hibernate配置文件

<hibernate-mapping default-access="field" >
  <subclass name="org.jbpm.graph.action.MailAction"
            discriminator-value="M"
            extends="org.jbpm.graph.def.Action">
  </subclass>
</hibernate-mapping>请问包含这两个类的jar包都引人了，但是启动报错Caused by: org.hibernate.MappingException: Following super classes referenced in extends not found: org.jbpm.graph.def.Action，哪位能指点下   谢谢