最近有幸接触了spring源码模块，正在做spring的源码翻译工作:简单从说一下 bean生命周期
顺便感谢领我入门的书，人，视频教程
关注下方的核心代码:
populateBean(beanName, mbd, instanceWrapper);
// 初始化bean对象
exposedObject = initializeBean(beanName, exposedObject, mbd);
这段spring代码也就是说明了spring是怎么创建bean后,注入值,回调各种回调接口
AUTOWIRE -> PostConstruct | aware-> BPPbefore -> afterPer-> init-method-> BPPafter
以 AnnotationConfigApplicationContext为例按照源码调用链执行讲解
第一步创建容器看refresh方法
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
// 创建reader scanner beanfactory 注入七个PostProcessor
this();
// 注册配置类到BeanDefinition
register(annotatedClasses);
// 启动容器
refresh();
}第二步看实例化单例的方法finishBeanFactoryInitialization
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
// 获取beanfactory 也就是DefaultListableBeanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
// 2个beanPostProcesserr
prepareBeanFactory(beanFactory);
try {
// 暂无实现,但是允许程序员继承后处理postProcessBeanFactory
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// 注册BeanFactoryPostProcessors并且完成bean和Import等的解析【ConfigurationClassPostProcessor】
// Invoke factory processors registered as beans in the context.
// BeanFactoryPostProcessors核心处理 同时处理一个beanPostProcesserr
/**
* 这里有一个非常核心的类
* ConfigurationClassPostProcessor[BeanDefinitionRegistryPostProcessor]用来加载configuration component componentscan import importSelector等核心IOC过程
*/
invokeBeanFactoryPostProcessors(beanFactory);
//
// Register bean processors that intercept bean creation.
// 四个beanPostProcesserr 这些beanPostProcesserr 被建立成一个数组，放置在
// private final List<BeanPostProcessor> beanPostProcessors = new CopyOnWriteArrayList<>();
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
// 初始化messagesource
initMessageSource();
// Initialize event multicaster for this context.
// 初始化 事件广播
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
// 暂无实现，可以自定义上下文用于扩展
onRefresh();
// Check for listener beans and register them.
// 注册相关监听器
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
// 创建BEAN实例，注意这里不处理原型bean,懒加载的bean等
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
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;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
}
}
}
在finishBeanFactoryInitialization时候看加载饥饿单例
// 饥饿加载所有的单例bean
beanFactory.preInstantiateSingletons();内部的
if (isEagerInit) {
// 默认是饥饿加载
getBean(beanName);
}
沿着调用链向下看第一个AbstractBeanFactory核心方法getSingleton的【 return createBean(beanName, mbd, args);】
其实现交给AbstractAutowireCapableBeanFactory
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, () -> {
try {
// 单列bean的创建
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
// Explicitly remove instance from singleton cache: It might have been put there
// eagerly by the creation process, to allow for circular reference resolution.
// Also remove any beans that received a temporary reference to the bean.
destroySingleton(beanName);
throw ex;
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}========================================接下来就是核心=======================================
上面的代码只是链路的调用;不用关注具体
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final @Nullable Object[] args)
throws BeanCreationException {
/**
* 有不同的方式创建bean
*
* 1 工厂创建
* 2 构造注入
* 3无参创建
*/
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);
}
if (instanceWrapper == null) {
instanceWrapper = createBeanInstance(beanName, mbd, args);
}
final Object bean = instanceWrapper.getWrappedInstance();
Class<?> beanType = instanceWrapper.getWrappedClass();
if (beanType != NullBean.class) {
mbd.resolvedTargetType = beanType;
}
// Allow post-processors to modify the merged bean definition.
synchronized (mbd.postProcessingLock) {
if (!mbd.postProcessed) {
try {
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
}
catch (Throwable ex) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Post-processing of merged bean definition failed", ex);
}
mbd.postProcessed = true;
}
}
// Eagerly cache singletons to be able to resolve circular references
// even when triggered by lifecycle interfaces like BeanFactoryAware.
boolean earlySingletonExposure = (mbd.isSingleton() && this.allowCircularReferences &&
isSingletonCurrentlyInCreation(beanName));
if (earlySingletonExposure) {
if (logger.isDebugEnabled()) {
logger.debug("Eagerly caching bean '" + beanName +
"' to allow for resolving potential circular references");
}
//
addSingletonFactory(beanName, () -> getEarlyBeanReference(beanName, mbd, bean));
}
// Initialize the bean instance.
Object exposedObject = bean;
///这里就是APAI的原因/
///autowired postConstructor AfterP init-method//
try {
// 设置对象的属性 AUTOWIRE 处理PostConstruct
// autowired -> postConstruct
populateBean(beanName, mbd, instanceWrapper);
// 初始化bean对象 aware-> before -> afterPer-> init-method-> after
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
catch (Throwable ex) {
if (ex instanceof BeanCreationException && beanName.equals(((BeanCreationException) ex).getBeanName())) {
throw (BeanCreationException) ex;
}
else {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Initialization of bean failed", ex);
}
}
if (earlySingletonExposure) {
Object earlySingletonReference = getSingleton(beanName, false);
if (earlySingletonReference != null) {
if (exposedObject == bean) {
exposedObject = earlySingletonReference;
}
else if (!this.allowRawInjectionDespiteWrapping && hasDependentBean(beanName)) {
String[] dependentBeans = getDependentBeans(beanName);
Set<String> actualDependentBeans = new LinkedHashSet<>(dependentBeans.length);
for (String dependentBean : dependentBeans) {
if (!removeSingletonIfCreatedForTypeCheckOnly(dependentBean)) {
actualDependentBeans.add(dependentBean);
}
}
if (!actualDependentBeans.isEmpty()) {
throw new BeanCurrentlyInCreationException(beanName,
"Bean with name '" + beanName + "' has been injected into other beans [" +
StringUtils.collectionToCommaDelimitedString(actualDependentBeans) +
"] in its raw version as part of a circular reference, but has eventually been " +
"wrapped. This means that said other beans do not use the final version of the " +
"bean. This is often the result of over-eager type matching - consider using " +
"'getBeanNamesOfType' with the 'allowEagerInit' flag turned off, for example.");
}
}
}
}
// Register bean as disposable.
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
}
catch (BeanDefinitionValidationException ex) {
throw new BeanCreationException(
mbd.getResourceDescription(), beanName, "Invalid destruction signature", ex);
}
return exposedObject;
}
//autowired -> postConstruct
populateBean(beanName, mbd, instanceWrapper);
// 初始化bean对象 aware-> before -> afterPer-> init-method-> after
exposedObject = initializeBean(beanName, exposedObject, mbd);
这两段方法处理了各个生命周期的创建赋值
1 populateBean 方法如下
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
/**
* AutowiredAnnotationBeanPostProcessor 處理@Autowired
* CommonAnnotationBeanPostProcessor 負責@Resource @PostConstruct @PreDestroy(交給父类和本身处理)
*/
InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
return;
}
}
}
}
这里也就是说明了@Autowired -》 @PostConstruct
2
protected Object initializeBean(final String beanName, final Object bean, @Nullable RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged((PrivilegedAction<Object>) () -> {
invokeAwareMethods(beanName, bean);
return null;
}, getAccessControlContext());
}
else {
// 什么是Aware spring的尿性是说我定义了一部分的Aware注入，当实现指定Aware接口，spring会将属于IOC容器内部的一些组件比如applicationContext等通过set方法赋值
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
// PostProcessorsBefore BeanPostProcessors的前置处理
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// InitializingBean afterPropertiesSet(); init-Method;
// 这里调用afterPropertiesSet 以及bean 的 init-method
invokeInitMethods(beanName, wrappedBean, mbd);
}
catch (Throwable ex) {
throw new BeanCreationException(
(mbd != null ? mbd.getResourceDescription() : null),
beanName, "Invocation of init method failed", ex);
}
if (mbd == null || !mbd.isSynthetic()) {
// BeanPostProcessorsAfter BeanPostProcessors的后置处理
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
最终也就是说:
// 设置对象的属性 AUTOWIRE 处理PostConstruct
// autowired -> postConstruct
populateBean(beanName, mbd, instanceWrapper);
// 初始化bean对象 aware-> before -> afterPer-> init-method-> after
exposedObject = initializeBean(beanName, exposedObject, mbd);
最后的destory这里不说
