1.启动Spring 应用,创建ApplicationContext
@Test
public void test01(){
AnnotationConfigApplicationContext applicationContext =
new AnnotationConfigApplicationContext(MainConfigOfAOP.class);
applicationContext.close();
} public AnnotationConfigApplicationContext(Class<?>... annotatedClasses) {
this();
register(annotatedClasses);
refresh();
}2.Spring 启动的主要代码(AnnotationConfigApplicationContext)
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// 注册Bean 的后置处理器,来拦截Bean 的创建
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
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();
}
}
}3.主要研究下后置处理器的注册过程(PostProcessorRegistrationDelegate)
- 从容器中拿到所有BeanPostProcessor类型的BeanName数组
- 遍历上面拿到的数组,根据是否实现了PriorityOrdered,Ordered 接口,以及没有实现这两个接口, 将BeanPostProcessor类型的BeanName数组分成3类
- 首先处理实现了PriorityOrdered接口的后置处理器,先从beanFactory中尝试获取当前beanname对应的对象,如果beanFactory中当前还不存在,则触发创建过程
- 将获取到的对象加入List(priorityOrderedPostProcessors)中,并判断此对象是否是MergedBeanDefinitionPostProcessor类型的,如果是,也将这个对象加入到另外的一个List(internalPostProcessors)中.
- 将priorityOrderedPostProcessors按优先级排序,再将其注册到beanFactory中
- 接下来,已相同的流程处理实现了Ordered接口的后置处理器
- 最终处理没有实现上面两个接口的后置处理
- 将internalPostProcessors中的后置处理器再排序,再次注册到beanFactory 中
- 在beanFactory后置处理器的最后, 再手动注册一个ApplicationListenerDetector的后置处理器
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 从容器中获取所有的BeanPostProcessor类型的BeanName数组
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));
// 分离实现了PriorityOrdered,Ordered 接口的BeanPostProcessors 和其他类型的BeanPostProcessors
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<BeanPostProcessor>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<BeanPostProcessor>();
List<String> orderedPostProcessorNames = new ArrayList<String>();
List<String> nonOrderedPostProcessorNames = new ArrayList<String>();
// 循环前面获取到的BeanPostProcessor数组
for (String ppName : postProcessorNames) {
// 如果当前类实现了 PriorityOrdered 接口
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
// 尝试从容器中获取该类型的对象(如果容器中没有,则会开始创建)
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
// 将创建出来的后置处理器添加到priorityOrderedPostProcessors 的List中
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
// 如果实现了 Ordered 接口,则将全类名添加到orderedPostProcessorNames的List中
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
// 否则添加全类名到 nonOrderedPostProcessorNames 的List 中
nonOrderedPostProcessorNames.add(ppName);
}
}
//首先,注册实现了PriorityOrdered接口的接口
//先排序后置处理器
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
//再进行注册
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// 然后,注册实现了Ordered 接口的后置处理器
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);
// 最后注册所有常规的 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);
//最后, 再次注册所有的内部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));
}3.1注册后置处理器代码(PostProcessorRegistrationDelegate)
private static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {
for (BeanPostProcessor postProcessor : postProcessors) {
beanFactory.addBeanPostProcessor(postProcessor);
}
}4. Bean 的创建过程
由于Spring 第一启动,容器中也不存在已经创建好的BeanPostProcessor, 所以需要新创建,下面为其创建过程
protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {
// 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 != null ? instanceWrapper.getWrappedInstance() : null);
Class<?> beanType = (instanceWrapper != null ? instanceWrapper.getWrappedClass() : null);
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, new ObjectFactory<Object>() {
@Override
public Object getObject() throws BeansException {
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
// 为创建的Bean赋值
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
// 初始化Bean,调用相应的初始化代码
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<String>(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;
}4.1调用初始化过程
protected Object initializeBean(final String beanName, final Object bean, RootBeanDefinition mbd) {
if (System.getSecurityManager() != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
@Override
public Object run() {
invokeAwareMethods(beanName, bean);
return null;
}
}, getAccessControlContext());
}
else {
invokeAwareMethods(beanName, bean);
}
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
// BeanPostProcessors 的Before 方法
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// 调用初始化方法
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()) {
// BeanPostProcessors 的After方法
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}4.2 查看当前类是否实现了Aware接口,再根据具体的类型,强转后,注入对应的内容(AbstractAutowireCapableBeanFactory)
private void invokeAwareMethods(final String beanName, final Object bean) {
if (bean instanceof Aware) {
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
}
if (bean instanceof BeanFactoryAware) {
((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
}
}
}4.3 创建的每个对象,都将被传到后置处理器的(before/after)方法中
@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
throws BeansException {
// 将传入的Bean 应用到所有的后置处理器中
Object result = existingBean;
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
result = beanProcessor.postProcessBeforeInitialization(result, beanName);
//如果其中某一个后置处理器返回为null,则后续的后置处理器将不再调用,而直接返回
if (result == null) {
return result;
}
}
return result;
}
@Override
public Object applyBeanPostProcessorsAfterInitialization(Object existingBean, String beanName)
throws BeansException {
Object result = existingBean;
for (BeanPostProcessor beanProcessor : getBeanPostProcessors()) {
result = beanProcessor.postProcessAfterInitialization(result, beanName);
if (result == null) {
return result;
}
}
return result;
}4.4 调用初始化方法
protected void invokeInitMethods(String beanName, final Object bean, RootBeanDefinition mbd)
throws Throwable {
boolean isInitializingBean = (bean instanceof InitializingBean);
if (isInitializingBean && (mbd == null || !mbd.isExternallyManagedInitMethod("afterPropertiesSet"))) {
if (logger.isDebugEnabled()) {
logger.debug("Invoking afterPropertiesSet() on bean with name '" + beanName + "'");
}
if (System.getSecurityManager() != null) {
try {
AccessController.doPrivileged(new PrivilegedExceptionAction<Object>() {
@Override
public Object run() throws Exception {
((InitializingBean) bean).afterPropertiesSet();
return null;
}
}, getAccessControlContext());
}
catch (PrivilegedActionException pae) {
throw pae.getException();
}
}
else {
// 如果当前bean实现了InitializingBean 接口,此接口的方法将在此被调用
((InitializingBean) bean).afterPropertiesSet();
}
}
if (mbd != null) {
String initMethodName = mbd.getInitMethodName();
if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
//调用自定义的init-method 方法(xml中配置的,或@Bean注解中配置的)
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}5. Spring Bean 生命周期
