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本次主要介紹springmvc配置解析,更多源碼解析文章請關注「天河聊技術」微信公衆號。spring
springmvc配置解析微信
本次介紹org.springframework.web.context.ContextLoaderListener初始化,進入到這個方法org.springframework.web.context.ContextLoaderListener#contextInitialized,監聽器收到一個servletContext上下文初始化完畢的事件後初始化WebApplicationContext,進入到這個方法org.springframework.web.context.ContextLoader#initWebApplicationContextmvc
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) { //從servletContext中獲取綁定key值是org.springframework.context.ApplicationContext.WebApplicationContext.ROOT的webApplicationContext對象 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 將上下文存儲在本地實例變量中,以保證這一點 // it is available on ServletContext shutdown.它在ServletContext關閉時可用。 if (this.context == null) { //建立web上下文 -> 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 上下文還沒有刷新—>提供瞭如下服務 // setting the parent context, setting the application context id, etc 設置父上下文、設置應用程序上下文id等等 if (cwac.getParent() == null) { // The context instance was injected without an explicit parent -> 上下文實例在沒有顯式父>的狀況下被注入 // determine parent for root web application context, if any.肯定根web應用程序上下文的父級(若是有的話)。 //-> ApplicationContext parent = loadParentContext(servletContext); cwac.setParent(parent); } // 配置和刷新web上下文 -> configureAndRefreshWebApplicationContext(cwac, servletContext); } } // web上下文綁定到servlet上下文中,key=org.springframework.web.context.WebApplicationContext.ROOT 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; } }
進入到這個方法org.springframework.web.context.ContextLoader#createWebApplicationContextapp
protected WebApplicationContext createWebApplicationContext(ServletContext sc) { //找到web上下文初始化類 -> Class<?> contextClass = determineContextClass(sc); if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) { throw new ApplicationContextException("Custom context class [" + contextClass.getName() + "] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]"); } //初始化web上下文 return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); }
進入到這個方法org.springframework.web.context.ContextLoader#determineContextClasside
protected Class<?> determineContextClass(ServletContext servletContext) { //從servlet上下文獲取contextClass屬性值,指定web上下文的類 String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM); if (contextClassName != null) { try { return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader()); } catch (ClassNotFoundException ex) { throw new ApplicationContextException( "Failed to load custom context class [" + contextClassName + "]", ex); } } else { // 若是servlet上下文沒有配置這個屬性值就從ContextLoader.properties這個配置文件中加載 -> contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName()); try { return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader()); } catch (ClassNotFoundException ex) { throw new ApplicationContextException( "Failed to load default context class [" + contextClassName + "]", ex); } } }
找到這裏post
static { // Load default strategy implementations from properties file. // This is currently strictly internal and not meant to be customized // by application developers. try { // 加載web上下文默認初始化類org.springframework.web.context.support.XmlWebApplicationContext從ContextLoader.properties這個配置文件 ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class); defaultStrategies = PropertiesLoaderUtils.loadProperties(resource); } catch (IOException ex) { throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage()); } }
往上返回到這個方法org.springframework.web.context.ContextLoader#loadParentContextthis
protected ApplicationContext loadParentContext(ServletContext servletContext) { ApplicationContext parentContext = null; //從servlet上下文獲取locatorFactorySelector參數值 String locatorFactorySelector = servletContext.getInitParameter(LOCATOR_FACTORY_SELECTOR_PARAM); //從servlet上下文獲取parentContextKey參數值 String parentContextKey = servletContext.getInitParameter(LOCATOR_FACTORY_KEY_PARAM); if (parentContextKey != null) { // locatorFactorySelector may be null, indicating the default "classpath*:beanRefContext.xml" locatorFactorySelector能夠是null,表示默認的「classpath*:beanRefContext.xml」 BeanFactoryLocator locator = ContextSingletonBeanFactoryLocator.getInstance(locatorFactorySelector); Log logger = LogFactory.getLog(ContextLoader.class); if (logger.isDebugEnabled()) { logger.debug("Getting parent context definition: using parent context key of '" + parentContextKey + "' with BeanFactoryLocator"); } this.parentContextRef = locator.useBeanFactory(parentContextKey); parentContext = (ApplicationContext) this.parentContextRef.getFactory(); } return parentContext; }
往上返回進入到這個方法org.springframework.web.context.ContextLoader#configureAndRefreshWebApplicationContextspa
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 應用程序上下文id仍然設置爲其原始默認值 // -> assign a more useful id based on available information ->根據可用信息分配一個更有用的id // 從servlet上下文中獲取contextId參數值 String idParam = sc.getInitParameter(CONTEXT_ID_PARAM); if (idParam != null) { wac.setId(idParam); } else { // Generate default id... wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(sc.getContextPath())); } } wac.setServletContext(sc); //從servlet上下文獲取contextConfigLocation參數值 spring上下文的配置文件 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 wac環境的#initPropertySources將在上下文中的任何狀況下被調用 // is refreshed; do it eagerly here to ensure servlet property sources are in place for 刷新;在這裏急切地確保servlet屬性源的位置是合適的嗎 // use in any post-processing or initialization that occurs below prior to #refresh 用於任何後處理或初始化中,發生在#刷新以前 ConfigurableEnvironment env = wac.getEnvironment(); if (env instanceof ConfigurableWebEnvironment) { // 初始化servlet參數 -> ((ConfigurableWebEnvironment) env).initPropertySources(sc, null); } //定製化spring上下文 -> customizeContext(sc, wac); //刷新spring上下文,這裏在以前的spring源碼解析中有詳細介紹 wac.refresh(); }
進入到這個方法org.springframework.web.context.ContextLoader#customizeContextdebug
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) { //找到上下文初始化類 -> List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> initializerClasses = determineContextInitializerClasses(sc); //判斷上下文初始化類是不是ConfigurableWebApplicationContext類型 for (Class<ApplicationContextInitializer<ConfigurableApplicationContext>> 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())); } // 初始化上下文初始化類 this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass)); } AnnotationAwareOrderComparator.sort(this.contextInitializers); for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) { // 調用初始化器的初始化方法,初始化器能夠本身實現 initializer.initialize(wac); } }
進入到這個方法org.springframework.web.context.ContextLoader#determineContextInitializerClasses
protected List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> determineContextInitializerClasses(ServletContext servletContext) { List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> classes = new ArrayList<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>>(); //從servlet上下文中獲取globalInitializerClasses參數值 String globalClassNames = servletContext.getInitParameter(GLOBAL_INITIALIZER_CLASSES_PARAM); if (globalClassNames != null) { for (String className : StringUtils.tokenizeToStringArray(globalClassNames, INIT_PARAM_DELIMITERS)) { //加載初始化類,多個類用,或者;分開 classes.add(loadInitializerClass(className)); } } //從servlet上下文獲取contextInitializerClasses參數值 String localClassNames = servletContext.getInitParameter(CONTEXT_INITIALIZER_CLASSES_PARAM); if (localClassNames != null) { for (String className : StringUtils.tokenizeToStringArray(localClassNames, INIT_PARAM_DELIMITERS)) { //加載初始化類,多個類用,或者;分開 classes.add(loadInitializerClass(className)); } } return classes; }
往上返回到這個方法org.springframework.web.context.ContextLoaderListener#contextInitialized
說到最後
本次源碼解析僅表明我的觀點,僅供參考。