webwork2.0.7中继承ActionSupport报的错

webwork2.0.7中继承ActionSupport报的如下 错：

java.lang.Error: Unresolved compilation problems:
The hierarchy of the type HelloWord is inconsistent
The type com.uwyn.rife.continuations.ContinuableObject cannot be resolved. It is indirectly referenced from required .class files
at ww.HelloWord.(HelloWord.java:5)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at com.opensymphony.xwork.ObjectFactory.buildBean(ObjectFactory.java:111)
at com.opensymphony.xwork.ObjectFactory.buildBean(ObjectFactory.java:123)
at com.opensymphony.xwork.ObjectFactory.buildAction(ObjectFactory.java:101)
at com.opensymphony.xwork.DefaultActionInvocation.createAction(DefaultAction
原因是在工程中没有引入rife-continuations.jar包