Net Filter之ActionFilterAttribute

过滤器类型

net core 有五种过滤器，每个过滤器类型在过滤器管道中的不同阶段执行：

1：IAuthorizationFilterAttribute 授权过滤器
2：IResourceFilterAttribute 资源过滤器
3：ExceptionFilterAttribute 异常过滤器
4：ActionFilterAttribute方法过滤器
5：ResultFilterAttribute 结果过滤器

Filter 执行顺序

ActionFilterAttribute

异步环绕操作的执行和操作结果的抽象筛选器。官方文档
方法过滤器：它会在执行Action方法前后被调用。这个可以在方法中用来处理传递参数和处理方法返回结果。

属性

方法

在过滤器中使用依赖注入

有时候我们可能需要读取程序运行环境的信息，根据不同的环境做出不同的响应内容

public void OnResultExecouting(ResultExecutingContext context)
{
    var env=(IHostingEnvironname)context.HttpContext.RequestService.GetService(typeof(IHostingEnvironment))
}

示例

先定义一个WeatherForecastActionFilterAttribute的Action Filter,

using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using System.Text.Json;
namespace Net6.Filter.Demo.Filters;
/// <summary>
/// WeatherForecast的 Action Filter
/// </summary>
public class CustomerActionFilterAttribute:ActionFilterAttribute
{
    /// <summary>
    /// Action方法调用之前执行
    /// </summary>
    /// <param name="context"></param>
    public override void OnActionExecuting(ActionExecutingContext context)
    {
        var descriptor = context.ActionDescriptor as ControllerActionDescriptor;
        string param = string.Empty;
        string globalParam = string.Empty;
        foreach (var arg in context.ActionArguments)
        {
            string value = JsonSerializer.Serialize(arg.Value);
            param += $"{arg.Key} : {value} \r\n";
            globalParam += value;
        }
        Console.WriteLine("OnActionExecuting,Action 方法调用之前执行");
        //Console.WriteLine($"webapi方法名称:【{descriptor.ActionName}】接收到参数为：{param}");
    }
    /// <summary>
    /// Action 方法调用后，Result 方法调用前执行
    /// </summary>
    /// <param name="context"></param>
    public override void OnActionExecuted(ActionExecutedContext context) {
        Console.WriteLine("OnActionExecuted,Action 方法调用后，Result 方法调用前执行");
    }
    /// <summary>
    /// Result 方法调用前执行
    /// </summary>
    /// <param name="context"></param>
    public override void OnResultExecuting(ResultExecutingContext context) {
        Console.WriteLine("OnResultExecuting,Result 方法调用前执行");
    }
    /// <summary>
    /// Result 方法调用后执行
    /// </summary>
    /// <param name="context"></param>
    public override void OnResultExecuted(ResultExecutedContext context)
    {
        var descriptor = context.ActionDescriptor as ControllerActionDescriptor;
        string result = string.Empty;
        if (context.Result is ObjectResult)
        {
            result = JsonSerializer.Serialize(((ObjectResult)context.Result).Value);
        }
        Console.WriteLine("OnResultExecuted,Result 方法调用后执行");
        //Console.WriteLine($"webapi方法名称【{descriptor.ActionName}】执行的返回值 :  {result}");
    }
}

再到需要使用WeatherForecastActionFilterAttribute的方法头部添加上属性标记

using Microsoft.AspNetCore.Mvc;
using Net6.Filter.Demo.Filters;
using Net6.Filter.Demo.Models;
namespace Net6.Filter.Demo.Controllers.FilterDemo;
public class FilterDemoController : AreaController
{
    private static readonly string[] Summaries = new[]
    {
    "Freezing", "Bracing", "Chilly", "Cool", "Mild", "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
};
    private readonly ILogger<FilterDemoController> _logger;
    public FilterDemoController(ILogger<FilterDemoController> logger)
    {
        _logger = logger;
    }
    [HttpGet(Name = "GetWeatherForecast")]
    [CustomerActionFilterAttribute]
    public IEnumerable<WeatherForecast> Get()
    {
        return Enumerable.Range(1, 5).Select(index => new WeatherForecast
        {
            Date = DateTime.Now.AddDays(index),
            TemperatureC = Random.Shared.Next(-20, 55),
            Summary = Summaries[Random.Shared.Next(Summaries.Length)]
        })
        .ToArray();
    }
}

ActionExecutedContext

操作筛选器的上下文，特别是 OnActionExecuted(ActionExecutedContext)) 调用。

属性

方法

ActionExecutingContext

操作筛选器的上下文

属性

方法

ResultExecutedContext

Properties

Methods

ResultExecutingContext

Properties

Methods