求哪位大牛给看一下，小弟感激不尽

Stacktraces
org.apache.struts2.json.JSONException: org.apache.struts2.json.JSONException: java.lang.reflect.InvocationTargetException 
    org.apache.struts2.json.JSONWriter.bean(JSONWriter.java:243)
    org.apache.struts2.json.JSONWriter.process(JSONWriter.java:165)
    org.apache.struts2.json.JSONWriter.value(JSONWriter.java:131)
    org.apache.struts2.json.JSONWriter.write(JSONWriter.java:99)
    org.apache.struts2.json.JSONUtil.serialize(JSONUtil.java:112)
    org.apache.struts2.json.JSONResult.execute(JSONResult.java:198)
   .invoke(DefaultActionInvocation.java:237)
    com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:179)
    com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:237)
      org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:267)
       
    
java.lang.IllegalStateException: getInputStream() has already been called for this request 
    org.apache.catalina.connector.Request.getReader(Request.java:1125)
    org.apache.catalina.connector.RequestFacade.getReader(RequestFacade.java:470)
    javax.servlet.ServletRequestWrapper.getReader(ServletRequestWrapper.java:248)
       。。
其实action已经进入了，但是就是返回结果为json的时候，页面上报这个错误！