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  • .Net Core MVC中过滤器简介

    在.Net Framework MVC 中有四种过滤器,授权过滤器(Authorize)、Action 过滤器、结果过滤器(Result)、异常过滤器(Exception)四种过滤器。在.Net Core MVC中,有五种过滤器,授权过滤器、Action过滤器、异常过滤器、结果过滤器、资源过滤器,新增了资源过滤器。

    .Net Core MVC和.Net Framework MVC在基本使用上差别不大,主要的还是框架的差别。其中路由是个很重要的东西,参考文章:https://www.cnblogs.com/durow/p/5992926.html

    Action过滤器、结果过滤器、Exception,三个特性,没有什么变化。在ExceptionFilter多了个Order参数,就是用来排序的。

    结果过滤器,包装了单个Action Result的执行,当且晋档Action方法成功执行完毕后才运行。它们是理想的围绕视图执行或格式处理的逻辑(所在之处)。继承Attribute,IResultFilter

     /// <summary>
     /// Result的Filter
     /// </summary>
     public class CustomResultFilterAttribute : Attribute, IResultFilter
     {
         //private Logger logger = Logger.CreateLogger(typeof(CustomResultFilterAttribute));
         public void OnResultExecuted(ResultExecutedContext context)
         {
             Console.WriteLine("OnResultExecuted Executed!");
             //logger.Info("OnResultExecuted Executed!");
         }
    
         public void OnResultExecuting(ResultExecutingContext context)
         {
             Console.WriteLine("OnResultExecuting Executing!");
             //logger.Info("OnResultExecuting Executing!");
         }
     }

    异常过滤器,为MVC隐藏程序为处理异常应用全局策略。继承ExceptionFilterAttribute

     /// <summary>
     /// 异常处理的Filter
     /// </summary>
     public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
     {
         private readonly IHostingEnvironment _hostingEnvironment;
         private readonly IModelMetadataProvider _modelMetadataProvider;
         //private Logger logger = Logger.CreateLogger(typeof(CustomExceptionFilterAttribute));
    
         /// <summary>
         /// IOC来的
         /// </summary>
         /// <param name="hostingEnvironment"></param>
         /// <param name="modelMetadataProvider"></param>
         public CustomExceptionFilterAttribute(
             IHostingEnvironment hostingEnvironment,
             IModelMetadataProvider modelMetadataProvider)
         {
             _hostingEnvironment = hostingEnvironment;
             _modelMetadataProvider = modelMetadataProvider;
         }
    
         /// <summary>
         /// 没有处理的异常,就会进来
         /// </summary>
         /// <param name="filterContext"></param>
         public override void OnException(ExceptionContext filterContext)
         {
             if (!filterContext.ExceptionHandled)//异常有没有被处理过
             {
                 string controllerName = (string)filterContext.RouteData.Values["controller"];
                 string actionName = (string)filterContext.RouteData.Values["action"];
                 string msgTemplate = "在执行 controller[{0}] 的 action[{1}] 时产生异常";
                 //logger.Error(string.Format(msgTemplate, controllerName, actionName), filterContext.Exception);
                 if (this.IsAjaxRequest(filterContext.HttpContext.Request))//检查请求头
                 {
                     filterContext.Result = new JsonResult(
                          new
                          {
                              Result = false,
                              PromptMsg = "系统出现异常,请联系管理员",
                              DebugMessage = filterContext.Exception.Message
                          }//这个就是返回的结果
                     );
                 }
                 else
                 {
                     var result = new ViewResult { ViewName = "~/Views/Shared/Error.cshtml" };
                     result.ViewData = new ViewDataDictionary(_modelMetadataProvider, filterContext.ModelState);
                     result.ViewData.Add("Exception", filterContext.Exception);
                     filterContext.Result = result;
                 }
                 filterContext.ExceptionHandled = true;
             }
         }
    
    
         private bool IsAjaxRequest(HttpRequest request)
         {
             string header = request.Headers["X-Requested-With"];
             return "XMLHttpRequest".Equals(header);
         }
     }
    View Code

    定义完ExceptionFilter,该怎么注册到全局呢?在Stratup.cs中ConfigureServer中,进行注册

    services.AddMvc(o =>
    {
        o.Filters.Add(typeof(CustomExceptionFilterAttribute));// 这里就是全局注册Filter
    
    }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

    Action 过滤器,包装了对单个Action方法的调用,可以将参数传递给Action并从中获得Action Result。继承IActionFilter

     /// <summary>
     /// Action的Filter`
     /// </summary>
     public class CustomActionFilterAttribute : Attribute, IActionFilter
     {
         private ILogger<CustomActionFilterAttribute> _logger = null;
         public CustomActionFilterAttribute(ILogger<CustomActionFilterAttribute> logger)
         {
             this._logger = logger;
         } 
         public void OnActionExecuted(ActionExecutedContext context)
         {
             //context.HttpContext.Response.WriteAsync("ActionFilter Executed!");
             Console.WriteLine("ActionFilter Executed!");
             //this._logger.LogDebug("ActionFilter Executed!");
         } 
         public void OnActionExecuting(ActionExecutingContext context)
         {
             //context.HttpContext.Response.WriteAsync("ActionFilter Executing!");
             Console.WriteLine("ActionFilter Executing!");
             //this._logger.LogDebug("ActionFilter Executing!");
         }
     }

    在Startup.cs中ConfigureServices进行注册

     //允许使用ServiceFilter 标记特性
     services.AddScoped<CustomActionFilterAttribute>();

    标记到Controller的ActionFilter

    /// <summary>
    /// 标记到Controller
    /// </summary>
    public class CustomControllerActionFilterAttribute : Attribute, IActionFilter
    {
        private ILogger<CustomControllerActionFilterAttribute> _logger = null;
        public CustomControllerActionFilterAttribute(ILogger<CustomControllerActionFilterAttribute> logger)
        {
            this._logger = logger;
        }
        public void OnActionExecuted(ActionExecutedContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executed!");
            Console.WriteLine("ActionFilter Executed!");
            //this._logger.LogDebug("ActionFilter Executed!");
        }
        public void OnActionExecuting(ActionExecutingContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executing!");
            Console.WriteLine("ActionFilter Executing!");
            //this._logger.LogDebug("ActionFilter Executing!");
        }
    }
     [TypeFilter(typeof(CustomControllerActionFilterAttribute),Order =-1)]
     public class ThirdController : Controller
     {
    }

    注册到全局的ActionFilter

    public class CustomGlobalActionFilterAttribute : Attribute, IActionFilter
    {
        private ILogger<CustomGlobalActionFilterAttribute> _logger = null;
        public CustomGlobalActionFilterAttribute(ILogger<CustomGlobalActionFilterAttribute> logger)
        {
            this._logger = logger;
        }
        public void OnActionExecuted(ActionExecutedContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executed!");
            Console.WriteLine("ActionFilter Executed!");
            //this._logger.LogDebug("ActionFilter Executed!");
        }
        public void OnActionExecuting(ActionExecutingContext context)
        {
            //context.HttpContext.Response.WriteAsync("ActionFilter Executing!");
            Console.WriteLine("ActionFilter Executing!");
            //this._logger.LogDebug("ActionFilter Executing!");
        }
    }

    还是要在Startup中进行全局的注册

    services.AddMvc(o =>
    {
        o.Filters.Add(typeof(CustomGlobalActionFilterAttribute));// 这里就是全局注册Filter
    
    }).SetCompatibilityVersion(CompatibilityVersion.Version_2_2);

    分别对全局、控制器、Action注册了ActionFilter默认执行顺序:

      全局OnActionExecuting===》控制器的OnActionExecuting====》Action的OnActionExecuting====》执行Action ====》Action的OnActionExecuted====》控制器的OnActionExecuted====》全局的OnActionExecuted。类似于一个俄罗斯套娃,也可以说是一个洋葱模型。

    资源过滤器,是授权之后第一个用来处理请求的过滤器,也是最后一个接触到请求的过滤器(因为之后就会离开过滤器管道)。在性能方面,资源过滤器在实现缓存或短路过滤器管道尤其有用。继承IResourceFilter

     /// <summary>
     /// 自定义的资源Filter
     /// </summary>
     public class CustomResourceFilterAttribute : Attribute, IResourceFilter
     {
         private static readonly Dictionary<string, object> _Cache = new Dictionary<string, object>();
         private string _cacheKey;
         /// <summary>
         /// 控制器实例化之前
         /// </summary>
         /// <param name="context"></param>
         public void OnResourceExecuting(ResourceExecutingContext context)
         {
             _cacheKey = context.HttpContext.Request.Path.ToString();
             if (_Cache.ContainsKey(_cacheKey))
             {
                 var cachedValue = _Cache[_cacheKey] as ViewResult;
                 if (cachedValue != null)
                 {
                     context.Result = cachedValue;
                 }
             }
         }
         /// <summary>
         /// 把请求都处理完的
         /// </summary>
         /// <param name="context"></param>
         public void OnResourceExecuted(ResourceExecutedContext context)
         {
             if (!String.IsNullOrEmpty(_cacheKey) &&
                 !_Cache.ContainsKey(_cacheKey))
             {
                 var result = context.Result as ViewResult;
                 if (result != null)
                 {
                     _Cache.Add(_cacheKey, result);
                 }
             }
         }
     }
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  • 原文地址:https://www.cnblogs.com/taotaozhuanyong/p/11594732.html
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