请看我的struts-config.xml
<?xml version= "1.0 " encoding= "UTF-8 "?>
<!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.2//EN " "http://struts.apache.org/dtds/struts-config_1_2.dtd ">
<struts-config>
<data-sources>
<data-source type= "org.apache.commons.dbcp.BasicDataSource ">
<set-property property= "driverClassName " value= "org.gjt.mm.mysql.Driver "/>
<set-property property= "url " value= "jdbc:mysql://localhost:3306/addressbooksample "/>
<set-property property= "username " value= "root "/>
<set-property property= "password " value= "MyNewPassword "/>
</data-source>
</data-sources>
<form-beans />
<global-exceptions />
<global-forwards />
<action-mappings />
<message-resources parameter= "com.statestreet.addressbook.struts.ApplicationResources " />
</struts-config>
我已经将struts-legacy.jar，commons-dbcp-1.2.1.jar，commons-pool-1.2.jar，commons-collections-3.2.jar包放入tomcat的common/lib目录中，/WEB-INF/lib中也有这些包。可是我启动tomcat服务的时候依然有这些错误，请问如何解决？
严重: Unable to initialize Struts ActionServlet due to an unexpected exception or error thrown, so marking the servlet as unavailable. Most likely, this is due to an incorrect or missing library dependency.
java.lang.NoClassDefFoundError: org/apache/commons/pool/impl/GenericObjectPool
at java.lang.Class.getDeclaredConstructors0(Native Method)
at java.lang.Class.privateGetDeclaredConstructors(Class.java:2357)
at java.lang.Class.getConstructor0(Class.java:2671)
at java.lang.Class.newInstance0(Class.java:321)
at java.lang.Class.newInstance(Class.java:303)
at org.apache.struts.util.RequestUtils.applicationInstance(RequestUtils.java:143)
at org.apache.struts.action.ActionServlet.initModuleDataSources(ActionServlet.java:805)
at org.apache.struts.action.ActionServlet.init(ActionServlet.java:335)
at javax.servlet.GenericServlet.init(GenericServlet.java:211)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1105)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:932)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:3917)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4201)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:759)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:739)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:524)
at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:904)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:867)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:474)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1122)