spring ContextLoaderListener的作用

1 Spring之ContextLoaderListener的作用 
http://lei2006.blog.sohu.com/116206469.html  

使用spring除了添加必要的jar包,另外在web.xml一定要加上启动spring的监听器,这样配置在xml文件中的bean才会初始化 

如你在web.xml这样作了配置:(web.xml 2.4) 

 <listener>
         <listener-class>
             org.springframework.web.context.ContextLoaderListener
         </listener-class>
     </listener>

它会默认查找位于:WEB-INF/下的是否有一个文件名称为:applicationContext.xml 
如果没有就会报错: 
严重: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener 
org.springframework.beans.factory.BeanDefinitionStoreException: IOException parsing XML document from ServletContext resource [/WEB-INF/applicationContext.xml]; nested exception is java.io.FileNotFoundException: Could not open ServletContext resource [/WEB-INF/applicationContext.xml] 
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:341)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:302)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:174)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:209)
at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:180)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:125)
at org.springframework.web.context.support.XmlWebApplicationContext.loadBeanDefinitions(XmlWebApplicationContext.java:94)
at org.springframework.context.support.AbstractRefreshableApplicationContext.refreshBeanFactory(AbstractRefreshableApplicationContext.java:131)
at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:509)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:427) 
at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:294) 
at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:215) 
at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47) 
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4521) 
at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:5004) 
at org.apache.catalina.core.StandardContext$1.call(StandardContext.java:4999) 
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303) 
at java.util.concurrent.FutureTask.run(FutureTask.java:138) 
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) 
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) 
at java.lang.Thread.run(Thread.java:619) 
Caused by: java.io.FileNotFoundException: Could not open ServletContext resource [/WEB-INF/applicationContext.xml] 
at org.springframework.web.context.support.ServletContextResource.getInputStream(ServletContextResource.java:117)
at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:328)
... 20 more  
但在很多项目中可能会把配置文件集中管理,常见位置在:classpath下面,这样的话,你要在web.xml中在配置另外一个节点名称: 

 <context-param>
         <param-name>
             contextConfigLocation
         </param-name>
         <param-value>
             classpath*:applicationContext.xml
         </param-value>
     </context-param>

常见可能是这样: /WEB-INF/classes/applicationContext-*.xml  
总之它是使用spring必须要配置的元素,一定不要少了