JSP + Struts: Error 9 java.lang.NoSuchFieldError: org.apache.log4j.Priority.INFO)

I need to create jsp page using struts

First i follow the below link
http://www.oracle.com/technology/obe/obe9051jdev/strutsvalidator/validator.htm#o

But when i run i got the following error.

500 Internal Server Error

java.lang.NoSuchFieldError:  org.apache.log4j.Priority.INFO  <=== i got no idea where to cause this problem

      at org.apache.commons.logging.impl.Log4JLogger.info(Log4JLogger.java:152)
      at org.apache.struts.util.PropertyMessageResources.<init>(PropertyMessageResources.java:127)
      at org.apache.struts.util.PropertyMessageResourcesFactory.createResources(PropertyMessageResourcesFactory.java:90)
      at org.apache.struts.util.MessageResources.getMessageResources(MessageResources.java:577)
      at org.apache.struts.action.ActionServlet.initInternal(ActionServlet.java:1329)
      at org.apache.struts.action.ActionServlet.init(ActionServlet.java:464)

Please help urgent