当我尝试从沙箱中单独运行人员配备示例时，出现以下错误。
错误如下：
You might need to add the following to web.xml:
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
Jun 17, 2013 7:17:39 AM org.apache.catalina.core.StandardContext filterStart
SEVERE: Exception starting filter struts2
java.lang.NullPointerException
at com.opensymphony.xwork2.spring.SpringObjectFactory.getClassInstance(SpringObjectFactory.java:188)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyResultType(XmlConfigurationProvider.java:479)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addResultTypes(XmlConfigurationProvider.java:450)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:407)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:239)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:152)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:395)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452)
at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:295)
at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:422)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:115)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4072)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4726)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
at org.apache.catalina.core.StandardService.start(StandardService.java:525)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
网页.xml：
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
<init-param>
<param-name>actionPackages</param-name>
<param-value>manning</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>anotherServlet</servlet-name>
<servlet-class>manning.servlet.AnotherServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>anotherServlet</servlet-name>
<url-pattern>/anotherServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
</welcome-file-list>
</web-app>
struts.xml
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<!--
For the purposes of the book, we will leave devMode set to true. This
allows several things to occur including provision of debugging level information
on error pages as well as reloading of various resources with each request.
-->
<constant name="struts.devMode" value="true" />
<!--
You can define packages directly in this file, but its probably best
to modularize the configuration files with separate xml files for each
package. Ulitmately its all the same because the include element, seen
below, pulls the included configuration document directly in to the
primary document. The only thing to consider is that a referenced
element must have been declared above the referring element.
-->
<!--
This is the menu action that will allow the reader to see the different
samples actions from the different chapters in a menu format. We declare
it here, in the root namespace, because its not really related to any of the
specific examples or chapters, its just a kind of utility for the whole
application.
-->
<package name="default" namespace="/" extends="struts-default">
<action name="Menu">
<result>/menu/Menu.jsp</result>
</action>
</package>
<include file="manning/chapterTwo/chapterTwo.xml"/>
<include file="manning/chapterThree/chapterThree.xml"/>
<include file="manning/chapterThree/objectBacked/chapterThree.xml"/>
<include file="manning/chapterThree/modelDriven/chapterThree.xml"/>
<include file="manning/chapterFour/chapterFour.xml"/>
<include file="manning/chapterFive/chapterFive.xml"/>
<include file="manning/chapterSix/chapterSix.xml"/>
<include file="manning/chapterSeven/chapterSeven.xml"/>
<include file="manning/chapterEight/chapterEight.xml"/>
<include file="manning/chapterNine/chapterNine.xml"/>
<include file="manning/chapterTen/chapterTen.xml"/>
<include file="manning/chapterEleven/chapterEleven.xml"/>
</struts>
为什么我收到错误。我在 web.xml 中删除了一些关于 spring 的配置