Struts2访问Servlet的三种方式

package com.pc.web.action; import javax.servlet.ServletContext; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse;  import org.apache.struts2.interceptor.ServletRequestAware; import org.apache.struts2.interceptor.ServletResponseAware; import org.apache.struts2.util.ServletContextAware;  import com.opensymphony.xwork2.ActionSupport;   public class ActionTest7 extends ActionSupport implements ServletRequestAware,ServletResponseAware,ServletContextAware {    private HttpServletRequest request;   private HttpServletResponse response;   private ServletContext application;       public String demo(){     System.out.println(request);     System.out.println(response);     System.out.println(application);     System.out.println(request.getSession());     return SUCCESS;   }    @Override   public void setServletRequest(HttpServletRequest request) {     this.request = request;   }    @Override   public void setServletResponse(HttpServletResponse response) {     this.response = response;   }    @Override   public void setServletContext(ServletContext application) {     this.application = application;   } }