漯河公司做网站,省级建筑信息平台,什么是网络营销?请举几个例子说明,中卫中医肿瘤医院平面设计师Spring MVC源码——Root WebApplicationContext 打算开始读一些框架的源码,先拿 Spring MVC 练练手,欢迎点击这里访问我的源码注释, SpringMVC官方文档一开始就给出了这样的两段示例: WebApplicationInitializer示例: public class MyWebApplicationInitializer implements Web… Spring MVC源码——Root WebApplicationContext 打算开始读一些框架的源码,先拿 Spring MVC 练练手,欢迎点击这里访问我的源码注释, SpringMVC官方文档一开始就给出了这样的两段示例: WebApplicationInitializer示例: public class MyWebApplicationInitializer implements WebApplicationInitializer {Overridepublic void onStartup(ServletContext servletCxt) {// Load Spring web application configurationAnnotationConfigWebApplicationContext ac new AnnotationConfigWebApplicationContext();ac.register(AppConfig.class);ac.refresh();// Create and register the DispatcherServletDispatcherServlet servlet new DispatcherServlet(ac);ServletRegistration.Dynamic registration servletCxt.addServlet(app, servlet);registration.setLoadOnStartup(1);registration.addMapping(/app/*);}
} web.xml 示例: web-applistenerlistener-classorg.springframework.web.context.ContextLoaderListener/listener-class/listenercontext-paramparam-namecontextConfigLocation/param-nameparam-value/WEB-INF/app-context.xml/param-value/context-paramservletservlet-nameapp/servlet-nameservlet-classorg.springframework.web.servlet.DispatcherServlet/servlet-classinit-paramparam-namecontextConfigLocation/param-nameparam-value/param-value/init-paramload-on-startup1/load-on-startup/servletservlet-mappingservlet-nameapp/servlet-nameurl-pattern/app/*/url-pattern/servlet-mapping/web-app 我们按照 web.xml 中的实例来看一下 Spring MVC 初始化过程. 上下文层次结构 Spring MVC 的上下文有如下这样的层级: 图中的 Servlet WebApplicationContext 是与 DispatcherServlet 绑定的上下文, 其中还有 controllers、ViewResolver、HandlerMapping 等组件. Root WebApplicationContext 不是必须的上下文, 在需要时,可以用来在多个 DispatcherServlet 间共享一些 bean. Root WebApplicationContext 初始化和销毁 ContextLoaderListener web.xml 中配置的 ContextLoaderListener 用于启动和终止 Spring 的 root WebApplicationContext. ContextLoaderListener public class ContextLoaderListener extends ContextLoader implements ServletContextListener {public ContextLoaderListener() {}public ContextLoaderListener(WebApplicationContext context) {super(context);}/*** Initialize the root web application context.* Servlet 上下文初始化,调用父类的方法初始化 WebApplicationContext*/Overridepublic void contextInitialized(ServletContextEvent event) {initWebApplicationContext(event.getServletContext());}/*** Close the root web application context.* Servlet 上下文被销毁,调用父类的方法销毁 WebApplicationContext*/Overridepublic void contextDestroyed(ServletContextEvent event) {closeWebApplicationContext(event.getServletContext());// 销毁 ServletContext 上实现了 DisposableBean 的属性并移除他们ContextCleanupListener.cleanupAttributes(event.getServletContext());}
} ContextLoaderListener 直接调用了父类 ContextLoader 的方法来初始化和销毁上下文. ContextLoaderListener 在创建上下文时,会尝试读取 contextClass context-param 来指定上下文的类型,被指定的类需要实现 ConfigurableWebApplicationContext 接口. 如果没有获取到,默认会使用 WebApplicationContext. 初始化上下文时,会尝试读取 contextConfigLocation context-param, 作为 xml 文件的路径. 初始化上下文 initWebApplicationContext() 方法如下: public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {// 检查有没有绑定上下文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!);}servletContext.log(Initializing Spring root WebApplicationContext);Log logger LogFactory.getLog(ContextLoader.class);if (logger.isInfoEnabled()) {logger.info(Root WebApplicationContext: initialization started);}// 初始化开始时间long startTime System.currentTimeMillis();try {// Store context in local instance variable, to guarantee that// it is available on ServletContext shutdown.// 保存上下文到本地实例变量中保证上细纹能在 ServletContext 关闭时访问到if (this.context null) {// 创建上下文this.context createWebApplicationContext(servletContext);}if (this.context instanceof ConfigurableWebApplicationContext) {// 如果上下文实现了 ConfigurableWebApplicationContextConfigurableWebApplicationContext cwac (ConfigurableWebApplicationContext) this.context;if (!cwac.isActive()) {// 上下文还没有刷新设置 父上下文如果能找到并且刷新// The context has not yet been refreshed - provide services such as// setting the parent context, setting the application context id, etcif (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);cwac.setParent(parent);}// 设置和刷新上下文configureAndRefreshWebApplicationContext(cwac, servletContext);}}// 将上下文绑定到 servletContext 的属性上servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);// 获取当前线程的上下文类加载器ClassLoader ccl Thread.currentThread().getContextClassLoader();if (ccl ContextLoader.class.getClassLoader()) {currentContext this.context;}else if (ccl ! null) {// 如果有线程上下文类加载器而且不是 ContextLoader 本身的类加载器放入到 currentContextPerThread 中。这是一个 static 的域currentContextPerThread.put(ccl, this.context);}if (logger.isInfoEnabled()) {long elapsedTime System.currentTimeMillis() - startTime;logger.info(Root WebApplicationContext initialized in elapsedTime ms);}return this.context;}catch (RuntimeException | Error ex) {// 发生异常, 把异常绑定到上下文对应的属性上,之后不会再进行初始化logger.error(Context initialization failed, ex);servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);throw ex;}
} initWebApplicationContext() 方法调用了 createWebApplicationContext() 方法来创建上下文;调用了 configureAndRefreshWebApplicationContext() 来对实现了 ConfigurableWebApplicationContext 接口的上下文做初始化. createWebApplicationContext() 会调用 determineContextClass() 来获取上下文类型的 Class 对象. protected WebApplicationContext createWebApplicationContext(ServletContext sc) {// 获取上下文类型Class? contextClass determineContextClass(sc);// 检查是否实现了 ConfigurableWebApplicationContextif (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {throw new ApplicationContextException(Custom context class [ contextClass.getName() ] is not of type [ ConfigurableWebApplicationContext.class.getName() ]);}// 实例化return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
}protected Class? determineContextClass(ServletContext servletContext) {// 获取 serveltContext 的 contextClass 初始化参数。String contextClassName servletContext.getInitParameter(CONTEXT_CLASS_PARAM);if (contextClassName ! null) {// 指定过上下文类型加载类try {return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader());}catch (ClassNotFoundException ex) {throw new ApplicationContextException(Failed to load custom context class [ contextClassName ], ex);}}else {// 去默认策略里获取默认的上下文类型名称contextClassName defaultStrategies.getProperty(WebApplicationContext.class.getName());try {// 加载类return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader());}catch (ClassNotFoundException ex) {throw new ApplicationContextException(Failed to load default context class [ contextClassName ], ex);}}
} configureAndRefreshWebApplicationContext() 方法. protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {// 用可以获取到的信息获取一个更有意义的上下文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// 获取 ServletContext 的 contextId 初始化参数。String idParam sc.getInitParameter(CONTEXT_ID_PARAM);if (idParam ! null) {wac.setId(idParam);}else {// Generate default id...// 生成默认 idwac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX ObjectUtils.getDisplayString(sc.getContextPath()));}}// 设置 servletContext 属性wac.setServletContext(sc);// 设置配置文件路径String configLocationParam sc.getInitParameter(CONFIG_LOCATION_PARAM);if (configLocationParam ! null) {wac.setConfigLocation(configLocationParam);}// The wac environments #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// 初始化属性源 确保 servlet 属性源到位并能够在任何 refresh 之前的后期处理和初始化中使用ConfigurableEnvironment env wac.getEnvironment();if (env instanceof ConfigurableWebEnvironment) {((ConfigurableWebEnvironment) env).initPropertySources(sc, null);}// 在设置了配置文件之后上下文刷新之前自定义上下文customizeContext(sc, wac);wac.refresh();
}protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {// 根据 ServletContext 的 contextInitializerClasses 和 globalInitializerClasses 初始化参数 加载 ApplicationContextInitializer 的 classListClassApplicationContextInitializerConfigurableApplicationContext initializerClasses determineContextInitializerClasses(sc);for (ClassApplicationContextInitializerConfigurableApplicationContext initializerClass : initializerClasses) {// 获取范型参数类型Class? initializerContextClass GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);// 检查 Initializer 是否适用于当前上下文对象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()));}// 创建 Initializer 实例并添加到 contextInitializersthis.contextInitializers.add(BeanUtils.instantiateClass(initializerClass));}// 根据 org.springframework.core.Ordered 和 org.springframework.core.annotation.Order 排序如果没有实现或注解会被排到最后AnnotationAwareOrderComparator.sort(this.contextInitializers);// 执行每个 initializer 的 initialize() 方法for (ApplicationContextInitializerConfigurableApplicationContext initializer : this.contextInitializers) {initializer.initialize(wac);}
} 销毁上下文 closeWebApplicationContext() 方法如下: public void closeWebApplicationContext(ServletContext servletContext) {servletContext.log(Closing Spring root WebApplicationContext);try {// 如果 context 是 ConfigurableWebApplicationContext 调用 close() 方法if (this.context instanceof ConfigurableWebApplicationContext) {((ConfigurableWebApplicationContext) this.context).close();}}finally {ClassLoader ccl Thread.currentThread().getContextClassLoader();if (ccl ContextLoader.class.getClassLoader()) {currentContext null;}else if (ccl ! null) {currentContextPerThread.remove(ccl);}// 移除 servletContext 中的 context 属性servletContext.removeAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);}
} Servlet 3.0 中初始化 Servlet 3.0 中可以通过 ServletContext 的 addlistener() 方法来添加监听器.因此可以先把 Spring 容器先创建好,再传给 ContextLoaderListener 的构造器.这里就不自己写例子了,选了单元测试中的 ContextLoaderTests.testContextLoaderListenerWithDefaultContext() 方法: public void testContextLoaderListenerWithDefaultContext() {MockServletContext sc new MockServletContext();sc.addInitParameter(ContextLoader.CONFIG_LOCATION_PARAM,/org/springframework/web/context/WEB-INF/applicationContext.xml /org/springframework/web/context/WEB-INF/context-addition.xml);ServletContextListener listener new ContextLoaderListener();ServletContextEvent event new ServletContextEvent(sc);listener.contextInitialized(event);String contextAttr WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE;WebApplicationContext context (WebApplicationContext) sc.getAttribute(contextAttr);assertTrue(Correct WebApplicationContext exposed in ServletContext, context instanceof XmlWebApplicationContext);assertTrue(WebApplicationContextUtils.getRequiredWebApplicationContext(sc) instanceof XmlWebApplicationContext);LifecycleBean lb (LifecycleBean) context.getBean(lifecycle);assertTrue(Has father, context.containsBean(father));assertTrue(Has rod, context.containsBean(rod));assertTrue(Has kerry, context.containsBean(kerry));assertTrue(Not destroyed, !lb.isDestroyed());assertFalse(context.containsBean(beans1.bean1));assertFalse(context.containsBean(beans1.bean2));listener.contextDestroyed(event);assertTrue(Destroyed, lb.isDestroyed());assertNull(sc.getAttribute(contextAttr));assertNull(WebApplicationContextUtils.getWebApplicationContext(sc));
} 转自https://www.cnblogs.com/FJH1994/p/10798028.html 转载于:https://www.cnblogs.com/hujunzheng/p/10819473.html
