求助JDOM+XPath编程

Question

在JBuilder下类库中和工程扩展库中都加入了jaxen-core.jar和jaxen-jdom还是出现以下错误:
java.lang.NoClassDefFoundError: org/jaxen/BaseXPath
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:141)
at org.jdom.xpath.XPath.newInstance(XPath.java:126)
at org.jdom.xpath.XPath.selectSingleNode(XPath.java:368)
at XMLProcess.readXML.parsePolicy(readXML.java:35)
at XMLProcess.readXML.main(readXML.java:63)
Exception in thread "main" 
并且在去掉XPath相前的程序段后还是出现相同的错误,想不通,请求指点.