一直在使用spring，却从未整理过spring，现在从源码上整理下，也方便自己以后查阅。
1.如果是spring的web项目，那么web.xml中会有如下一段配置
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
2.web容器初始化会触发ContextLoaderListener#contextInitialized被调用
public void contextInitialized(ServletContextEvent event) {
this.contextLoader = this.createContextLoader();
if (this.contextLoader == null) {
this.contextLoader = this;
}
this.contextLoader.initWebApplicationContext(event.getServletContext());
}
3.contextInitialized内部会继续调用initWebApplicationContext
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
throw new IllegalStateException("Cannot initialize context because there is already a root application context present - check whether you have multiple ContextLoader* definitions in your web.xml!");
} else {
Log logger = LogFactory.getLog(ContextLoader.class);
servletContext.log("Initializing Spring root WebApplicationContext");
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
long startTime = System.currentTimeMillis();
try {
if (this.context == null) {
this.context = this.createWebApplicationContext(servletContext);
}
if (this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext)this.context;
if (!cwac.isActive()) {
if (cwac.getParent() == null) {
ApplicationContext parent = this.loadParentContext(servletContext);
cwac.setParent(parent);
}
this.configureAndRefreshWebApplicationContext(cwac, servletContext);
}
}
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl == ContextLoader.class.getClassLoader()) {
currentContext = this.context;
} else if (ccl != null) {
currentContextPerThread.put(ccl, this.context);
}
if (logger.isDebugEnabled()) {
logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" + WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
}
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
}
return this.context;
} catch (RuntimeException var8) {
logger.error("Context initialization failed", var8);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, var8);
throw var8;
} catch (Error var9) {
logger.error("Context initialization failed", var9);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, var9);
throw var9;
}
}
}
4.核心方法configureAndRefreshWebApplicationContext
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
String configLocationParam;
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
configLocationParam = sc.getInitParameter("contextId");
if (configLocationParam != null) {
wac.setId(configLocationParam);
} else if (sc.getMajorVersion() == 2 && sc.getMinorVersion() < 5) {
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(sc.getServletContextName()));
} else {
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(sc.getContextPath()));
}
}
wac.setServletContext(sc);
configLocationParam = sc.getInitParameter("contextConfigLocation");
if (configLocationParam != null) {
wac.setConfigLocation(configLocationParam);
}
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment)env).initPropertySources(sc, (ServletConfig)null);
}
this.customizeContext(sc, wac);
wac.refresh();
}
5.核心方法refresh
public void refresh() throws BeansException, IllegalStateException {
Object var1 = this.startupShutdownMonitor;
synchronized(this.startupShutdownMonitor) {
// 准备阶段，初始化配置文件、以及系统环境变量验证
this.prepareRefresh();
// ConfigurableListableBeanFactory是spring容器的BeanFactory以及定位xml解析xml
// 注册到beanFactory
ConfigurableListableBeanFactory beanFactory = this.obtainFreshBeanFactory();
// 准备beanFatcory一些处理器和依赖
this.prepareBeanFactory(beanFactory);
try {
// Register request/session scopes
this.postProcessBeanFactory(beanFactory);
// 下面两个是处理所有实现了BeanFactoryPostProcessor和
// BeanDefinitionRegistryPostProcessor接口
this.invokeBeanFactoryPostProcessors(beanFactory);
this.registerBeanPostProcessors(beanFactory);
// 在Spring容器中初始化一些国际化相关的属性
this.initMessageSource();
// 在Spring容器中初始化事件广播器，事件广播器用于事件的发布
this.initApplicationEventMulticaster();
// 模版方法
this.onRefresh();
// 注册监听器
this.registerListeners();
// 调用preInstantiateSingletons初始化beanFactory所有bean
this.finishBeanFactoryInitialization(beanFactory);
// 生命周期和事件的处理
this.finishRefresh();
} catch (BeansException var5) {
this.logger.warn("Exception encountered during context initialization - cancelling refresh attempt", var5);
this.destroyBeans();
this.cancelRefresh(var5);
throw var5;
}
}
}
6分析下obtainFreshBeanFactory
6.1 看下其中的obtainFreshBeanFactory
protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
// 解析xml，spring是以namespace方式解析，核心类DefaultNamespaceHandlerResolver
this.refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = this.getBeanFactory();
if (this.logger.isDebugEnabled()) {
this.logger.debug("Bean factory for " + this.getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}
6.2 看下其中的refreshBeanFactory，首先判断是否存在beanfactory ,如果存在就销毁bean和benafactory，如果不存在则进行创建；然后就是loadBeanDefinitions，customizeBeanFactory是给子类扩展用的。
protected final void refreshBeanFactory() throws BeansException {
if (this.hasBeanFactory()) {
this.destroyBeans();
this.closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = this.createBeanFactory();
beanFactory.setSerializationId(this.getId());
this.customizeBeanFactory(beanFactory);
this.loadBeanDefinitions(beanFactory);
Object var2 = this.beanFactoryMonitor;
synchronized(this.beanFactoryMonitor) {
this.beanFactory = beanFactory;
}
} catch (IOException var5) {
throw new ApplicationContextException("I/O error parsing bean definition source for " + this.getDisplayName(), var5);
}
}
6.3调用的是XmlWebApplicationContext#loadBeanDefinitions
protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, IOException {
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);
//给xml处理器实例设置环境
beanDefinitionReader.setEnvironment(this.getEnvironment());
//设置资源文件的loader
beanDefinitionReader.setResourceLoader(this);
//xml文件具体处理类
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));
this.initBeanDefinitionReader(beanDefinitionReader);
//beanDefinitionReader实例去处理配置文件
this.loadBeanDefinitions(beanDefinitionReader);
}
// 这里进行定位（找到xml），注册(解析xml)
protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {
String[] configLocations = this.getConfigLocations();
if (configLocations != null) {
String[] arr$ = configLocations;
int len$ = configLocations.length;
for(int i$ = 0; i$ < len$; ++i$) {
String configLocation = arr$[i$];
reader.loadBeanDefinitions(configLocation);
}
}
}
6.4解析xml的核心类DefaultNamespaceHandlerResolver，是在XmlBeanDefinitionReader#registerBeanDefinitions中调用的
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = this.createBeanDefinitionDocumentReader();
documentReader.setEnvironment(this.getEnvironment());
int countBefore = this.getRegistry().getBeanDefinitionCount();
// createReaderContext中调用createDefaultNamespaceHandlerResolver生成
// DefaultNamespaceHandlerResolver
documentReader.registerBeanDefinitions(doc, this.createReaderContext(resource));
return this.getRegistry().getBeanDefinitionCount() - countBefore;
}
7分析下prepareBeanFactory
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// 给beanfactory设置classLoader
beanFactory.setBeanClassLoader(this.getClassLoader());
// 设置表达式解析器
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver());
// 设置配置文件读取器
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, this.getEnvironment()));
// 设置ApplicationContextAwareProcessor
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
// 设置忽视依赖的类
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
// 注册需要依赖的类
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
if (beanFactory.containsBean("loadTimeWeaver")) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
if (!beanFactory.containsLocalBean("environment")) {
beanFactory.registerSingleton("environment", this.getEnvironment());
}
if (!beanFactory.containsLocalBean("systemProperties")) {
beanFactory.registerSingleton("systemProperties", this.getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean("systemEnvironment")) {
beanFactory.registerSingleton("systemEnvironment", this.getEnvironment().getSystemEnvironment());
}
}
8.分析下finishRefresh
protected void finishRefresh() {
// 初始化生命周期处理器，并设置到Spring容器中(LifecycleProcessor)
this.initLifecycleProcessor();
// 调用生命周期处理器的onRefresh方法，这个方法会找出Spring容器中实现了
// LifecycleProcessor接口的类并进行onRefresh方法的调用
this.getLifecycleProcessor().onRefresh();
// 发布ContextRefreshedEvent事件告知对应的ApplicationListener，
// onApplicationEvent会被调用
this.publishEvent((ApplicationEvent)(new ContextRefreshedEvent(this)));
LiveBeansView.registerApplicationContext(this);
}
