struts常用扩展

            用户验证,错误异常处理,这个看似小事,但有时候处理也比较麻烦,随时有可能处理不好!

            一,用户验证处理

• 通过自定义标签直接添加在需要用户验证的页面 
• 通过覆盖struts 的RequestProcessor的processRole(),从而获得用户验证功能.
• 通过编写一个Action验证基类,子类继承而获得用户验证功能.

        1)自定义标签实现验证

java 代码

public final  class CheckLogin extends TagSupport{

        public int doStartTag() throws JspException{

             return (SKIP_BODY);
    }

       public int doEndTag() extends JspException{

            HttpSession session=pageContext.getSession();
            String userName=sesssion.getAttribute("USERNAME");
            if(userName==null){
                   pageContext.forward("xxxxx.jsp") ; //错误页面
                   return (SKIP_PAGE);
            }
            return (EVAL_PAGE);
   }

        2)struts 的RequestProcessor的processRole(),从而获得用户验证功能

java 代码

protected boolean processRoles (ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                                    throws IOException, ServletException{

         HttpSession session=request.getSession();
         String userName=session.getAttribute("USERNAME");
         if(userName==null){
                RequestDispatcher rd=request.getDispathcher("XXXX.jsp");//返回错误页面
                rd.forward(request,response);
                return false;
        }
        return true;
}

       3)编写一个Action验证基类,子类继承而获得用户验证功能.

java 代码

public abstract class CheckBaseAction extends Action{

       public final ActionForward execute(ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                                    throws IOException, ServletException {

                HttpSession session=request.getSession();
                String userName=session.getAttribute("USERNAME");
                if(userName==null){
                         return (mapping.findForward("login"));
               }
                return doExecute(mapping,request,response);
    }

      public abstract  ActionForward doExecute(ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                                    throws IOException, ServletException ;

}

       第三种灵活性比前2种强点,但与struts耦合比较强,或者可以使用另一种filter来实现用户检验也不错的选择!

       二.异常处理

•   通过Servlet异常处理,只要简单地在Web.xml里配置异常处理类型和返回页面
•   通过Struts的异常处理机制,在struts-config.xml配置局部异常和全局异常
•   通过编写一个Action 异常基类,子类继承而获得异常处理功能

         1) Servlet异常处理

xml 代码

<error-page>
   <error-code>404error-code>
   <location>XXX.jsplocation> <!---->
error-page>

<error-page>
    <exception-type>java.lang.NullPointerExceptionexception-type>
    <location>XXX.jsplocation> <!---->
error-page>

        2)Struts的异常处理机制,在struts-config.xml配置局部异常和全局异常

xml 代码

<!---->
   <global-exceptions>
            <exception type="java.lang.exception"
                               key="action.errors.exception"
                               path="/error.jsp"/>
   global-exceptions>

<!---->
    <action-mappings>
            <action path="/Login"
                          type="cn.com.sqicoo.LoginAction"
                          name="LoginForm"
                          input="/login.jsp">
           <exception type="java.lang.exception"
                               key="action.errors.exception"  >
           <forward name="success" path="/login_success.jsp"/>
            action>
    action-mappings>

        3)编写一个Action 异常基类,子类继承而获得异常处理功能

java 代码

public abstract class ErrorBaseAction extends Action{

       public final ActionForward execute(ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                                    throws IOException, ServletException {
              try{
                     return doExecute(mapping,form,request,response);
              }catch(Exception ex){
                     return doException(ex,mapping,form,request,response);
              }
    }

      public  ActionForward doException(Exception ex,
                                    ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                                    throws IOException, ServletException {
                 // 异常处理
                  return mapping.findForward("XXX");//返回页面
      }

       public abstract  ActionForward doExecute(ActionMapping mapping,
                                    ActionForm form,
                                    HttpServletRequest request,
                                    HttpServletResponse response)
                                    throws IOException, ServletException;

}