.net core MVC Filters 过滤器介绍

一、过滤器的优级依次介绍如下(逐次递减)：

　　Authorization Filter ->  Resource Filter -> Acton Filter -> Exception Filter -> Result Filter

　　的.net Core MVC 中同步过滤器，新增了异步过滤器，对数据可以进行异步处理。

　　1、Authorization Filter  （权限过滤器）

    /// <summary>
    /// 权限过滤器
    /// </summary>
    public class GlobalAuthorizationFilter : Attribute, IAuthorizationFilter
    {
        /// <summary>
        /// 优化权最高的过滤器
        /// </summary>
        /// <param name="context"></param>
        public void OnAuthorization(AuthorizationFilterContext context)
        {
            //context.Result = new ObjectResult("IAuthorizationFilter 过滤输出");
            Console.WriteLine("IAuthorizationFilter 过滤输出");
        }
    }

/// <summary>
    /// 异步权限过滤器
    /// </summary>
    public class GlobalAsyncAuthorizationFilter : Attribute, IAsyncAuthorizationFilter
    {
        /// <summary>
        /// 执行异步Action 过滤器
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public async Task OnAuthorizationAsync(AuthorizationFilterContext context)
        {
            Console.WriteLine("IAsyncAuthorizationFilter 拦截输出");
            await Task.CompletedTask;
        }
    }

　　2、Resource Filter （资源过滤器）

/// <summary>
    /// 资源过滤器
    /// </summary>
    public class GlobalResourceFilter : IResourceFilter
    {
        /// <summary>
        /// 获取资源后拦截
        /// </summary>
        /// <param name="context"></param>
        public void OnResourceExecuted(ResourceExecutedContext context)
        {
            Console.WriteLine("IResourceFilter OnResourceExecuted 输出");
        }

        /// <summary>
        /// 获取资源前拦截
        /// </summary>
        /// <param name="context"></param>
        public void OnResourceExecuting(ResourceExecutingContext context)
        {
            Console.WriteLine("IResourceFilter OnResourceExecuting 输出");
        }
    }

/// <summary>
    /// 异步资源加载过滤器
    /// </summary>
    public class GlobalAsyncResourceFilter : IAsyncResourceFilter
    {
        /// <summary>
        /// 
        /// </summary>
        /// <param name="context"></param>
        /// <param name="next"></param>
        /// <returns></returns>
        public async Task OnResourceExecutionAsync(ResourceExecutingContext context, ResourceExecutionDelegate next)
        {
            // 执行前
            await next.Invoke();

            // 执行后
            await OnExecutedAsync(context);
        }

        /// <summary>
        /// 执行后
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public async Task OnExecutedAsync(ResourceExecutingContext context)
        {
            Console.WriteLine("IAsyncResourceFilter 执行后");
            await Task.CompletedTask;
        }
    }

　　3、Acton Filter  (Action 过滤器)

/// <summary>
    /// Acion过滤器
    /// </summary>
    public class GlobalActonFilter : Attribute, IActionFilter
    {
        /// <summary>
        /// Acion 执行后拦截
        /// </summary>
        /// <param name="context"></param>
        public void OnActionExecuted(ActionExecutedContext context)
        {
            Console.WriteLine("IActionFilter OnActionExecuted Acion 执行后拦截");
        }

        /// <summary>
        /// Acion 执行前拦截
        /// </summary>
        /// <param name="context"></param>
        public void OnActionExecuting(ActionExecutingContext context)
        {
            Console.WriteLine("IActionFilter OnActionExecuting Acion 执行前拦截");
        }
    }

/// <summary>
    /// 异步 Action 过滤器
    /// </summary>
    public class GlobalAsyncActonFilter : Attribute, IAsyncActionFilter
    {
        /// <summary>
        /// 执行异步Action 过滤器
        /// </summary>
        /// <param name="context"></param>
        /// <param name="next"></param>
        /// <returns></returns>
        public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
        {
            // 执行前
            await next.Invoke();

            // 执行后
            await OnExecutedAsync(context);
        }

        /// <summary>
        /// 执行后
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public async Task OnExecutedAsync(ActionExecutingContext context)
        {
            Console.WriteLine("IAsyncActionFilter 执行后");
            await Task.CompletedTask;
        }
    }

　　4、Exception Filter (异常过滤器)

    /// <summary>
    /// 异常全局过滤器
    /// </summary>
    public class GlobalExceptionFilter : IExceptionFilter
    {
        /// <summary>
        /// 异常处理
        /// </summary>
        /// <param name="context">异常上下文</param>
        public void OnException(ExceptionContext context)
        {
            Console.WriteLine(context.Exception);
            //如果这里设为false，就表示告诉MVC框架，我没有处理这个错误。然后让它跳转到自己定义的错误页（设为true的话，就表示告诉MVC框架，异常我已经处理了。不需要在跳转到错误页了，也部会抛出黄页了）
            context.ExceptionHandled = false;
        }
    }

 /// <summary>
    /// 异步异常全局过滤器
    /// </summary>
    public class GlobalAsyncExceptionFilter : IAsyncExceptionFilter
    {
        /// <summary>
        /// 异常异步处理
        /// </summary>
        /// <param name="context">异常上下文</param>
        /// <returns></returns>
        public async Task OnExceptionAsync(ExceptionContext context)
        {
            Console.WriteLine(context.Exception.Message);
            //如果这里设为false，就表示告诉MVC框架，我没有处理这个错误。然后让它跳转到自己定义的错误页（设为true的话，就表示告诉MVC框架，异常我已经处理了。不需要在跳转到错误页了，也部会抛出黄页了）
            context.ExceptionHandled = false;
            await Task.CompletedTask;
        }

　　5、Result Filter (结果过滤器)

    /// <summary>
    /// 结果过滤器
    /// </summary>
    public class GlobalResultFilter : IResultFilter
    {
        /// <summary>
        /// 动作结果执行后
        /// </summary>
        /// <param name="context"></param>
        public void OnResultExecuted(ResultExecutedContext context)
        {
            Console.WriteLine("IResultFilter OnResultExecuted Acion 动作结果执行后");
        }

        /// <summary>
        /// 动作结果执行前
        /// </summary>
        /// <param name="context"></param>
        public void OnResultExecuting(ResultExecutingContext context)
        {
            Console.WriteLine("IResultFilter OnResultExecuting Acion 动作结果执行前");
        }
    }

    /// <summary>
    /// 异步 结果过滤器
    /// </summary>
    public class GlobalAsyncResultFilter : IAsyncResultFilter
    {

        /// <summary>
        /// 动作结果执行后
        /// </summary>
        /// <param name="context"></param>
        /// <param name="next"></param>
        /// <returns></returns>
        public async Task OnResultExecutionAsync(ResultExecutingContext context, ResultExecutionDelegate next)
        {
            await next.Invoke();
            await OnExecutedAsync(context);
        }

        /// <summary>
        /// 执行后
        /// </summary>
        /// <param name="context"></param>
        /// <returns></returns>
        public async Task OnExecutedAsync(ResultExecutingContext context)
        {
            Console.WriteLine("IAsyncResultFilter 执行");
            await Task.CompletedTask;
        }
    }

Demo 源码：https://github.com/intotf/netCore/tree/master/WebFilters