MVC之自定义过滤器(ActionFilterAttribute)

一、自定义Filter

自定义Filter需要继承ActionFilterAttribute抽象类，重写其中需要的方法，来看下ActionFilterAttribute类的方法签名。

    //表示所有操作-筛选器特性的基类
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, Inherited = true, AllowMultiple = false)]
    public abstract class ActionFilterAttribute : FilterAttribute, IActionFilter, IResultFilter
    {
        protected ActionFilterAttribute();      
        //在Action执行之前由 MVC 框架调用。
        public virtual void OnActionExecuting(ActionExecutingContext filterContext);
        //在Action执行之后由 MVC 框架调用。
        public virtual void OnActionExecuted(ActionExecutedContext filterContext);
        //在执行Result之前由 MVC 框架调用。
        public virtual void OnResultExecuting(ResultExecutingContext filterContext);
        //在执行Result后由 MVC 框架调用。
        public virtual void OnResultExecuted(ResultExecutedContext filterContext);      
    }

过滤器代码

    //自定义过滤器
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public class LoginFilterAttribute : ActionFilterAttribute
    {
        ILogger log = LoggerFactory.GetChannelLog(typeof(LogInAuthorizeAttribute));

        /// <summary>
        /// 默认登录页面
        /// </summary>
        private static readonly string logUrl = ConfigFactory.WebEnvConfig.Items["LoginToGMS"];

        //通过配置cookie名称
        private static readonly  string cookieName = ConfigFactory.WebEnvConfig.Items["CookieName"];
        
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            try
            {
                log.Debug("自定义Cookie名称,CookieName:" + cookieName);

                var cookie = filterContext.HttpContext.Request.Cookies[cookieName];

                if (cookie == null)
                {
                     RedirectUrl(filterContext, logUrl);
                }
                log.Debug("cookieName:" + cookieName + "cookieValue:" + cookie.Value);
                FormsAuthenticationTicket ticket = FormsAuthentication.Decrypt(cookie.Value);
                if (ticket == null || string.IsNullOrEmpty(ticket.UserData)) {
                    log.Debug("解密失败! tick  is null or ticket UserData is null :");
                    RedirectUrl(filterContext, logUrl);
                }
                log.Debug("解密成功!tick:" + ticket.Name);
                LoginUser userData = JsonConvert.DeserializeObject<LoginUser>(ticket.UserData);
                HttpContext.Current.User = new System.Security.Principal.GenericPrincipal(new System.Web.Security.FormsIdentity(ticket),new string[0]);
                log.Debug("!HttpContext.Current.Request.IsAuthenticated:" + HttpContext.Current.Request.IsAuthenticated);
                log.Debug("获取成功!  Name：" + userData.User_Nm);
            }
            catch (Exception ex)
            {
                log.Error("解密cookie异常："+ex.Message);
                log.Error(ex);
                filterContext.HttpContext.Response.Cookies.Clear();
                RedirectUrl(filterContext, logUrl);
            }
            base.OnActionExecuting(filterContext);         
        }
        
        /// <summary>
        /// 跳转报错解决办法
        /// </summary>
        /// <param name="url"></param>
        public void RedirectUrl(ActionExecutingContext filterContext, string url)
        {
            filterContext.HttpContext.Response.Clear();//这里是关键，清除在返回前已经设置好的标头信息，这样后面的跳转才不会报错
            filterContext.HttpContext.Response.BufferOutput = true;//设置输出缓冲
            if (!filterContext.HttpContext.Response.IsRequestBeingRedirected)//在跳转之前做判断,防止重复
            {
                //filterContext.HttpContext.Response.Redirect(url, true);//在Filter中用Response.Redirect,虽然URL是跳转了，但是之后的Filter和Action还是会执行，不仅浪费资源，还会产生一些不必要的错误
                filterContext.Result = new RedirectResult(url);
            }
        }

注意过滤器也可以放在整个Controller类的顶部，表示该Controller下的所有Action都执行该项检查。这样一来，控制器里的代码非常漂亮，再也不用所有的Action里都充斥着判断登录的代码了。

顺便说下登录成功后如何将用户信息写入Cookie中

   LoginUser loginUser = new LoginUser();                  
   loginUser.UserId = userfile.User_Id;
   loginUser.User_Cd = userfile.User_Cd;
   loginUser.User_Nm = userfile.User_Nm;                   

   FormsAuthentication.SetAuthCookie(UserName, false);
   FormsAuthenticationTicket Ticket = new FormsAuthenticationTicket(1, UserName, DateTime.Now, DateTime.Now.AddTicks(FormsAuthentication.Timeout.Ticks), false, JsonConvert.SerializeObject(loginUser));
   string HashTicket = FormsAuthentication.Encrypt(Ticket);
   HttpCookie UserCookie = new HttpCookie(FormsAuthentication.FormsCookieName, HashTicket);
                      
   UserCookie.Domain = FormsAuthentication.CookieDomain;
   UserCookie.Path = "/"; 

同时在Web.config中配置如下：

<authentication mode="Forms">
    <forms path="/" loginUrl="/login" defaultUrl="/" protection="All" name=".newpower" domain="" timeout="60" slidingExpiration="true" />
</authentication>

二、带参数的自定义Filter

首先，还是按照之前添加自定义过滤器的方法，添加一个自定义过滤器，只是里面多了一个属性，代码如下：

public class FilterAttribute : ActionFilterAttribute
    {
        public string Message { get; set; }
 
        public override void OnActionExecuting(ActionExecutingContext filterContext)
        {
            base.OnActionExecuting(filterContext);
            filterContext.HttpContext.Response.Write("Action执行之前" + Message + "<br />");
        }
 
        public override void OnActionExecuted(ActionExecutedContext filterContext)
        {
            base.OnActionExecuted(filterContext);
            filterContext.HttpContext.Response.Write("Action执行之后" + Message + "<br />");
        }
 
        public override void OnResultExecuting(ResultExecutingContext filterContext)
        {
            base.OnResultExecuting(filterContext);
            filterContext.HttpContext.Response.Write("返回Result之前" + Message + "<br />");
        }
 
        public override void OnResultExecuted(ResultExecutedContext filterContext)
        {
            base.OnResultExecuted(filterContext);
            filterContext.HttpContext.Response.Write("返回Result之后" + Message + "<br />");
        }
    }

然后在调用过滤器的时候，添加上该参数，Controller代码如下：

[Filter(Message="刘备")]　　//参数给上
 public ActionResult Index()
{
      return View();
}

如果标签打到Controller上的话，FilterAttribute将作用到Controller下的所有的Action。

默认情况下Action上打了某个自定义标签后，虽然在Controller上也打上了此标签，但它只有Action上的标签起作用了。
补充：如果Action没有打上该标签，那么Controller上的标签便会被执行。

如果想让Action上的标签执行一次，然后Controller上的标签也执行一次，那么应该如何操作呢？

我们只需在FilterAttribute类的定义上打上标记[AttributeUsage(AttributeTargets.All, AllowMultiple = true)]即可【下面类的最上面红色字体部分】，也就是让其成为可以多次执行的Action。代码如下：

[AttributeUsage(AttributeTargets.All,AllowMultiple = true)]
public class FilterAttribute : ActionFilterAttribute
{
        public string Message { get; set; }
        ......

三、全局过滤器　

创建一个全局action过滤器  (在appstart  的 filterconfig中注册   filters.Add(new LoginFilterAttribute());)

这样就每个Action都会执行此过滤器，而不必每个Controller顶部都加上标签。    

public class FilterConfig
{
        public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        {
            filters.Add(new HandleErrorAttribute());
            //注册全局过滤器
            filters.Add(new LoginFilterAttribute() { Message = "全局" });
        }
}