Struts2框架中的Action接口和ActionSupport类

1）Action接口的定义：
                  public interface Action{
                     //下述常量用于规范Result的名称
                     final static String SUCCESS="success";
                     final static String ERROR="error";
                     final static String INPUT="input";
                     final static String LOGIN="login";
                     final static String NONE="none";
                     //处理请求的默认方法
                     public String execute() throws Exception;
                  }          
                 2)ActionSupport类实现了Action接口，提供了
                  错误处理、表单验证、国际化等方法。
                   ActionSupport类的execute方法定义如下：
                     public String execute() throws Exception{
                          return SUCCESS;
                      }