Spring源碼分析總結(一)-IOC容器初始化
IOC容器的初始化是由refresh()方法啟動。經常使用的ApplicationContext 有:ClassPathXmlApplicationContext和FileSystemXmlApplicationContext、XmlWebApplicationContext等。都有refresh()方法。
refresh()方法的這個啟動分為三個基本過程:
/**
* Create a new ClassPathXmlApplicationContext with the given parent,
* loading the definitions from the given XML files.
* @param configLocations array of resource locations
* @param refresh whether to automatically refresh the context,
* loading all bean definitions and creating all singletons.
* Alternatively, call refresh manually after further configuring the context.
* @param parent the parent context
* @throws BeansException if context creation failed
* @see #refresh()
*/
public ClassPathXmlApplicationContext(
String[] configLocations, boolean refresh, @Nullable ApplicationContext parent)
throws BeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}public abstract class AbstractApplicationContext extends DefaultResourceLoader
implements ConfigurableApplicationContext {@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//準備刷新的上下文環境 Prepare this context for refreshing.
prepareRefresh();
//初始化BeanFactory,並進行xml文件讀取 Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
//對BeanFactory進行各種功能填充 Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
//子類覆蓋方法做額外的處理Allows post-processing of the bean factory in context subclasses. postProcessBeanFactory(beanFactory);
//激活各種BeanFactory處理器器,這裏只是註冊調用在getBean()的時候 Invoke factory processors registered as beans in the context.
invokeBeanFactoryPostProcessors(beanFactory);
//註冊攔截Bean創建的Bean處理,這裏只是註冊調用在getBean()的時候
//Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
//為上下文初始化message源,即不同語言的消息體,國際化處理 Initialize message source for this context.
initMessageSource();
//初始化應用消息廣播器,並放入（applicationEventMulticaster） Initialize event multicaster for this context.
initApplicationEventMulticaster();
//留給子類來初始化其他的Bean Initialize other special beans in specific context subclasses.
onRefresh();
//在所有註冊的bean中查找Listener bean註冊到消息廣播器中。 Check for listener beans and register them.
registerListeners();
//初始化剩下的單實例(非惰性的) Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);
//完成刷新過程,通知生命周期處理器lifecycleProcessor刷新過程, 同時發出ContextRefreshEvent通知別人。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();
}
}
}}
ApplicationContext factory = new FileSystemXmlApplicationContext("F:/workspace/example/src/appcontext.xml");
IHelloWorld hw = (IHelloWorld)factory.getBean("helloworldbean");
log.info(hw.getContent("luoshifei")); //用classpath路徑
ApplicationContext factory = new ClassPathXmlApplicationContext("classpath:appcontext.xml");
Ioc容器的初始化
1、第一個過程 BeanDefinition的Resource定位
FileSystemXmlApplicationContext/ClassPathXmlApplicationContext ->AbstractApplicationContext類refresh()
->調用AbstractRefreshableApplicationContext類的refreshBeanFactory()->調用了loadBeanDefinitions(beanFactory);
->XmlWebApplicationContext類的loadBeanDefinitions->XmlBeanDefinitionReader類的loadBeanDefinitions
->AbstractBeanDefinitionReader類的loadBeanDefinitions
==>1.調用DefaultResourceLoader的getResource完成具體的Resource定位(Resource resource = resourceLoader.getResource(location);)
->DefaultResourceLoader類的getResourceByPath(location)完成Resource的定位
==>2.如果跟ResourcePatternResolver相同 ->調用PathMatchingResourcePatternResolver類的getResources方法
在XmlBeanDefinitionReader的基類AbstractBeanDefinition加載讀入BeanDefinition
2、第二個過程 BeanDefinition的載入和解析
AbstractRefreshableApplicationContext類的refreshBeanFactory()->XmlWebApplicationContext類的loadBeanDefinitions
->AbstractBeanDefinitionReader類的loadBeanDefinitions
->XmlBeanDefinitionReader類的loadBeanDefinitions()->loadBeanDefinitions()-裏面的doLoadBeanDefinitions
->registerBeanDefinitions(doc, resource)->documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
->DefaultBeanDefinitionDocumentReader類的registerBeanDefinitions方法->doRegisterBeanDefinitions(root);
->parseBeanDefinitions(root, this.delegate);->parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate)
->parseDefaultElement(ele, delegate);->processBeanDefinition(ele, delegate);
->delegate.parseBeanDefinitionElement(ele);->BeanDefinitionParserDelegate類的parseBeanDefinitionElement(ele, null);
->BeanDefinitionParserDelegate類parseBeanDefinitionElement方法
3、第三個過程 BeanDefinition在IOC容器中的註冊
把解析得到的BeanDefinition設置到hashMap中去。
在DefaultListableBeanFactory中,事通過一個HashMap來持有載入的BeanDefinition的，這個HashMap的定義在DefaultListableBeanFactory中可以看到。
IOC容器的依賴註入
1、當用戶向IOC容器索要Bean時,也就是如：
IHelloWorld hw = (IHelloWorld)factory.getBean("helloworldbean");從DefaultListableBeanFactory的基類AbstractBeanFactory類可以看getBean的實現。
//---------------------------------------------------------------------
// Implementation of BeanFactory interface
//---------------------------------------------------------------------
@Override
public Object getBean(String name) throws BeansException {
return doGetBean(name, null, null, false);
}
在createBeanInstance中生成了Bean所包含的java對象,這個對象的生成方式有很多方式,可以通過工廠方法,也可以通過容器的Autowire特性生成,由相關的BeanDefinition來指定。
SimpleInstantiationStrategy類,這個Strategy是spring用來生成bean對象的默認類,它提供了兩種實例化Java對象的方法，一種是通過BeanUtils,它提供了JVM的反射功能，一種是通過CGLIB生成。
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Spring源碼分析總結(一)-IOC容器初始化