前言
本文转自“天河聊技术”微信公众号
从本篇文章开始主要介绍spring源码解析相关的spring上下文初始化、bean定义解析、beanFactory创建、初始化、bean定义注册到beanFactory、bean实例化、依赖注入流程中相关的步骤，由于spring源码体系比较庞大，本次主要是跟着程序加载顺序整理，遇到相关关键知识点会单独出来一篇文章，之道这个整个链路顺序解析完毕，后面spring源码合集整理的时候会按照模块进行归类梳理。
正文
本次主要从ContextLoaderListener这个入口进行跟踪源码，进行spring的源码解析。
先简单看下主要的类图
1 bean定义解析相关
2 spring上下文相关
3 beanProcessor相关
beanProcessors对bean的过程管理抽象。
3spring容器加载
跟踪这个方法
org.springframework.web.context.ContextLoaderListener#contextInitialized
servlet监听器初始时会加载初始化web应用程序上下文这个方法
@Overridepublic void contextInitialized(ServletContextEvent event) { initWebApplicationContext(event.getServletContext());}
跟踪这个方法
org.springframework.web.context.ContextLoader#initWebApplicationContext
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {// web上下文是放在servlet上下文中的 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!"); } 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 { // Store context in local instance variable, to guarantee that // it is available on ServletContext shutdown.// 初始化web程序上下文 if (this.context == null) { this.context = createWebApplicationContext(servletContext); } if (this.context instanceof ConfigurableWebApplicationContext) { ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context; if (!cwac.isActive()) { // The context has not yet been refreshed -> provide services such as // setting the parent context, setting the application context id, etc if (cwac.getParent() == null) { // The context instance was injected without an explicit parent -> // determine parent for root web application context, if any. ApplicationContext parent = loadParentContext(servletContext);// 设置上下文的父类 cwac.setParent(parent); }// 配置装载和刷新web上下文 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 ex) { logger.error("Context initialization failed", ex); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex); throw ex; } catch (Error err) { logger.error("Context initialization failed", err); servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err); throw err; } } 从这里可以看出web上下文是存储在servlet上下文中的，key值是
webApplicationContext.ROOT。
开始初始化web程序上下文
if (this.context == null) { this.context = createWebApplicationContext(servletContext);}
跟踪这个方法
org.springframework.web.context.ContextLoader#createWebApplicationContext
创建web应用上下文
protected WebApplicationContext createWebApplicationContext(ServletContext sc) { Class contextClass = determineContextClass(sc);// 如果上下文的类型和ConfigurableWebApplicationContext类型不一致 if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) { throw new ApplicationContextException("Custom context class [" + contextClass.getName() + "] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]"); }// 返回配置上下文对象 return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); }
返回到这个方法
org.springframework.web.context.ContextLoader#initWebApplicationContext
if (cwac.getParent() == null) { 判断上下文是否是活动的，上下文刷新过一次，还没有关闭。
进入到这个方法，配置装载和刷新web上下文
org.springframework.web.context.ContextLoader#configureAndRefreshWebApplicationContext
// 配置和刷新web上下文 protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) { if (ObjectUtils.identityToString(wac).equals(wac.getId())) { // The application context id is still set to its original default value // -> assign a more useful id based on available information// 从配置中获取上下文的id String idParam = sc.getInitParameter(CONTEXT_ID_PARAM); if (idParam != null) { wac.setId(idParam); } else { // Generate default id... 生成上下文id字符串 webApplicationContext:+servlet.getContextPath() wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(sc.getContextPath())); } } wac.setServletContext(sc);// 获取配置文件路径 contextConfigLocation，配置文件可以是多个的，用，换行分开，可以用占位符 String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM); if (configLocationParam != null) { wac.setConfigLocation(configLocationParam); } // The wac environment's #initPropertySources will be called in any case when the context // is refreshed; do it eagerly here to ensure servlet property sources are in place for // use in any post-processing or initialization that occurs below prior to #refresh ConfigurableEnvironment env = wac.getEnvironment(); if (env instanceof ConfigurableWebEnvironment) { ((ConfigurableWebEnvironment) env).initPropertySources(sc, null); }// 加载子类实现的上下文 customizeContext(sc, wac);// 上下文刷新 wac.refresh(); } 获取配置文件路径 contextConfigLocation，配置文件可以是多个的，用，换行分开，可以用占位符
String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
// 加载子类实现的上下文 customizeContext(sc, wac);
org.springframework.web.context.ContextLoader#customizeContext 上下文初始化器找到具体要初始化的上下文类进行初始化
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) { List >> initializerClasses = determineContextInitializerClasses(sc); for (Class > initializerClass : initializerClasses) { Class initializerContextClass = GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class); if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) { throw new ApplicationContextException(String.format( "Could not apply context initializer [%s] since its generic parameter [%s] " + "is not assignable from the type of application context used by this " + "context loader: [%s]", initializerClass.getName(), initializerContextClass.getName(), wac.getClass().getName())); } this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass)); } AnnotationAwareOrderComparator.sort(this.contextInitializers); for (ApplicationContextInitializer initializer : this.contextInitializers) { initializer.initialize(wac); }} 最后
本次介绍到这里，以上内容仅供参考。