Jfreechart 中DisplayChart找不到

 我在JSP中用到DisplayChart这个Jfreechart的系统类，在web.xml里加入了如下配置：
 <servlet>
  <servlet-name>DisplayChart</servlet-name> 
  <servlet-class>org.jfree.chart.servlet.DisplayChart</servlet-class> 
  </servlet>
  <servlet-mapping>
  <servlet-name>DisplayChart</servlet-name> 
  <url-pattern>/servlet/DisplayChart</url-pattern> 
  </servlet-mapping>而且也把jfreechart的jar包放到WEB-INF/lib里面
在本地是工作正常的
可是当我发不到服务器上的时候，图却无法正常显示，报错如下：
00000040 ServletWrappe E   [Servlet Error]-[DisplayChart]: java.lang.ClassNotFoundException: DisplayChart
at com.ibm.ws.classloader.CompoundClassLoader.findClass(CompoundClassLoader.java:480)
at com.ibm.ws.classloader.CompoundClassLoader.loadClass(CompoundClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:597)
at java.beans.Beans.instantiate(Beans.java:202)
at java.beans.Beans.instantiate(Beans.java:63)
at com.ibm.ws.webcontainer.servlet.ServletWrapper$1.run(ServletWrapper.java:1335)
at com.ibm.ws.security.util.AccessController.doPrivileged(AccessController.java:118)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.loadServlet(ServletWrapper.java:1330)
at com.ibm.ws.wswebcontainer.servlet.ServletWrapper.loadServlet(ServletWrapper.java:388)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.initialize(ServletWrapper.java:1244)
at com.ibm.ws.wswebcontainer.servlet.ServletWrapper.initialize(ServletWrapper.java:152)
at com.ibm.wsspi.webcontainer.extension.WebExtensionProcessor.createServletWrapper(WebExtensionProcessor.java:99)
at com.ibm.ws.webcontainer.extension.WebExtensionProcessor.createServletWrapper(WebExtensionProcessor.java:40)
at com.ibm.ws.webcontainer.extension.InvokerExtensionProcessor.handleRequest(InvokerExtensionProcessor.java:402)
at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3444)
at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:267)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:815)
at com.ibm.ws.wswebcontainer.WebContainer.handleRequest(WebContainer.java:1466)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:119)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:458)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:387)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:102)
at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:136)
at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:195)
at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:743)
at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:873)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1473)为什么呢？我已经把jar包放好了呀
困扰啊