MVC擴充Filter,通過繼承ActionFilterAttribute為登入密碼加密

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與ActionFilter相關的介面有2個：

 

□ IActionFilter 對action執行前後處理

void OnActionExecuting(ActionExecutingContext filterContext);
可以在此對請求處理，甚至開啟一個新的請求。

 

void OnActionExecuted(ActonExecutedContext filterContext);
可以在此對返回結果處理，甚至取消返回結果。

 

關於參數ActionExecutingContext和ActonExecutedContext共有的：
都繼承於ControllerContext。
都有ActionDescriptor屬性：提供了action的細節
都有ActionResult屬性：當設定為null的時候取消整個請求

 

關於ActonExecutedContext專屬的：
Canceled屬性：bool類型，ActionExecutedContext是否被其它action filter取消
Exception屬性：action filter和action拋出的異常
ExceptionHandled屬性：bool類型，異常是否被處理

 

□ IResultFilter 對action返回結果前後做處理

方法與屬性與IActionFilter類似。
void OnResultExecuted(ResultExecutedContext filterContext);
void OnResultExecuting(ResultExecutingContext filterContext);

 

  執行個體：繼承ActionFilterAttribute為登入密碼加密

ActionFilterAttribute包含了如下4個方法：
void OnActionExecuting(ActionExecutingContext filterContext);
void OnActionExecuted(ActonExecutedContext filterContext);
void OnResultExecuted(ResultExecutedContext filterContext);
void OnResultExecuting(ResultExecutingContext filterContext);
所以，我們可以在衍生類別中重寫這4個方法。

 

□ 思路

→在執行action之前對密碼加密
→在執行action之後，根據是否登入成功，來決定返回成功或重新登入視圖
→在action返回結果之後，再追加一些內容

 

□ 繼承ActionFilterAttribute

using System;

using System.Security.Cryptography;

using System.Text;

using System.Web.Mvc;

using System.Web.Security;

namespace MvcApplication1.Extension

{

    public class EncryptLoginAttribute : ActionFilterAttribute

    {

        private string username;

        private string password;

        private bool isAuthorized = false;

        private string longdate;

        private string lastTry;

        public override void OnActionExecuting(ActionExecutingContext filterContext)

        {

            username = filterContext.HttpContext.Request.Form["username"];

            password = filterContext.HttpContext.Request.Form["password"];

            MD5 md5Hash = MD5.Create();

            string md5Password = GetMD5Hash(md5Hash, password);

            bool result = Membership.ValidateUser(username, md5Password);

            if (result)

            {

                FormsAuthentication.SetAuthCookie(username, false);

                isAuthorized = true;

                longdate = DateTime.Now.ToLongDateString();

            }

            else

            {

                isAuthorized = false;

                lastTry = DateTime.Now.ToShortDateString() + "-" + DateTime.Now.ToShortTimeString();

            }

        }

        public override void OnActionExecuted(ActionExecutedContext filterContext)

        {

            if (isAuthorized)

            {

                filterContext.Result = new ViewResult(){ViewName = "Welcome"};

            }

            else

            {

                ViewResult result = new ViewResult();

                result.ViewName = "Index";

                result.ViewBag.message = "Login fail";

                filterContext.Result = result;

            }

        }

        public override void OnResultExecuted(ResultExecutedContext filterContext)

        {

            if (filterContext.Exception == null && !filterContext.Canceled)

            {

                ViewResult result = (ViewResult)filterContext.Result;

                if (result != null)

                {

                    if (result.ViewName == "Welcome")

                    {

                        filterContext.HttpContext.Response.Write("<p style=‘color:Green;‘><br/>Today is "

+ longdate + "<br/></p>");

                    }

                    else if (result.ViewName == "Index")

                    {

                        filterContext.HttpContext.Response.Write("<p style=‘color:Red;‘><br />Last Login attemp at "+lastTry+"<br/></p>");

                    }

                    filterContext.Result = result;

                }

            }

        }

        private static string GetMD5Hash(MD5 md5Hash, string input)

        {

            //string→byte[]

            byte[] data = md5Hash.ComputeHash(Encoding.UTF8.GetBytes(input));

            StringBuilder stringBuilder = new StringBuilder();

            foreach (byte b in data)

            {

                stringBuilder.Append(b.ToString("x2"));

            }

            return stringBuilder.ToString();

        }

    }

}

 

□ HomeController

using System.Web.Mvc;

using System.Web.Security;

using MvcApplication1.Extension;

namespace MvcApplication1.Controllers

{

    public class HomeController : Controller

    {

        public ActionResult Index()

        {

            return View();

        }

        [HttpPost]

        [EncryptLogin]

        public ActionResult Login(string username, string password)

        {

            //TODO:儲存到資料庫

            return null;

        }

        public ActionResult SignOut()

        {

            FormsAuthentication.SignOut();

            return RedirectToAction("Index");

        }

    }

}

 

□ Home/Index.cshtml為登入頁

@{

    ViewBag.Title = "Index";

    Layout = "~/Views/Shared/_Layout.cshtml";

}

<h2>Index</h2>

<p style="color: red;">@ViewBag.message</p>

@using (Html.BeginForm("Login", "Home", FormMethod.Post, new {id = "loginForm"}))

{

    <p>

        使用者名稱：@Html.TextBox("username", null, new {style = "width:100px"})

    </p>

    <p>

        密碼： @Html.Password("password", null, new {style = "width: 100px"})

    </p>

    <p>

        <input type="submit" name="login" value="登入"/>

    </p>

}

 

□ web.config相關配置

    <authentication mode="Forms">
      <forms loginUrl="~/Home/Index" timeout="2880">
        <credentials passwordFormat="Clear">
          <user name="name" password="21218cca77804d2ba1922c33e0151105"/>
        </credentials>
      </forms>
    </authentication>

 

□ 登入成功視圖：/Shared/Welcome.cshtml

@{
    ViewBag.Title = "Welcome";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>登入成功~~</h2>
@Html.ActionLink("登出","SignOut","Home")

 

登入頁：

 

 

登入失敗：

 

□ 如果想在全域使用

filters.Add(new EncryptLoginAttribute());

 

□ 備忘

暫沒有把登入成功顯示頁面調試出來，因為，當使用FormsAuthentication.Authenticate(username, md5Password)時，提示此方法已經過時；而使用Membership.ValidateUser(username, md5Password)時，對應的Web.config如何配置，暫沒細究。

 

參考資料：
MVC Filters Part 3 - Action Filter and Action Result Filter