core 2.0使用JWT认证园子里已经有挺多帖子了，但开发中发现认证未授权情况下返回的401状态码是没有任何信息的，业务中可能有需要返回一串错误的Json信息。在这里我分享一个自定义错误页面内容信息的方法，使用该扩展方法还可以捕获异常，将异常信息也转为json。
1.新建一个Api接口统一返回类ApiResult.cs（可替换成自己的）。
using System;using System.Collections.Generic;using System.Linq;using System.Threading.Tasks;namespace Jom.WebApi.Config{public class ApiResult{public bool Success { get; set; } = true;public string Msg { get; set; } = "";public string Type { get; set; } = "";public object Data { get; set; } = "";public object DataExt { get; set; } = "";}}
2.建立中间件ErrorHandlingMiddleware.cs
using Microsoft.AspNetCore.Builder;using Microsoft.AspNetCore.Http;using Newtonsoft.Json;using System;using System.Collections.Generic;using System.Linq;using System.Threading.Tasks;namespace Jom.WebApi.Config{public class ErrorHandlingMiddleware{private readonly RequestDelegate next;public ErrorHandlingMiddleware(RequestDelegate next){this.next = next;}public async Task Invoke(HttpContext context){try{await next(context);}catch (Exception ex){var statusCode = context.Response.StatusCode;if (ex is ArgumentException){statusCode = 200;}await HandleExceptionAsync(context, statusCode, ex.Message);}finally{var statusCode = context.Response.StatusCode;var msg = "";if (statusCode == 401){msg = "未授权";}else if (statusCode == 404){msg = "未找到服务";}else if (statusCode == 502){msg = "请求错误";}else if (statusCode != 200){msg = "未知错误";}if (!string.IsNullOrWhiteSpace(msg)){await HandleExceptionAsync(context, statusCode, msg);}}}//异常错误信息捕获，将错误信息用Json方式返回private static Task HandleExceptionAsync(HttpContext context, int statusCode, string msg){var result = JsonConvert.SerializeObject(new ApiResult() { Success=false,Msg=msg,Type= statusCode.ToString() });context.Response.ContentType = "application/json;charset=utf-8";return context.Response.WriteAsync(result);}}//扩展方法public static class ErrorHandlingExtensions{public static IApplicationBuilder UseErrorHandling(this IApplicationBuilder builder){return builder.UseMiddleware<ErrorHandlingMiddleware>();}}}
3.最后只要在Startup.cs中的Configure方法中加上一句，在Startup.cs中添加引用usingJom.WebApi.Config;使用扩展方法ErrorHandlingExtensions()使用错误码处理中间件。
//请求错误提示配置app.UseErrorHandling();
完整的Configure方法
public void Configure(IApplicationBuilder app, IHostingEnvironment env){if (env.IsDevelopment()){app.UseDeveloperExceptionPage();}//请求错误提示配置 app.UseErrorHandling();//使用认证授权 app.UseAuthentication();//使用mvcapp.UseMvc(routes =>{routes.MapRoute(name: "default",template: "api/{controller}/{action}/{id?}",defaults: new { controller = "Values", action = "Get" });});}
最后就完成了自定义401页面内容，同时还可以定义其他状态码如403，404，502，503等等，同时api接口报异常也将转化为特定的JSON格式。
postman中请求返回
