摘要：
“）；｝Loglogger=LogFactory.getLog；servletContext.log；如果｛logger.info；｝longstartTime=系统。currentTimeMillis（）；尝试｛//创建一个上下文，稍后将对此进行详细解释。#1if｛this.context=createWebApplicationContext；｝如果{ConfigurationWebApplicationContextcwac=this.context；如果（！
web.xml配置文件
<context-param> <param-name>contextConfigLocation</param-name> <param-value> classpath:spring/spring-*.xml </param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener>
ContextLoaderListener上下文加载监听器
/**
* servlet容器创建时创建spring容器
*/
@Override public void contextInitialized(ServletContextEvent event) { initWebApplicationContext(event.getServletContext()); } /** * servlet容器销毁时注销spring容器 */ @Override public void contextDestroyed(ServletContextEvent event) { closeWebApplicationContext(event.getServletContext()); ContextCleanupListener.cleanupAttributes(event.getServletContext()); }
创建spring容器
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!"); } 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 {// 创建上下文，后文详解#1 if (this.context == null) { this.context = createWebApplicationContext(servletContext); } if (this.context instanceof ConfigurableWebApplicationContext) { ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context; if (!cwac.isActive()) { if (cwac.getParent() == null) { ApplicationContext parent = loadParentContext(servletContext); cwac.setParent(parent); }
// 刷新上下文包括解析、注册、实例化bean等，后文详解#2 configureAndRefreshWebApplicationContext(cwac, servletContext); } }
// 将创建好的上下文放到application作用域中 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; } }
书接前文#1
protected WebApplicationContext createWebApplicationContext(ServletContext sc) { // 获得具体的上下文类即XmlWebApplicationContext Class<?> contextClass = determineContextClass(sc); if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) { throw new ApplicationContextException("Custom context class [" + contextClass.getName() + "] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]"); } // 实例化XmlWebApplicationContext对象，构造函数反射 return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass); }
书接前文#2
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) { if (ObjectUtils.identityToString(wac).equals(wac.getId())) { String idParam = sc.getInitParameter(CONTEXT_ID_PARAM); if (idParam != null) { wac.setId(idParam); } else { wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX + ObjectUtils.getDisplayString(sc.getContextPath())); } } wac.setServletContext(sc);
// 获得<context-param>标签中的内容 String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM); if (configLocationParam != null) { wac.setConfigLocation(configLocationParam); }
ConfigurableEnvironment env = wac.getEnvironment(); if (env instanceof ConfigurableWebEnvironment) { ((ConfigurableWebEnvironment) env).initPropertySources(sc, null); } // 检查有没有自定义的上下文 customizeContext(sc, wac);
// 刷新上下文 wac.refresh(); }
接下来是销毁spring容器
public void closeWebApplicationContext(ServletContext servletContext) { servletContext.log("Closing Spring root WebApplicationContext"); try { if (this.context instanceof ConfigurableWebApplicationContext) {
// 这里包括广播shutdown事件，销毁bean，销毁BeanFactory等 ((ConfigurableWebApplicationContext) this.context).close(); } } finally { ClassLoader ccl = Thread.currentThread().getContextClassLoader(); if (ccl == ContextLoader.class.getClassLoader()) { currentContext = null; } else if (ccl != null) { currentContextPerThread.remove(ccl); }
// application作用域中去除上下文 servletContext.removeAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE); if (this.parentContextRef != null) { this.parentContextRef.release(); } } }
static void cleanupAttributes(ServletContext sc) { Enumeration<String> attrNames = sc.getAttributeNames(); while (attrNames.hasMoreElements()) { String attrName = attrNames.nextElement(); if (attrName.startsWith("org.springframework.")) { Object attrValue = sc.getAttribute(attrName);
// 对于实现了DisposableBean接口的bean，容器销毁时执行destroy方法 if (attrValue instanceof DisposableBean) { try { ((DisposableBean) attrValue).destroy(); } catch (Throwable ex) { logger.error("Couldn't invoke destroy method of attribute with name '" + attrName + "'", ex); } } } } }