spring ioc实现原理

spring ioc实现原理

1、一个普通的调用

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
GsonFormatBean bean = (GsonFormatBean) context.getBean("GsonFormatBean");
bean.isPalindrome(100);

1.1 分析第一步

 创建一个classPathXmlApplication的context，主要的实现在abstractAppplicationContext的refresh()这个方法中

	@Override
	public void refresh() throws BeansException, IllegalStateException {
		synchronized (this.startupShutdownMonitor) {
			// Prepare this context for refreshing.
			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			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) {
				if (logger.isWarnEnabled()) {
					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();
			}
		}
	}

使用对象锁保证只有一个线程访问逻辑

 第一步：

设置容器的一些全局性参数，比如closed，active等参数

第二步：

告诉父类创建一个bean工厂

 刷新整个bean工厂，获取一个ConfigurableListableBeanFacotory，返回bean工厂。

刷新beanFactory

 创建一个DefaultListableBeanFactory，设置一些属性，加载beanDefinition，具体的实现在abstractxmlApplicationContext、AnnotationWebConfigApplicationContext等

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容器怎么实现加载所有的bean

 两个关键的方法：

 容器注册所有的beanDefinitions

解析单个bean的操作 

 最终生成beanDefination，也就是将xml映射成为一个bean

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