Spring Ioc 容器 创建Bean 的流程
1、Spring 版本 3.1
2、BeanFactory 创建bean 流程:
以 DefaultListableBeanFactory 为例说明BeanFactory 创建bean的流程。 DefaultListableBeanFactory是Spring提供的两个重要的BeanFactory的实现
2.1、当我们调用类似 DefaultListableBeanFactory 的getBean(...) 方法时候、 会去调用其父类AbstractAutowireCapableBeanFactory 的 createBean(...) 方法：
2.2、 AbstractAutowireCapableBeanFactory 的 createBean 如下：
protected Object createBean( final String beanName, final RootBeanDefinition mbd,
final Object[] args) throws BeanCreationException {
.... // 省略
// Make sure bean class is actually resolved at this point.
resolveBeanClass(mbd, beanName); // 2.2.1 .解析Bean的 class
// Prepare method overrides.
try {
mbd.prepareMethodOverrides(); // 2.2.2 ???
} catch (BeanDefinitionValidationException ex) {
.... // 省略
}
try {
// Give BeanPostProcessors a chance to return a proxy instead of the target bean instance.
// 2.2.3. BeanPostProcessor扩展点 ,会回调BeanPostProcessor接口中定义的
postProcessBeforeInstantiation 和 postProcessAfterInstantiation
Object bean = resolveBeforeInstantiation(beanName, mbd);
if (bean != null ) {
return bean; // 2.2.4. 如果2.2.3处的扩展点返回的bean不为空，直接返回该bean ，后续流程不执行
}
} catch (Throwable ex) {
... // 省略
}
Object beanInstance = doCreateBean(beanName, mbd, args); //2.2.5. 执行创建bean实例的流程
... // 省略
return beanInstance;
}
注意： 2.2.3、 BeanPostProcessor 扩展点（只有 InstantiationAwareBeanPostProcessor 接口的实现才会被调 用）
2.3、 AbstractAutowireCapableBeanFactory 的 doCreateBean方法代码如下：
protected Object doCreateBean ( final String beanName, final RootBeanDefinition mbd,
final Object[] args) {
//2.3.1、构造Bean，并返回bean 的 BeanWrapper 类
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 );
// Allow post-processors to modify the merged bean definition.
//2.3.2、回调 MergedBeanDefinitionPostProcessor的postProcessMergedBeanDefinition接口
synchronized (mbd. postProcessingLock ) {
if (!mbd. postProcessed ) {
applyMergedBeanDefinitionPostProcessors(mbd, beanType, beanName);
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) {
// ... 省略日志
addSingletonFactory(beanName, new ObjectFactory() {
public Object getObject() throws BeansException {
// 2.3.3、回调SmartInstantiationAwareBeanPostProcessor的getEarlyBeanReference 接口
return getEarlyBeanReference(beanName, mbd, bean);
}
});
}
// Initialize the bean instance.
Object exposedObject = bean;
try {
// 2.3.4、组装-Bean依赖
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null ) {
// 2.3. 5、初始化Bean
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
} catch (Throwable ex) {
// ... 省略
}
if (earlySingletonExposure) {
// ... 省略部分代码, 代码用途???
}
// Register bean as disposable.
// 注册Bean的销毁回调
try {
registerDisposableBeanIfNecessary(beanName, bean, mbd);
} catch (BeanDefinitionValidationException ex) {
// ... 省略
}
return exposedObject;
}
2.4、 AbstractAutowireCapableBeanFactory 的 populateBean方法代码如下:
protected void populateBean(String beanName, AbstractBeanDefinition mbd,
BeanWrapper bw) {
PropertyValues pvs = mbd.getPropertyValues();
if (bw == null ) {
if (!pvs.isEmpty()) {
// ... 省略
} else {
// Skip property population phase for null instance.
return ;
}
}
// Give any InstantiationAwareBeanPostProcessors the opportunity to modify the
// state of the bean before properties are set. This can be used, for example,
// to support styles of field injection.
boolean continueWithPropertyPopulation = true ;
if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp =
(InstantiationAwareBeanPostProcessor) bp;
if (!ibp.postProcessAfterInstantiation(bw.getWrappedInstance(), beanName)) {
continueWithPropertyPopulation = false ;
break ;
}
}
}
}
if (!continueWithPropertyPopulation) {
return ;
}
// 2.4.1 根据name或type 自动装配
if (mbd.getResolvedAutowireMode() == RootBeanDefinition. AUTOWIRE_BY_NAME ||
mbd.getResolvedAutowireMode() == RootBeanDefinition. AUTOWIRE_BY_TYPE ) {
MutablePropertyValues newPvs = new MutablePropertyValues(pvs);
// Add property values based on autowire by name if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition. AUTOWIRE_BY_NAME ) {
autowireByName(beanName, mbd, bw, newPvs);
}
// Add property values based on autowire by type if applicable.
if (mbd.getResolvedAutowireMode() == RootBeanDefinition. AUTOWIRE_BY_TYPE ) {
autowireByType(beanName, mbd, bw, newPvs);
}
pvs = newPvs;
}
boolean hasInstAwareBpps = hasInstantiationAwareBeanPostProcessors();
boolean needsDepCheck = (mbd.getDependencyCheck()
!=RootBeanDefinition. DEPENDENCY_CHECK_NONE );
if (hasInstAwareBpps || needsDepCheck) {
PropertyDescriptor[] filteredPds = filterPropertyDescriptorsForDependencyCheck(bw);
//2.4.2、执行InstantiationAwareBeanPostProcessor的postProcessPropertyValues
if (hasInstAwareBpps) {
for (BeanPostProcessor bp : getBeanPostProcessors()) {
if (bp instanceof InstantiationAwareBeanPostProcessor) {
InstantiationAwareBeanPostProcessor ibp =
(InstantiationAwareBeanPostProcessor) bp;
pvs = ibp.postProcessPropertyValues(pvs, filteredPds,
bw.getWrappedInstance(), beanName);
if (pvs == null ) {
return ;
}
}
}
}
//2.4.3、执行依赖检查
if (needsDepCheck) {
checkDependencies(beanName, mbd, filteredPds, pvs);
}
//2.4.4、应用明确的setter属性注入
applyPropertyValues(beanName, mbd, bw, pvs);
}
注意： 2.4.2、 执行其它的依赖注入， 当Spring 配置文件中有<context:annotation-config/> 这样的标签，并且
使用Spring 的ApplicationContext 容器(BeanFactory 不会自动注册) 会自动注册一些内置的
BeanPostProcessors, 这些BeanPostProcessesors 将会在此处用到，完成一些注入工作。
a、AutowiredAnnotationBeanPostProcessor 执行@Autowired注入
b、CommonAnnotationBeanPostProcessor 执行@Resource 注入
c、 RequiredAnnotationBeanPostProcessor 执行@Required 的注入检查
2.5、 AbstractAutowireCapableBeanFactory 的 initializeBean方法代码如下：
protected Object initializeBea( final String beanName, final Object bean,
RootBeanDefinition mbd) {
//此处省略部分代码
//2.5.1、调用Aware接口注入（BeanNameAware、BeanClassLoaderAware、BeanFactoryAware）
invokeAwareMethods(beanName, bean);
// 2.5.2、回调BeanPostProcessor的postProcessBeforeInitialization接口 修改Bean
Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
//2.5. 3、执行初始化回调（1、调用InitializingBean的afterPropertiesSet 2、调用自定义的init-method）
try {
invokeInitMethods(beanName, wrappedBean, mbd);
} catch (Throwable ex) {
//...异常省略
}
//2.5.4、回调BeanPostProcessor的postProcessAfterInitialization接口修改Bean
if (mbd == null || !mbd.isSynthetic()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}
注意： 2.5.2、 当使用Spring的ApplicationContext 容器(BeanFactory 不会自动注册) 、会自动注册一些内置的
BeanPostProcessors, 这些BeanPostProcessesors 将会在此处用到，完成一些初始化的工作。
1、ApplicationContextAwareProcesso r 回调一些Aware接口 如：
EnvironmentAware，EmbeddedValueResolverAware, ResourceLoaderAware,
ApplicationEventPublisherAware,MessageSourceAware,ApplicationContextAware
2、 CommonAnnotationBeanPostProcessor 配置文件包含 <context:annotation-config/>时候
会 调用有@PostConstruct Annotation 初始化的方法。
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.
// 3.2.1为BeanFactory 注册一些内部 BeanPostProcess 如
// (ApplicationContextAwareProcessor)
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
// 3.2.2 调用 在配置文件中定义的 BeanFactoryPostProcessor bean 方法的 // postProcessBeanFactory(...) 方法
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
// 3.2.3 注册内部的BeanPostProcessors 如有<context:annotation-config/>
// 这个标签将注册如下 BeanPostProcessors:
//AutowiredAnnotationBeanPostProcessor,CommonAnnotationBeanPostProcessor
//RequiredAnnotationBeanPostProcessor 等.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
// 3.2.4 初始化ApplicationContext 内部的 MessageSource
initMessageSource();
// Initialize event multicaster for this context.
// 3.2.5 初始化ApplicationContext 内部的 applicationEventMulticaster
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
// 3.2.6 注册 ApplicationListeners 在配置文件cotext 中查找ApplcationListeners
// 并注册他们。
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
// 3.2.7 初始化配置文件 context 中的所有的singleton 并且lazy-init="false"的bean
// 如果scope 不是singleton, bean将不会初始化
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
// 3.2.8 初始化 lifecycle processor，调用LifecycleProcessor 的onRefresh() 方法
// publish ContextRefreshedEvent;
finishRefresh();
}
catch (BeansException ex) {
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
}
}
3.3 然后接下来流程将调用BeanFactory 创建Bean 的方法.