求教：初学struts碰到了这个问题

[步景]

最近在学习struts，遇到了下面这个异常，当我把struts-config.xml中的datasource屏蔽掉后，这个错误就没了，当然也连不上数据库，求解……

控制台信息：
2012/11/30 下午 03:33:28 org.apache.catalina.core.AprLifecycleListener init
資訊: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: C:\Program Files\Java\jdk1.6.0_12\bin;.;C:\WINDOWS\Sun\Java\bin;C:\WINDOWS\system32;C:\WINDOWS;C:/Program Files/Java/jdk1.6.0_12/bin/../jre/bin/client;C:/Program Files/Java/jdk1.6.0_12/bin/../jre/bin;C:\Program Files\Java\jdk1.6.0_12\bin;C:\Program Files\Java\jdk1.6.0_12\jre\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\Program Files\TortoiseSVN\bin;C:\Program Files\MySQL\MySQL Server 5.1\bin;D:\Python32;E:\install_package\android\android-sdk-windows\android-sdk-windows\tools
2012/11/30 下午 03:33:28 org.apache.coyote.http11.Http11Protocol init
資訊: Initializing Coyote HTTP/1.1 on http-8080
2012/11/30 下午 03:33:28 org.apache.catalina.startup.Catalina load
資訊: Initialization processed in 329 ms
2012/11/30 下午 03:33:28 org.apache.catalina.core.StandardService start
資訊: Starting service Catalina
2012/11/30 下午 03:33:28 org.apache.catalina.core.StandardEngine start
資訊: Starting Servlet Engine: Apache Tomcat/6.0.29
2012/11/30 下午 03:33:28 org.apache.catalina.startup.HostConfig deployDescriptor
資訊: Deploying configuration descriptor demo.xml
2012/11/30 下午 03:33:29 org.apache.catalina.loader.WebappClassLoader validateJarFile
資訊: validateJarFile(D:\eclipse\workspace\demo\WebContent\WEB-INF\lib\servlet-api.jar) - jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class
2012/11/30 下午 03:33:29 org.apache.catalina.core.ApplicationContext log
資訊: Marking servlet action as unavailable
2012-11-30 15:33:29,615 ERROR [org.apache.struts.action.ActionServlet] - <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:2389)
at java.lang.Class.getConstructor0(Class.java:2699)
at java.lang.Class.newInstance0(Class.java:326)
at java.lang.Class.newInstance(Class.java:308)
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:212)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1173)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:993)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4350)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4659)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:546)
at org.apache.catalina.startup.HostConfig.deployDescriptor(HostConfig.java:637)
at org.apache.catalina.startup.HostConfig.deployDescriptors(HostConfig.java:563)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:498)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1277)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:321)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:785)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:445)
at org.apache.catalina.core.StandardService.start(StandardService.java:519)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:581)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.pool.impl.GenericObjectPool
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
... 35 more

struts-config.xml
<data-sources>
<data-source type="org.apache.commons.dbcp.BasicDataSource">
<set-property property="driverClassName"
value="com.mysql.jdbc.Driver" />
<set-property property="url"
value="jdbc:mysql://localhost:3306/demo" />
<set-property property="username" value="root" />
<set-property property="password" value="123456" />
<set-property property="maxActive" value="10" />
<set-property property="maxWait" value="5000" />
<set-property property="defaultAutoCommit" value="false" />
<set-property property="defaultReadOnly" value="false" />
<set-property property="validationQuery"
value="SELECT COUNT(*) FROM user" />
</data-source>
</data-sources>

lib