ASP.NET MVC中利用AuthorizeAttribute实现访问身份是否合法以及Cookie过期问题的处理

话说来到上海已经快半年了，时光如白驹过隙，稍微不注意，时间就溜走了，倒是没有那么忙碌，闲暇之际来博客园还是比较多的，记得上次在逛博问的时候看到有同志在问MVC中Cookie过期后如何作相关处理，他在阐述那么多页面不可能都去一个个手动处理。其实MVC很牛逼的地方就是把Attribute利用的非常完美，接下来就来看下它是如何做到的吧！

第一步、我们要定义一个登录过滤标签-LoginFilterAttribute并且继承AuthorizeAttribute。来看下它内部是啥样子

 // Summary:
     //     Represents an attribute that is used to restrict access by callers to an
     //     action method.
     [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = true)]
     public class AuthorizeAttribute : FilterAttribute, IAuthorizationFilter
     {
         // Summary:
         //     Initializes a new instance of the System.Web.Mvc.AuthorizeAttribute class.
         public AuthorizeAttribute();

         // Summary:
         //     Gets or sets the user roles.
         //
         // Returns:
         //     The user roles.
         public string Roles { get; set; }
         //
         // Summary:
         //     Gets the unique identifier for this attribute.
         //
         // Returns:
         //     The unique identifier for this attribute.
         public override object TypeId { get; }
         //
         // Summary:
         //     Gets or sets the authorized users.
         //
         // Returns:
         //     The authorized users.
         public string Users { get; set; }

         // Summary:
         //     When overridden, provides an entry point for custom authorization checks.
         //
         // Parameters:
         //   httpContext:
         //     The HTTP context, which encapsulates all HTTP-specific information about
         //     an individual HTTP request.
         //
         // Returns:
         //     true if the user is authorized; otherwise, false.
         //
         // Exceptions:
         //   System.ArgumentNullException:
         //     The httpContext parameter is null.
         protected virtual bool AuthorizeCore(HttpContextBase httpContext);
         //
         // Summary:
         //     Processes HTTP requests that fail authorization.
         //
         // Parameters:
         //   filterContext:
         //     Encapsulates the information for using System.Web.Mvc.AuthorizeAttribute.
         //     The filterContext object contains the controller, HTTP context, request context,
         //     action result, and route data.
         protected virtual void HandleUnauthorizedRequest(AuthorizationContext filterContext);
         //
         // Summary:
         //     Called when a process requests authorization.
         //
         // Parameters:
         //   filterContext:
         //     The filter context, which encapsulates information for using System.Web.Mvc.AuthorizeAttribute.
         //
         // Exceptions:
         //   System.ArgumentNullException:
         //     The filterContext parameter is null.
         public virtual void OnAuthorization(AuthorizationContext filterContext);
         //
         // Summary:
         //     Called when the caching module requests authorization.
         //
         // Parameters:
         //   httpContext:
         //     The HTTP context, which encapsulates all HTTP-specific information about
         //     an individual HTTP request.
         //
         // Returns:
         //     A reference to the validation status.
         //
         // Exceptions:
         //   System.ArgumentNullException:
         //     The httpContext parameter is null.
         protected virtual HttpValidationStatus OnCacheAuthorization(HttpContextBase httpContext);
     }

这里我们要重写OnAuthorization这个方法。

接下来就看下LoginFilterAttibute这个"儿子"是怎么完成"老子"交待的任务了。直接上code

 public class LoginFilterAttribute:AuthorizeAttribute
     {

         private static string formsCookieName = FormsAuthentication.FormsCookieName;

         public override void OnAuthorization(AuthorizationContext filterContext)
         {
            HttpCookie formsCookie =
                 System.Web.CookieManager.GetCookie(formsCookieName);
             if (formsCookie == null)
             {
                 //页面Cookie过期后返回登录页面
                 RedirectToLoginPage(filterContext);
                 return;
             }

             bool autenticated = HttpContext.Current.User.Identity.IsAuthenticated;

             //一旦发现身份不合法就作相应的处理.
             if (!autenticated )
             {
                 //redirect to login
                 RedirectToLoginPage(filterContext);
                 return;
             }
             //if success add login data to context
         }
            private static void RedirectToLoginPage(AuthorizationContext filterContext)
         {
             if (filterContext.HttpContext.Request.IsAjaxRequest())
             {
                 filterContext.Result = new JsonResult()
                 {
                     Data = new {
                         status = "error",
                         message = "Unauthorized_Message"
                     },
                     JsonRequestBehavior= JsonRequestBehavior.AllowGet
                 };
                 return;
             }
 else
 {
          //返回登录页面的相关处理..........
 }
}

第二步、新建一个基类Controller-BaseController并且继承Controller。

     [LoginFilter]//此处就是我们上面定义的LoginFilterAttribute
     public abstract partial class BaseController : Controller
     {
         public BaseController(){ 

         }
       //........其他相关处理
     }

第三步、不是有很多页面吗？那我只要在对应的Controller去继承那个BaseController就实现了，在访问任何一个页面都会去作相应的过滤和处理。

 Public Class LoginController：BaseController
 {
      Public ActionResult Index（）
     {
       //........
        return  View();
     }
 }

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