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