantiateSingletons() throws BeansException {
if (this.logger.isDebugEnabled()) {
this.logger.debug("Pre-instantiating singletons in " + this);
}
// 1. 创建剩下的单实例 bean
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);
}
}
}
// 2. 筛选出实现了 SmartInitializingSingleton 接口的 bean，回调 afterSingletonsInstantiated() 方法
// @EventListener 注解的方式注册监听器就是在这一步完成的
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();
}
}
}
}
每天用心记录一点点。内容也许不重要，但习惯很重要！