SSH集成的java.lang.NullPointerException異常

在完成ssh集成的Struts2層的集成後，啟動Tomcat後，出現了異常：

嚴重: ********** FATAL ERROR STARTING UP STRUTS-SPRING INTEGRATION **********
Looks like the Spring listener was not configured for your web app! 
Nothing will work until WebApplicationContextUtils returns a valid ApplicationContext.
You might need to add the following to web.xml: 
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
十二月 21, 2017 9:28:05 下午 com.opensymphony.xwork2.util.logging.commons.CommonsLogger error
嚴重: Dispatcher initialization failed
java.lang.NullPointerException
at com.opensymphony.xwork2.spring.SpringObjectFactory.getClassInstance(SpringObjectFactory.java:230)
......

在異常界面點SpringObjectFactory.java查看源碼，在

   if (appContext.containsBean(className)) {

上設置斷電，進行Debug，發現appContext的值為null。這是因為，我們在Spring中配置了Struts2，在項目啟動後Struts自動去Spring容器中拿對象，而此時Spring並沒有啟動，所以要讓Spring在伺服器啟動的時候也同時啟動。需要在web.xml中配置

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

該監聽器會在項目啟動的時候同時啟動Spring

在配置完成之後啟動項目，有出現了

IOException parsing XML document from ServletContext resource [/WEB-INF/applicationContext.xml]的異常，很明顯是配置文件的異常，系統沒有載入到applicationContext.xml
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:344)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:304)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:181)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:217)
    at org.springframework.beans.factory.support.AbstractBeanDefinitionReader.loadBeanDefinitions(AbstractBeanDefinitionReader.java:188)
    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:129)
    at org.springframework.context.support.AbstractApplicationContext.obtainFreshBeanFactory(AbstractApplicationContext.java:614)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:515)
    at org.springframework.web.context.ContextLoader.configureAndRefreshWebApplicationContext(ContextLoader.java:443)
    at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:325)
    at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:107)
    at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:5110)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5633)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:145)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1700)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1690)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.FileNotFoundException: Could not open ServletContext resource [/WEB-INF/applicationContext.xml]
    at org.springframework.web.context.support.ServletContextResource.getInputStream(ServletContextResource.java:141)
    at org.springframework.beans.factory.xml.XmlBeanDefinitionReader.loadBeanDefinitions(XmlBeanDefinitionReader.java:330)
    ... 21 more

我們需要在web.xml中配置

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

這些內容告訴了listener applicationContext.xml的載入路徑