Spring中的Aware作用以及源码

文章目录

• ​​1.源码​​
• ​​2.Aware调用链​​
• ​​3.initializeBean 初始化Bean​​

在有些场景中我们需要感知到容器的存在，需要获取容器的工具类，这个时候需要使用Spring Aware提供的工具类

Spring 框架中提供许多实现Aware接口的类，这些类主要是为了辅助Spring访问容器中的数据

1.源码

自定义实现ApplicationContextAware接口类，然后在setApplicationContext方法打断点，debug模式下查看堆栈信息

2.Aware调用链

createBean - doCreateBean - initializeBean - applyBeanPostProcessorsBeforeInitialization - invokeAwareInterfaces

3.initializeBean 初始化Bean

protected Object initializeBean(String beanName, Object bean, @Nullable RootBeanDefinition mbd) {
  if (System.getSecurityManager() != null) {
    AccessController.doPrivileged((PrivilegedAction

invokeAwareMethods,applyBeanPostProcessorsBeforeInitialization

invokeAwareMethods 对ware执行分类

private void invokeAwareMethods(String beanName, Object bean) {
  if (bean instanceof Aware) {
    if (bean instanceof BeanNameAware) {
      ((BeanNameAware) bean).setBeanName(beanName);
    }
    if (bean instanceof BeanClassLoaderAware) {
      ClassLoader bcl = getBeanClassLoader();
      if (bcl != null) {
        ((BeanClassLoaderAware) bean).setBeanClassLoader(bcl);
      }
    }
    if (bean instanceof BeanFactoryAware) {
      ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
    }
  }
}

applyBeanPostProcessorsBeforeInitialization 获取所有的执行器，依次执行

@Override
public Object applyBeanPostProcessorsBeforeInitialization(Object existingBean, String beanName)
    throws BeansException {

  Object result = existingBean;
  for (BeanPostProcessor processor : getBeanPostProcessors()) {
    Object current = processor.postProcessBeforeInitialization(result, beanName);
    if (current == null) {
      return result;
    }
    result = current;
  }
  return result;
}