spring学习----bean实例化

实例化相关核心类

AbstractBeanFactory 实现getBean

AbstractAutowireCapableBeanFactory 实现createBean（即实例化bean）

bean生命周期

bean实例创建

为bean实例设置属性

调用bean的初始化方法

应用通过IOC容器使用bean

容器关闭时，调用销毁方法destory

bean实例化入口getBean()方法

AbstractBeanFactory实现getBean()–>doGetBean–>createBean()

子类AbstractAutowireCapableBeanFactory实现createBean–>doCreateBean

1、createBeanInstance方法创建bean（JVM反射  cglib具体参考源码）
1、populateBean方法（依赖注入，先执行autowire注解，在执行property注入依赖）
2、initializeBean()初始化bean
第一步判断是否实现BeanNameAware、BeanClassLoaderAware、BeanFactoryAware接口执行相应set方法
第二步执行实现BeanPostProcessor接口的前置方法postProcessBeforeInitialization
第三步执行初始化方法
是否实现InitializingBean若实现先执行afterProperties方法
执行指定init方法
第四步执行实现BeanPostProcessor接口的后置方法postProcessAfterInitialization

注意：

getBean先从缓存了查找，有直接获取，没有创建已bean实例

doGetBean中判断是否有依赖，若有，先实例化依赖bean（getBean递归实现）

相应源码

依赖递归实现AbstractBeanFactory doGetBean

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);
}
}

AbstractAutowireCapableBeanFactory实例化实现类 doCreateBean

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 {
populateBean(beanName, mbd, instanceWrapper);
if (exposedObject != null) {
exposedObject = initializeBean(beanName, exposedObject, mbd);
}
}
...

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()) {
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}

try {
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()) {
wrappedBean = applyBeanPostProcessorsAfterInitialization(wrappedBean, beanName);
}
return wrappedBean;
}

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 {
((InitializingBean) bean).afterPropertiesSet();
}
}

if (mbd != null) {
String initMethodName = mbd.getInitMethodName();
if (initMethodName != null && !(isInitializingBean && "afterPropertiesSet".equals(initMethodName)) &&
!mbd.isExternallyManagedInitMethod(initMethodName)) {
invokeCustomInitMethod(beanName, bean, mbd);
}
}
}

bean对容器感知

通过实现aware接口 set方法 实际执行时机initializeBean方法

BeanNameAware

BeanClassLoaderAware

BeanFactoryAware

ResourceLoaderAware

ApplicationContextAware

MessageSourceAware

ApplicationEventPublisherAware

ApplicationContextAwareProcessor （实现BeanPostProcessor接口）

使bean能通过实现Aware接口set方法获取容器相关高级特性

private void invokeAwareInterfaces(Object bean) {
if(bean instanceof Aware) {
if(bean instanceof EnvironmentAware) {
((EnvironmentAware)bean).setEnvironment(this.applicationContext.getEnvironment());
}

if(bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware)bean).setEmbeddedValueResolver(this.embeddedValueResolver);
}

if(bean instanceof ResourceLoaderAware) {
((ResourceLoaderAware)bean).setResourceLoader(this.applicationContext);
}

if(bean instanceof ApplicationEventPublisherAware) {
((ApplicationEventPublisherAware)bean).setApplicationEventPublisher(this.applicationContext);
}

if(bean instanceof MessageSourceAware) {
((MessageSourceAware)bean).setMessageSource(this.applicationContext);
}

if(bean instanceof ApplicationContextAware) {
((ApplicationContextAware)bean).setApplicationContext(this.applicationContext);
}
}

}