事情是这样子的,看到一个关于springmvc源码解读的文章,他说tomcat是如何初始化ApplicationContext容器的,

springMVC源码分析--容器初始化（一）ContextLoaderListener

 这个图,写的非常好

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
      version="3.0">

	<!-- The definition of the Root Spring Container shared by all Servlets and Filters -->
	<context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>/WEB-INF/spring/root-context.xml</param-value>
	</context-param>
	
	<!-- Creates the Spring Container shared by all Servlets and Filters -->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>

	<filter>
		<filter-name>csrfFilter</filter-name>
		<filter-class>org.springframework.web.filter.DelegatingFilterProxy</filter-class>
		<async-supported>true</async-supported>
	</filter>
	<filter-mapping>
		<filter-name>csrfFilter</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
    
	<!-- Processes application requests -->
	<servlet>
		<servlet-name>appServlet</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
		<init-param>
			<param-name>contextConfigLocation</param-name>
			<param-value>/WEB-INF/spring/appServlet/servlet-context.xml</param-value>
		</init-param>
		<load-on-startup>1</load-on-startup>
		<async-supported>true</async-supported>
	</servlet>
		
	<servlet-mapping>
		<servlet-name>appServlet</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>

	<!-- Disables Servlet Container welcome file handling. Needed for compatibility with Servlet 3.0 and Tomcat 7.0 -->
	<welcome-file-list>
		<welcome-file></welcome-file>
	</welcome-file-list>	

</web-app>

　　这里主要表达的是添加了这个listener,那么这个listenter是tomcat加载的流程中加载的,

以前我是tomcat源码专家呢,那么在哪里加载的这个listner呢?那么就捋捋

这个是<listener>标签,那么那查看 WebRuleSet 类

在

        digester.addCallMethod(prefix + "web-app/listener/listener-class",
                               "addApplicationListener", 0);

看到.这个是对于StanderContext对象进行添加, addApplicationListener

那么就要定位到StanderContext .addApplicationListener方法

   类名 public class StandardContext
 public void addApplicationListener(String listener) {

        synchronized (applicationListeners) {
            String results[] =new String[applicationListeners.length + 1];
            for (int i = 0; i < applicationListeners.length; i++) {
                if (listener.equals(applicationListeners[i]))
                    return;
                results[i] = applicationListeners[i];
            }
            results[applicationListeners.length] = listener;
            applicationListeners = results;
        }
        fireContainerEvent("addApplicationListener", listener);

        // FIXME - add instance if already started?

    }

接着看调用在哪里 StandandContext 3211 行

        // Send application start events

        if (debug >= 1)
            log("Sending application start events");

        setApplicationListeners(results);
        Object instances[] = getApplicationListeners();
        if (instances == null)
            return (ok);
        ServletContextEvent event =
          new ServletContextEvent(getServletContext());
        for (int i = 0; i < instances.length; i++) {
            if (instances[i] == null)
                continue;
            if (!(instances[i] instanceof ServletContextListener))
                continue;
            ServletContextListener listener =
                (ServletContextListener) instances[i];
            try {
                fireContainerEvent("beforeContextInitialized", listener);
                listener.contextInitialized(event);
                fireContainerEvent("afterContextInitialized", listener);
            } catch (Throwable t) {
                fireContainerEvent("afterContextInitialized", listener);
                log(sm.getString("standardContext.listenerStart",
                                 instances[i].getClass().getName()), t);
                ok = false;
            }
        }
        return (ok);

这就连上了,调用了listener.contextInitailized(event)方法

    @Override
    public void contextInitialized(ServletContextEvent event) {
        initWebApplicationContext(event.getServletContext());
    }

initWebApplicationContext  方法在他的父类

ContextLoader 上面

    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 {
            // Store context in local instance variable, to guarantee that
            // it is available on ServletContext shutdown.
            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);
                        cwac.setParent(parent);
                    }
                    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;
        }
    }

以上标记为黄色的行就对应了,我张贴的逻辑图的过程,

看了的东西,真是记不住, 看到别人的分析,确实比我强呢,所以最近就加强看springmvc的东西吧

标签：学习指南,web,servletContext,springframework,listener,context,logger,WebApplicationCo
来源： https://www.cnblogs.com/zytcomeon/p/15703541.html