struts extends 继承 （在抽象类中调用抽象方法，具体由其子类实现）

public abstract class SecurityAction extends BaseAction {

 public ActionForward execute(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
   throws Exception {
  /*User u=new User();
  u.setName("zw");
  request.getSession().setAttribute("user", u);//这个是为了执行下面的doExcetion()而加的
  */User user=(User)request.getSession().getAttribute("user");//获取session中的对象
  if(user==null||user.getName()==null){
   String url=request.getServletPath();
   String query=request.getQueryString();//request传的参数
   if(query!=null){
    request.setAttribute("signonAction", url+"?"+query);
   }
   else{
    request.setAttribute("signonAction", url);
   }
   System.out.println("url: "+url+"--query: "+query);
   return mapping.findForward("loginfail");
  }
  else{
   return doExecute(mapping,form,request,response);//由一个execute()跳转到另一个execute()
  }
 }

 protected abstract ActionForward doExecute(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
 throws Exception ;//由子类来实现方法，这个父类调用子类的方法
}

import org.apache.struts.action.Action;
import org.apache.struts.action.ActionServlet;

public class BaseAction extends Action {

 private String base="base";//通常这里是一个所有对象需要用到的 对象

 protected String getBase() {
  return base;
 }

 public void setServlet(ActionServlet servlet) {
  super.setServlet(servlet);
  this.base=servlet.toString();
  /*if (actionServlet != null) {
   ServletContext servletContext = actionServlet.getServletContext();
   WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext);
   this.petStore = (PetStoreFacade) wac.getBean("petStore");
  }*/ //从spring中获取对象
 }
}

public class SecurityActionImpl extends SecurityAction {

 protected ActionForward doExecute(ActionMapping mapping, ActionForm form,
   HttpServletRequest request, HttpServletResponse response)
   throws Exception {
  System.out.println("SecurityActionImpl: doExecute()");
  return mapping.findForward("success");
 }
}