.NetCore Web Api 利用ActionFilterAttribute统一接口返回值格式

.Net Core 同 Asp.Net MVC一样有几种过滤器，这里不再赘述每个过滤器的执行顺序与作用。

在实际项目开发过程中，统一API返回值格式对前端或第三方调用将是非常必要的，在.NetCore中我们可以通过ActionFilterAttribute来进行统一返回值的封装。

在封装之前我们需要考虑下面几个问题：

1，需要对哪些结果进行封装

我目前的做法是，只对ObjectResult进行封装，其他的类型：FileResult,ContentResult,EmptyResult,RedirectResult不予处理

2，对异常错误的封装

既然是统一返回值，当然也要考虑接口异常的问题了

但是不是所有的异常我们都需要返回给前端的，我们可能需要自定义一个业务异常，业务异常可以在前端进行友好提示，系统异常完全没必要抛出给前端或第三方，且需要对系统异常进行日志记录

项目结构：

Exceptions：自定义业务异常

Filters：自定义过滤器（统一结果封装，全局异常）

Models：统一结果实体

部分代码：

using System;
 
namespace NetCoreCommonResult.Exceptions
{
    /// <summary>
    /// 自定义业务异常，可以由前端抛出友好的提示
    /// </summary>
    public class BizException:Exception
    {
        public BizException()
        {
 
        }
        public BizException(string message):base(message)
        {
 
        }
        public BizException(string message, Exception ex) : base(message, ex)
        {
 
        }
    }
}

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
 
namespace NetCoreCommonResult.Filters
{
    public class CommonResultFilterAttribute : ActionFilterAttribute
    {
        public override void OnResultExecuting(ResultExecutingContext context)
        {
            if (context.Result is ObjectResult objRst)
            {
                if (objRst.Value is Models.ApiResult)
                    return;
                context.Result = new ObjectResult(new Models.ApiResult
                {
                    Success = true,
                    Message = string.Empty,
                    Data = objRst.Value
                });
            }
        }
    }
}

using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.Extensions.Logging;
 
namespace NetCoreCommonResult.Filters
{
    public class GlobalExceptionFilterAttribute : ExceptionFilterAttribute
    {
        private readonly ILogger<GlobalExceptionFilterAttribute> _logger;
        public GlobalExceptionFilterAttribute(ILogger<GlobalExceptionFilterAttribute> logger)
        {
            _logger = logger;
        }
        public override void OnException(ExceptionContext context)
        {
            context.ExceptionHandled = true;
            var isBizExp = context.Exception is Exceptions.BizException;
            context.Result = new ObjectResult(new Models.ApiResult
            {
                Success = false,
                Message = context.Exception.Message
            });
            //非业务异常记录errorLog,返回500状态码，前端通过捕获500状态码进行友好提示
            if (isBizExp == false)
            {
                _logger.LogError(context.Exception, context.Exception.Message);
                context.HttpContext.Response.StatusCode = 500;
            }
            base.OnException(context);
        }
    }
}

Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
 
namespace NetCoreCommonResult
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }
 
        public IConfiguration Configuration { get; }
 
        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddLogging();
            services.AddControllers(ops =>
            {
                //添加过滤器
                ops.Filters.Add(new Filters.CommonResultFilterAttribute());
                //GlobalExceptionFilterAttribute构造中注入其他服务，需要通过ServiceFilter添加
                ops.Filters.Add(new Microsoft.AspNetCore.Mvc.ServiceFilterAttribute(typeof(Filters.GlobalExceptionFilterAttribute)));
            });
            //注册GlobalExceptionFilterAttribute
            services.AddScoped<Filters.GlobalExceptionFilterAttribute>();
        }
 
        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Error");
            }
 
            app.UseStaticFiles();
 
            app.UseRouting();
 
            app.UseAuthorization();
 
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}

最后新建一个Controller然后写上几个不同返回值的的Action

using Microsoft.AspNetCore.Mvc;
using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
 
namespace NetCoreCommonResult.Controllers
{
    [Route("api/[controller]")]
    [ApiController]
    public class HomeController : ControllerBase
    {
        /// <summary>
        /// string
        /// </summary>
        /// <returns></returns>
        [HttpGet]
        public string Index() => "Welecome to .NetCore";
 
        /// <summary>
        /// 跳转，不处理
        /// </summary>
        /// <returns></returns>
        [HttpGet("redirect")]
        public ActionResult Redirect() => RedirectToAction("Index");
 
        /// <summary>
        /// 
        /// </summary>
        /// <returns></returns>
        [HttpGet("num")]
        public int Num() => 10;
 
        /// <summary>
        /// 异步
        /// </summary>
        /// <returns></returns>
        [HttpGet("async")]
        public Task<IEnumerable<string>> TaskString() =>Task.FromResult<IEnumerable<string>>(new[] { "A","B","C"});
        /// <summary>
        /// 文件输出，不处理
        /// </summary>
        /// <returns></returns>
        [HttpGet("file")]
        public ActionResult GetFile() => File(Encoding.UTF8.GetBytes("File String"), "text/plain");
 
        /// <summary>
        /// 空返回值，不处理
        /// </summary>
        /// <returns></returns>
        [HttpGet("empty")]
        public ActionResult Empty() => Empty();
        /// <summary>
        /// contentResult 不处理
        /// </summary>
        /// <returns></returns>
        [HttpGet("content")]
        public ActionResult Content() => Content("this is content");
        /// <summary>
        /// 异常，返回500错误
        /// </summary>
        /// <returns></returns>
        [HttpGet("exception")]
        public ActionResult GetException() => throw new InvalidOperationException("invalid");
        /// <summary>
        /// 自定义异常，返回200
        /// </summary>
        /// <returns></returns>
        [HttpGet("bizException")]
        public ActionResult GetBizException() => throw new Exceptions.BizException("bizException");
 
    }
}