Spring:ContextLoaderListener作用

参考资料
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