spring初始化refresh()方法中obtainFreshBeanFactory()源码走读。

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简述obtainFreshBeanFactory()方法：

分析ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();方法

描述：该方法主要是解析我们项目配置的 application.xml、xxx.xml 定义的import、bean、resource、profile、、、、、。

这里我们就简单的分析下解析XML

1、解析<bean id="" classs="" 、、、、/>将element属性赋值到对应的AbstractBeanDefinition 定义的对象中

2、将AbstractBeanDefinition继续赋值给一个BeanDefinitionHolder（包含aliases、beanName、beanDefinition（就是我们AbstractBeanDefinition））

3、或取BeanDefinitionHolder对象的beanName和beanDefinition 将其注册到BeanDefinitionRegistry对象中（其实里面就是将beanName 添加到List<String>

，将beanName--key和beanDefinition--value 保存到 Map<String, BeanDefinition> 中。）

目标：其实这个方法的核心就是解析XML 或扫描注解将其属性封装到BeanDefinition 对象中，并对它beanName(key) BeanDefinition(v) 保存到一个Map 中，这个obtainFreshBeanFactory()的工作

就完成了，这就保证了后面spring加载依赖注入提供了对应的元数据。

=========================开始=================================

类：org.springframework.context.support.AbstractApplicationContext

@Override
public void refresh() throws BeansException, IllegalStateException {

synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.

//prepareRefresh()方法调用链路--->initPropertySources();
　　　 //                         ---->AbstractRefreshableWebApplicationContext.initPropertySources()
  　　//                                --->StandardServletEnvironment.initPropertySources()
  　　// 主要作用就是通过StandardServletEnvironment类 获取到web.xml中<context-param>--xxx/applicationContext.xml　的参数信息
      //启动打印日志 DEBUG o.s.w.c.s.StandardServletEnvironment - Initialized StandardServletEnvironment with PropertySources [serv      //             letConfigInitParams,servletContextInitParams,systemProperties,systemEnvironment]

prepareRefresh();
// Tell the subclass to refresh the internal bean factory.

//创建BeanFactory，如果已有就销毁，没有就创建。此类实现了对BeanDefinition的装载

  
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();

// Initialize event multicaster for this context.
initApplicationEventMulticaster();

// Initialize other special beans in specific context subclasses.
onRefresh();

// Check for listener beans and register them.
registerListeners();

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

// Last step: publish corresponding event.
finishRefresh();
      }

catch (BeansException ex) {
logger.warn("Exception encountered during context initialization - cancelling refresh attempt", ex);

// Destroy already created singletons to avoid dangling resources.
destroyBeans();

// Reset 'active' flag.
cancelRefresh(ex);

// Propagate exception to caller.
throw ex;
      }

finally {
// Reset common introspection caches in Spring's core, since we
         // might not ever need metadata for singleton beans anymore...
resetCommonCaches();
      }
   }
}

----》分析ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();方法