.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.geek-share.com/detail/2688291262.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);
}
}
}
}

 

转载于:https://www.cnblogs.com/taotaozhuanyong/p/11594732.html

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