Spring中IOC容器的整体创建过程（源码解析）
Spring中IOC容器的整体创建过程（源码解析）
- 内容
- 一、Spring创建IOC容器源码解析配置
- 二、IOC容器创建整体流程
- 三、IOC容器创建流程分步解
-
- 由于此处源码过多，只给出大体过程，不会都贴上源码，有需要的可以自行进行debug作为参照
- 总结
内容
记录下Spring中IOC创建的整体流程一、Spring创建IOC容器源码解析配置
1.要了解Spring的源码运行流程，先从总体框架入手，并且加上debug调试完成 2.定义一个配置文件类，再加上一个测试类，然后debug启动，所有开发都在idea中完成配置文件类
@Configuration
@EnableAspectJAutoProxy
public class SpringAopConfig
{
@Bean
public MathCalculator mathCalculator()
{
return new MathCalculator();
}
@Bean
public LogAspects logAspects()
{
return new LogAspects();
}
}
测试类
@Test
public void aopTest01()
{
//断点可加在这一行，然后进行debug运行
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(SpringAopConfig.class);
MathCalculator bean = applicationContext.getBean(MathCalculator.class);
System.out.println(bean.div(1, 2));
}
二、IOC容器创建整体流程
进入调试后得到以下代码，重点关注 refresh() 方法
public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
this();
register(annotatedClasses);
refresh();
}
跳进**refresh()**方法，发现整个IOC容器的整体流程如下：
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//1.刷新前的预处理
prepareRefresh()
//2.获取BeanFactory
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory()
//3.BeanFactory的预准备工作（即设置BeanFactory的一些属性）
prepareBeanFactory(beanFactory)
try {
//4.BeanFactory准备工作完成后进行的后置处理操作
postProcessBeanFactory(beanFactory)
============以上都是关于BeanFactory的创建及预准备工作==============
//5.执行BeanFactoryPostProcessors（即后置处理器）
invokeBeanFactoryPostProcessors(beanFactory)
//6.注册BeanPostProcessors
//注：此处是bean的后置处理器，上面是BeanFactory的后置处理器
registerBeanPostProcessors(beanFactory)
//7.初始化MessageSource组件（用于国际化功能、消息绑定、消息解析等）
initMessageSource()
//8.初始化事件派发器
initApplicationEventMulticaster()
//9.用于子类重写该方法，可以在容器刷新的时候自定义逻辑
onRefresh()
//10.注册所有的ApplicationListener组件
registerListeners()
//11.最重要的一步：初始化所有剩下的单实例bean
finishBeanFactoryInitialization(beanFactory)
//12.完成BeanFactory的初始化创建工作，至此IOC容器创建完成
finishRefresh();
}
上面分析了IOC容器创建的整体流程，接下来对每一步进行详细的解析
三、IOC容器创建流程分步解
由于此处源码过多，只给出大体过程，不会都贴上源码，有需要的可以自行进行debug作为参照
1.prepareRefresh()
刷新前的预处理
@Override
protected void prepareRefresh() {
this.scanner.clearCache();
super.prepareRefresh();
}
此步主要完成以下功能：
- initPropertySources()
初始化一些属性设置，用于子类自定义个性化的属性设置 - getEnvironment().validateRequiredProperties();
检验自定义属性的合法性 - this.earlyApplicationEvents = new LinkedHashSet();
保存IOC容器中的一些早期的事件
2.obtainFreshBeanFactory()
获取BeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
- refreshBeanFactory()；
创建了一个默认的BeanFactory并设置了一个序列化ID，然后将其保存至IOC容器中，由于后续获取 - getBeanFactory();
获取刚刚创建的BeanFactory对象 - return beanFactory;
将刚刚获取的BeanFactory对象返回
3.prepareBeanFactory(beanFactory)
BeanFactory的预准备工作
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
此步主要完成以下功能：
- 设置BeanFactory的类加载器，支持表达式解析器等…
- 添加部分BeanPostProcessor
- 设置忽略的自动装配的接口，例如EnvironmentAware、EmbeddedValueResolverAware、xxx等
- 注册可以解析的自动装配组件，从而我们可以直接在任何组件中注入这些自动装配组件（BeanFactory、ApplicationContext、xxx等）
- 添加编译时的AspectJ
- 给BeanFactory中注册一些能用的组件
environment【StandardEnvironment】
systemProperties【Map
4.postProcessBeanFactory(beanFactory)
BeanFactory准备工作完成后进行的后置处理工作（留给子类进行重写）
以上4步都是关于BeanFactory的创建、准备、初始化工作
5.**invokeBeanFactoryPostProcessors(beanFactory)**
执行BeanFactoryPostProcessor，即BeanFactory的后置处理器，在BeanFactory标准初始化之后执行的
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<String>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new LinkedList<BeanFactoryPostProcessor>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new LinkedList<BeanDefinitionRegistryPostProcessor>();
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanFactoryPostProcessor>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
此处有两个接口BeanFactoryPostProcessor和 BeanDefinitionRegistryPostProcessor，两个接口的方法依次执行
- 先执行BeanDefinitionRegistryPostProcessor的方法
- 1）获取所有的BeanDefinitionRegistryPostProcessor
- 2）先执行实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor中的方法，调用BeanDefinitionRegistryPostProcessor.postProcessBeanDefinitionRegistry(registry);
- 3）再执行实现了Ordered接口的BeanDefinitionRegistryPostProcessor中的方法
- 4）最后执行没有实现任何优先级或是顺序接口的BeanDefinitionRegistryPostProcessor中的方法
- 再执行BeanFactoryPostProcessor的方法
- 1）其执行顺序如上一样，都是先查找优先级高的BeanFactoryPostProcessor，然后依次执行
6.registerBeanPostProcessors(beanFactory)
注册BeanPostProcessor(Bean的后置处理器，上面的是BeanFactory的后置处理器)，此处只是注册，还未执行
并且对于不同接口的BeanPostProcessor，其在Bean前后的执行时机也是不一样的，主要有如下BeanPostProcessor：
- BeanPostProcessor
- MergedBeanDefinitionPostProcessor
- InstantiationAwareBeanPostProcessor
- SmartInstantiationAwareBeanPostProcessor
- DestructionAwareBeanPostProcess
注册代码如下：
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
该部分主要流程如下：
1). 获取所有的BeanPostProcessor
2).先注册实现了PriortyOrdered接口的BeanPostProcessor，调用registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors)完成注册
3).再注册实现了Ordered接口的BeanPostProcesso
4).注册没有实现任何顺序接口的的BeanPostProcesso
5).最后注册MergedBeanDefinitionPostProcessor
7.initMessageSource()
初始化MessageResource组件（用于做国际化功能、消息绑定、消息解析等）
8.initApplicationEventMulticaster()
初始化事件派发器
代码如下：
protected void initApplicationEventMulticaster() {
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (beanFactory.containsLocalBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME)) {
this.applicationEventMulticaster =
beanFactory.getBean(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, ApplicationEventMulticaster.class);
if (logger.isDebugEnabled()) {
logger.debug("Using ApplicationEventMulticaster [" + this.applicationEventMulticaster + "]");
}
}
else {
this.applicationEventMulticaster = new SimpleApplicationEventMulticaster(beanFactory);
beanFactory.registerSingleton(APPLICATION_EVENT_MULTICASTER_BEAN_NAME, this.applicationEventMulticaster);
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate ApplicationEventMulticaster with name '" +
APPLICATION_EVENT_MULTICASTER_BEAN_NAME +
"': using default [" + this.applicationEventMulticaster + "]");
}
}
}
主要有以下步骤：
1). 从IOC容器中获取BeanFactory
2). 查找BeanFactory中是否有派发器ApplicationEventMulticaster，如果有则返回，如果没有进行下一步
3). 在BeanFactory中没有派发器，那么创建一个默认的派发器SimpleApplicationEventMulticaster
4). 并将这个创建的派发器注册到BeanFactory中，从而以后其它组件可以自动注入派发器
9.onRefresh()
留给子类重写该方法，用于在容器刷新时自定义逻辑
10.registerListeners()
注册监听器，将项目中所有的ApplicationListener注入到BeanFactory的派发器中
protected void registerListeners() {
// Register statically specified listeners first.
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
for (String listenerBeanName : listenerBeanNames) {
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// Publish early application events now that we finally have a multicaster...
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
主要有以下步骤：
1). 从IOC容器中拿到所有的ApplicationListener
2).将所有的ApplicationListener注入到ApplicationEventMulticaste，这样就可以完成事件驱动
3).利用派发器派发之前步骤产生的事件
11.finishBeanFactoryInitialization(beanFactory)
整个IOC容器创建中最重要的一步，初始化所有剩下的单实例bean
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.
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);
}
}
}
// 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(new PrivilegedAction<Object>() {
@Override
public Object run() {
smartSingleton.afterSingletonsInstantiated();
return null;
}
}, getAccessControlContext());
}
else {
smartSingleton.afterSingletonsInstantiated();
}
}
}
}
主要有以下步骤：
1). 获取容器中的所有bean，利用for循环依次进行初始化和创建对象，for循环中流程如下：
1.1). 先获取单个bean的定义信息RootBeanDefinition
1.2). 判断其是否抽象类、是否单实例的、是否懒加载
1.2.1). 如果满足上述条件，再判断是否为FactoryBean（如果是，则调用FactoryBean接口的getObject方法创建bean）
1.2.2). 如果不是FactoryBean，则调用getBean(beanName)创建bean
getBean方法的代码如下：
protected <T> T doGetBean(
final String name, final Class<T> requiredType, final Object[] args, boolean typeCheckOnly)
throws BeansException {
final String beanName = transformedBeanName(name);
Object bean;
// Eagerly check singleton cache for manually registered singletons.
Object sharedInstance = getSingleton(beanName);
if (sharedInstance != null && args == null) {
if (logger.isDebugEnabled()) {
if (isSingletonCurrentlyInCreation(beanName)) {
logger.debug("Returning eagerly cached instance of singleton bean '" + beanName +
"' that is not fully initialized yet - a consequence of a circular reference");
}
else {
logger.debug("Returning cached instance of singleton bean '" + beanName + "'");
}
}
bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
}
else {
// Fail if we're already creating this bean instance:
// We're assumably within a circular reference.
if (isPrototypeCurrentlyInCreation(beanName)) {
throw new BeanCurrentlyInCreationException(beanName);
}
// Check if bean definition exists in this factory.
BeanFactory parentBeanFactory = getParentBeanFactory();
if (parentBeanFactory != null && !containsBeanDefinition(beanName)) {
// Not found -> check parent.
String nameToLookup = originalBeanName(name);
if (args != null) {
// Delegation to parent with explicit args.
return (T) parentBeanFactory.getBean(nameToLookup, args);
}
else {
// No args -> delegate to standard getBean method.
return parentBeanFactory.getBean(nameToLookup, requiredType);
}
}
if (!typeCheckOnly) {
markBeanAsCreated(beanName);
}
try {
final RootBeanDefinition mbd = getMergedLocalBeanDefinition(beanName);
checkMergedBeanDefinition(mbd, beanName, args);
// Guarantee initialization of beans that the current bean depends on.
String[] dependsOn = mbd.getDependsOn();
if (dependsOn != null) {
for (String dep : dependsOn) {
if (isDependent(beanName, dep)) {
throw new BeanCreationException(mbd.getResourceDescription(), beanName,
"Circular depends-on relationship between '" + beanName + "' and '" + dep + "'");
}
registerDependentBean(dep, beanName);
getBean(dep);
}
}
// Create bean instance.
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
try {
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);
}
else if (mbd.isPrototype()) {
// It's a prototype -> create a new instance.
Object prototypeInstance = null;
try {
beforePrototypeCreation(beanName);
prototypeInstance = createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
bean = getObjectForBeanInstance(prototypeInstance, name, beanName, mbd);
}
else {
String scopeName = mbd.getScope();
final Scope scope = this.scopes.get(scopeName);
if (scope == null) {
throw new IllegalStateException("No Scope registered for scope name '" + scopeName + "'");
}
try {
Object scopedInstance = scope.get(beanName, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
beforePrototypeCreation(beanName);
try {
return createBean(beanName, mbd, args);
}
finally {
afterPrototypeCreation(beanName);
}
}
});
bean = getObjectForBeanInstance(scopedInstance, name, beanName, mbd);
}
catch (IllegalStateException ex) {
throw new BeanCreationException(beanName,
"Scope '" + scopeName + "' is not active for the current thread; consider " +
"defining a scoped proxy for this bean if you intend to refer to it from a singleton",
ex);
}
}
}
catch (BeansException ex) {
cleanupAfterBeanCreationFailure(beanName);
throw ex;
}
}
// Check if required type matches the type of the actual bean instance.
if (requiredType != null && bean != null && !requiredType.isInstance(bean)) {
try {
return getTypeConverter().convertIfNecessary(bean, requiredType);
}
catch (TypeMismatchException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Failed to convert bean '" + name + "' to required type '" +
ClassUtils.getQualifiedName(requiredType) + "'", ex);
}
throw new BeanNotOfRequiredTypeException(name, requiredType, bean.getClass());
}
}
return (T) bean;
}
对于getBean方法中代码解释如下：
- 先从缓存中获取保存的单实例bean，如果能够获取到就说明该bean之前已被创建
- 如果缓存中获取不到，那么就开始创建bean，其流程如下
- 标记当前bean已被创建
- 获取bean的定义信息 RootBeanDefinition
- 获取当前bean依赖的其它bean
- 调用createBean(beanName, mbd, args)完成bean的创建
- Object bean = resolveBeforeInstantiation(beanName, mbdToUse)，让InstantiationAwareBeanPostProcessor类型的BeanPostProcessor执行，即执行一种类型的后置处理器，先执行postProcessBeforeInstantiation，如果该方法返回了一个bean，那么再执行applyBeanPostProcessorsAfterInitialization方法
- 如果该方法没有返回一个bean，采用doCreateBean(beanName, mbdToUse, args)方法生成一个bean实例，对于doCreateBean()方法流程如下：
- 首先利用反射创建该bean
- 然后bean创建后，让MergedBeanDefinitionPostProcessor的BeanPostProcessor执行，执行其postProcessMergedBeanDefinition方法
- 然后再调用populateBean()方法为bean的属性赋值，在属性赋值之前会让InstantiationAwareBeanPostProcessor的postProcessAfterInstantiation、postProcessPropertyValues方法执行，然后再调用applyPropertyValues为bean的属性赋值
- 属性赋值后，调用initializeBean()对bean进行初始化
- invokeAwareMethods(beanName, bean);执行xxxAware接口的方法，从而可以使用户实现ioc容器内部组件的获取
- 执行BeanPostProcessor的postProcessBeforeInitialization方法
- 初始化bean
- 执行BeanPostProcessor的postProcessAfterInitialization方法
- 注册bean的销毁方法
- 将创建的bean加入到IOC容器中
- 注：ioc容器其实就是一些Map集合，这些集合保存了单实例Bean，环境信息等因素
2). 获取容器中的所有bean，利用for循环依次判断其是否为SmartInitializingSingleton类型，如果是则调用afterSingletonsInstantiated方法
11.finishRefresh()
完成BeanFactory的初始化创建工作，IOC容器就创建完成
protected void finishRefresh() {
// Initialize lifecycle processor for this context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
getLifecycleProcessor().onRefresh();
// Publish the final event.
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
该步主要完成以下工作：
- initLifecycleProcessor():初始化和生命周期有关的后置处理器，并将其加入IOC容器
- 拿到之前加入的生命周期后置处理器，并回调其onRefresh()方法
- publishEvent(new ContextRefreshedEvent(this))；发布容器刷新完成事件
总结
1) Spring容器在启动的时候，先会保存所有注册进来的Bean的定义信息，无论是采用xml注册Bean还是使用注解（@Bean、@Service...） 2) Spring会在合适的时机获取这些Bean的信息并进行创建，创建完成后加入容器以便后续调用2.1)第一个时机：用到这个bean的时候，会调用getBean()创建，然后保存
2.2)第二个时机：统一创建所有剩下的单实例Bean,即finishBeanFactoryInitialization(beanFactory
每一个Bean创建完成，都会使用各种后置处理器进行处理，从而增强Bean
例如AutowiredAnnotationBeanPostProcessor，用于处理自动注入
例如AnnotationAwareAspectJAutoProxyCreator，用于AOP