在使用Spring MVC的时候，标准的配置是如下这样的：

1.ContextLoaderListener配置：

<!-- Spring读取Spring的配置文件 -->
    <context-param>
        <!-- 名称 -->
        <param-name>contextConfigLocation</param-name>
        <!-- 文件的位置 -->
        <param-value>classpath:application-context.xml</param-value>
    </context-param>
<context-param>
    <param-name>webAppRootKey</param-name>
    <param-value>meipian</param-value>
</context-param>
    <!-- Spring 的监听器配置 -->
    <listener>
        <!-- 在Spring-web包下 context -->
        <listener-class>org.springframework.web.context.ContextLoaderListener
        </listener-class>
    </listener>复制代码

2.DispatcherServlet的配置：

<servlet>
        <servlet-name>meipian</servlet-name>
        <!-- 配置SpringMVC核心控制器 -->
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:springmvc.xml</param-value>
        </init-param>
    </servlet>
        <servlet-mapping>
        <servlet-name>meipian</servlet-name>
        <url-pattern>/*</url-pattern>
    </servlet-mapping>复制代码

ContextLoaderListener监听器的作用就是启动Web容器时，自动装配ApplicationContext的配置信息。因为它实现了ServletContextListener这个接口，在web.xml配置这个监听器，启动容器时，就会执行其实现的方法。Spring
MVC的使用的容器是WebApplicationContext。那么他和ContextLoaderListener所初始化的ApplicationContext有什么关系呢？

可以从DispatcherServlet的初始化过程说起：DispatcherServlet拦截了所有的请求，所以访问任何一个接口都会初始化DispatcherServlet对象。

初始化DispatcherServlet只是做了一个很简单的事：

public DispatcherServlet() { super();
        setDispatchOptionsRequest(true);
    }复制代码

其父类FrameworkServlet初始化什么也没有:复制代码

public FrameworkServlet() {
    }复制代码

然后是Tomcat会调用DispatcherServlet的初始化方法，在Servlet的生命周期中，仅执行一次init（）方法。它是在服务器上封装Servlet时执行的。 Servlet。任何有多少可以访问的Servlet，都不会重复执行init（）。别问我为什么会调用init方法，这是servlet的规范。DispatcherServlet的init方法是在父类FrameworkServlet的父类HttpServlet中实现的：

@Override
    public final void init() throws ServletException { if (logger.isDebugEnabled()) {
            logger.debug("Initializing servlet '" + getServletName() + "'");
        } // Set bean properties from init parameters. try {
            PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
            BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
            ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
            bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
            initBeanWrapper(bw);
            bw.setPropertyValues(pvs, true);
        } catch (BeansException ex) {
            logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex); throw ex;
        } // Let subclasses do whatever initialization they like. initServletBean(); if (logger.isDebugEnabled()) {
            logger.debug("Servlet '" + getServletName() + "' configured successfully");
        }
    }复制代码

会调用DispatcherServlet的initServletBean（）方法就是初始化WebApplicationContext的方法。这个方法在其子类FrameServlet方法中实现：

@Override
    protected final void initServletBean() throws ServletException {
        getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'"); if (this.logger.isInfoEnabled()) { this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
        }
        long startTime = System.currentTimeMillis(); try { this.webApplicationContext = initWebApplicationContext(); //初始化WebApplicationContext对象 initFrameworkServlet();
        } catch (ServletException ex) { this.logger.error("Context initialization failed", ex); throw ex;
        } catch (RuntimeException ex) { this.logger.error("Context initialization failed", ex); throw ex;
        } if (this.logger.isInfoEnabled()) {
            long elapsedTime = System.currentTimeMillis() - startTime; this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
                    elapsedTime + " ms");
        }
    }复制代码

initWebApplicationContext方法如下所示：

protected WebApplicationContext initWebApplicationContext() {
        WebApplicationContext rootContext =
                WebApplicationContextUtils.getWebApplicationContext(getServletContext());
        WebApplicationContext wac = null; if (this.webApplicationContext != null) { // A context instance was injected at construction time -> use it wac = this.webApplicationContext; if (wac instanceof ConfigurableWebApplicationContext) {
                ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac; 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 -> set // the root application context (if any; may be null) as the parent cwac.setParent(rootContext);
                    }
                    configureAndRefreshWebApplicationContext(cwac);
                }
            }
        } if (wac == null) { // No context instance was injected at construction time -> see if one // has been registered in the servlet context. If one exists, it is assumed // that the parent context (if any) has already been set and that the // user has performed any initialization such as setting the context id wac = findWebApplicationContext();
        } if (wac == null) { // No context instance is defined for this servlet -> create a local one wac = createWebApplicationContext(rootContext);
        } if (!this.refreshEventReceived) { // Either the context is not a ConfigurableApplicationContext with refresh // support or the context injected at construction time had already been // refreshed -> trigger initial onRefresh manually here. onRefresh(wac);
        } if (this.publishContext) { // Publish the context as a servlet context attribute. String attrName = getServletContextAttributeName();
            getServletContext().setAttribute(attrName, wac); if (this.logger.isDebugEnabled()) { this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() + "' as ServletContext attribute with name [" + attrName + "]");
            }
        } return wac;
    }复制代码

会默认走到createWebApplicationContext方法:复制代码

protected WebApplicationContext createWebApplicationContext(ApplicationContext parent) {
        Class<?> contextClass = getContextClass(); if (this.logger.isDebugEnabled()) { this.logger.debug("Servlet with name '" + getServletName() + "' will try to create custom WebApplicationContext context of class '" +
                    contextClass.getName() + "'" + ", using parent context [" + parent + "]");
        } if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) { throw new ApplicationContextException( "Fatal initialization error in servlet with name '" + getServletName() + "': custom WebApplicationContext class [" + contextClass.getName() + "] is not of type ConfigurableWebApplicationContext");
        }
        ConfigurableWebApplicationContext wac =
                (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);

        wac.setEnvironment(getEnvironment());
        wac.setParent(parent);
        wac.setConfigLocation(getContextConfigLocation());

        configureAndRefreshWebApplicationContext(wac); return wac;
    }复制代码

在有contexloaderListener的情况下，父母是空的。
在有contexloaderListener的情况下，发现父母不是空的。

而且在Spring MVC的配置中，如果您将服务的配置与mvc的配置写在一起，有没有contexloaderListener无所谓的。

这就说明了contexloaderListener作用是什么了。