初学者的struts问题..提示can not resolve symbol:class MessageResourses

孙mm书上的第一个例子..在编译的时候出现一个错误
can not resolve symbol:class MessageResourses
但我已经import org.apache.struts.util.MessageResources;
第一次写struts,还请大家多多帮助

package hello;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionMessage;
import org.apache.struts.action.ActionMessages;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.util.MessageResources;

public final class HelloAction extends Action
{
public ActionForward execute(ActionMapping mapping,ActionForm form,HttpServletRequest request,HttpServletResponse response) throws Exception
{
MessageResourses messages = getResources(request);
ActionMessages errors = new ActionMessages();
String userName = (String)((HelloForm)form).getUserName();

String badUserName = "Monster";

if(userName.equalsIgnoreCase(badUserName))
{
errors.add("username",new ActionMessage("hello.dont.talk.to.monster",badUserName));
saveErrors(request,errors);
return(new ActionForward(mapping.getInput()));
}

PersonBean pb = new PersonBean();
pb.setUserName(userName);
pb.saveToPersistentStore();

request.setAttribute(Constants.PERSON_KEY,pb);
request.removeAttribute(mapping.getAttribute());

return (mapping.findForward("SayHello"));
}
};