Spring aware相关接口 浅析

spring中 有一大堆Aware结尾接口, 例如BeanFactoryAware, ApplicationContextAware, ServletContextAware等

在程序中 我们自定义的bean实现了 Aware相关接口 spring 通过回调 就可以获得一些资源

比如说 我们的bean实现BeanFactoryAware spring会在bean实例化(getBean)阶段 回调该setBeanFactory方法 注入BeanFactory实例(也就是this)

spring BeanFactoryAware 接口定义

public interface BeanFactoryAware {

void setBeanFactory(BeanFactory beanFactory) throws BeansException;

}

spring容器中的bean 实例化 是在AbstractBeanFactory getBean中发生

public Object getBean(String name, Class requiredType, Object[] args) throws BeansException {
return doGetBean(name, requiredType, args, false);
}

调用的 doGetBean 方法比较复杂 简单看看 创建单例这段

protected Object doGetBean(
final String name, final Class requiredType, final Object[] args, boolean typeCheckOnly) throws BeansException {

final String beanName = transformedBeanName(name);
.................略			// Create bean instance.
//bean的定义是不是单例
if (mbd.isSingleton()) {
sharedInstance = getSingleton(beanName, new ObjectFactory() {
public Object getObject() throws BeansException {
try {
// 是一个抽象方法  在子类AbstractAutowireCapableBeanFactory中实现
return createBean(beanName, mbd, args);
}
catch (BeansException ex) {
destroySingleton(beanName);
throw ex;
}
}
});
bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
}

.................略
return bean;
}

AbstractAutowireCapableBeanFactory createBean方法

protected Object createBean(final String beanName, final RootBeanDefinition mbd, final Object[] args)
throws BeanCreationException {

AccessControlContext acc = AccessController.getContext();
return AccessController.doPrivileged(new PrivilegedAction() {
public Object run() {
.................略
//关注doCreateBean方法
Object beanInstance = doCreateBean(beanName, mbd, args);
if (logger.isDebugEnabled()) {
logger.debug("Finished creating instance of bean '" + beanName + "'");
}
return beanInstance;
}
}, acc);
}

doCreateBean方法

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd, final Object[] args) {
// Instantiate the bean.
BeanWrapper instanceWrapper = null;
if (mbd.isSingleton()) {
instanceWrapper = (BeanWrapper) this.factoryBeanInstanceCache.remove(beanName);
}
.................略
// Initialize the bean instance.
Object exposedObject = bean;
try {
populateBean(beanName, mbd, instanceWrapper);
//实现 *Aware部分接口， InitializingBean接口  方法调用在此发生
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);
}
}

.................略
return exposedObject;
}

initializeBean方法

protected Object initializeBean(String beanName, Object bean, RootBeanDefinition mbd) {
if (bean instanceof BeanNameAware) {
((BeanNameAware) bean).setBeanName(beanName);
}
if (bean instanceof BeanClassLoaderAware) {
((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
}
// 如果当前bean 是BeanFactoryAware的一个实例
if (bean instanceof BeanFactoryAware) {
//回调当前实例注入资源
((BeanFactoryAware) bean).setBeanFactory(this);
}

Object wrappedBean = bean;
if (mbd == null || !mbd.isSynthetic()) {
//BeanPostProcessor 接口  postProcessBeforeInitialization方法回调
wrappedBean = applyBeanPostProcessorsBeforeInitialization(wrappedBean, beanName);
}
try {
// 实现InitializingBean接口  afterPropertiesSet方法调用
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;
}

Spring aware相关接口