Spring框架学习[Web环境中Spring的启动过程] - JAVA

的无参构造方法创建实例对象 ConfigurableWebApplicationContext wac = (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); //如果Servlet大版本是2，并且小版本号小于5，即是Servlet2.4以下标准 if (sc.getMajorVersion() == 2 && sc.getMinorVersion() < 5) { //获取Servlet上下文名称 String servletContextName = sc.getServletContextName(); //为创建的Web应用上下文设置唯一的Id标识 wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(servletContextName)); } //Servlet2.5标准 else { try { //调用Servlet上下文对象中getContextPath()方法 String contextPath = (String) ServletContext.class.getMethod("getContextPath").invoke(sc); //为Web上下文设置唯一Id标识 wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(contextPath)); } catch (Exception ex) { throw new IllegalStateException("Failed to invoke Servlet 2.5 getContextPath method", ex); } } //设置Web上下文的父级上下文 wac.setParent(parent); //设置Web上下文的Servlet上下文 wac.setServletContext(sc); //Servlet上下文从web.xml文件中获取配置的contextConfigLocation参数，并 //将其作为Spring Web上下文配置资源的值 wac.setConfigLocation(sc.getInitParameter(CONFIG_LOCATION_PARAM)); //调用用户自定义的设置应用上下文方法 customizeContext(sc, wac); //刷新Spring Web容器，启动载入Spring配置资源的过程 wac.refresh(); return wac; } //根据给定的Servlet上下文，获取Spring Web上下文的实现类//XmlWebApplicationContext或者用户自定义的Spring Web应用上下文 protected Class determineContextClass(ServletContext servletContext) { //Servlet上下文从web.xml中获取配置的contextClass参数值 String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM); //如果web.xml中额外配置了contextClass参数值 if (contextClassName != null) { try { //使用JDK反射机制，实例化指定名称的contextClass类对象 return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader()); } catch (ClassNotFoundException ex) { throw new ApplicationContextException( "Failed to load custom context class [" + contextClassName + "]", ex); } } //如果web.xml中没有配置contextClass参数值 else { //获取Spring中默认的Web应用上下文策略，即XmlWebApplicationContext contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName()); try { //使用JDK反射机制，创建Spring Web应用上下文默认策略类对象 return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader()); } catch (ClassNotFoundException ex) { throw new ApplicationContextException( "Failed to load default context class [" + contextClassName + "]", ex); } } }

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</div>//初始化Spring根上下文public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {//ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE = WebApplicationContext.class.getName() + ".ROOT";//判断在Servlet上下文中Spring Web应用给根上下文是否已经存在		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!");		}		//记录日志		Log logger = LogFactory.getLog(ContextLoader.class);		servletContext.log("Initializing Spring root WebApplicationContext");		if (logger.isInfoEnabled()) {			logger.info("Root WebApplicationContext: initialization started");		}		//获取当前系统时间		long startTime = System.currentTimeMillis();		try {			//如果当前Web根容器有父容器，则获取父容器			ApplicationContext parent = loadParentContext(servletContext);			//根据给定Servlet容器和父容器创建Web应用容器，并且所创建的Web应用//容器实例对象存储在本地变量中，以确保当Servlet容器关闭时该容器可用			this.context = createWebApplicationContext(servletContext, parent);		//将创建的Web应用上下文设置到Servlet上下文的应用根容器属性中	servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);			//获取当前线程的容器类加载器			ClassLoader ccl = Thread.currentThread().getContextClassLoader();			//如果当前线程的容器类加载器是ContextLoader类，则当前上下文就设置为//创建的Web应用上下文			if (ccl == ContextLoader.class.getClassLoader()) {				currentContext = this.context;			}			//如果当前线程的容器类加载器不为null，则将创建的web应用上下文和其类//加载器缓存在容器类加载器—>Web应用上下文Map集合中			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: initializ</span>
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Spring框架学习[Web环境中Spring的启动过程](四)