ASP.NET CORE学习教程之自定义异常处理详解

/// <summary>
 /// 异常中间件配置对象
 /// </summary>
 public class CustomExceptionMiddleWareOption
 {
 public CustomExceptionMiddleWareOption(
  CustomExceptionHandleType handleType = CustomExceptionHandleType.JsonHandle,
  IList<PathString> jsonHandleUrlKeys = null,
  string errorHandingPath = "")
 {
  HandleType = handleType;
  JsonHandleUrlKeys = jsonHandleUrlKeys;
  ErrorHandingPath = errorHandingPath;
 }

 /// <summary>
 /// 异常处理方式
 /// </summary>
 public CustomExceptionHandleType HandleType { get; set; }

 /// <summary>
 /// Json处理方式的Url关键字
 /// <para>仅HandleType=Both时生效</para>
 /// </summary>
 public IList<PathString> JsonHandleUrlKeys { get; set; }

 /// <summary>
 /// 错误跳转页面
 /// </summary>
 public PathString ErrorHandingPath { get; set; }
 }

 /// <summary>
 /// 错误处理方式
 /// </summary>
 public enum CustomExceptionHandleType
 {
 JsonHandle = 0, //Json形式处理
 PageHandle = 1, //跳转网页处理
 Both = 2  //根据Url关键字自动处理
 }

/// <summary>
 /// 管道请求委托
 /// </summary>
 private RequestDelegate _next;

 /// <summary>
 /// 配置对象
 /// </summary>
 private CustomExceptionMiddleWareOption _option;

 /// <summary>
 /// 需要处理的状态码字典
 /// </summary>
 private IDictionary<int, string> exceptionStatusCodeDic;

 public CustomExceptionMiddleWare(RequestDelegate next, CustomExceptionMiddleWareOption option)
 {
  _next = next;
  _option = option;
  exceptionStatusCodeDic = new Dictionary<int, string>
  {
  { 401, "未授权的请求" },
  { 404, "找不到该页面" },
  { 403, "访问被拒绝" },
  { 500, "服务器发生意外的错误" }
  //其余状态自行扩展
  };
 }

public async Task Invoke(HttpContext context)
 {
  Exception exception = null;
  try
  {
  await _next(context); //调用管道执行下一个中间件
  }
  catch (Exception ex)
  {
  context.Response.Clear(); 
  context.Response.StatusCode = 500; //发生未捕获的异常，手动设置状态码
  exception = ex;
  }
  finally
  {
  if (exceptionStatusCodeDic.ContainsKey(context.Response.StatusCode) && 
   !context.Items.ContainsKey("ExceptionHandled")) //预处理标记
  {
   var errorMsg = string.Empty;
   if (context.Response.StatusCode == 500 && exception != null)
   {
   errorMsg = $"{exceptionStatusCodeDic[context.Response.StatusCode]}\r\n{(exception.InnerException != null ? exception.InnerException.Message : exception.Message)}";
   }
   else
   {
   errorMsg = exceptionStatusCodeDic[context.Response.StatusCode];
   }
   exception = new Exception(errorMsg);
  }

  if (exception != null)
  {
   var handleType = _option.HandleType;
   if (handleType == CustomExceptionHandleType.Both) //根据Url关键字决定异常处理方式
   {
   var requestPath = context.Request.Path;
   handleType = _option.JsonHandleUrlKeys != null && _option.JsonHandleUrlKeys.Count(
    k => context.Request.Path.StartsWithSegments(k, StringComparison.CurrentCultureIgnoreCase)) > 0 ?
    CustomExceptionHandleType.JsonHandle :
    CustomExceptionHandleType.PageHandle;
   }
   
   if (handleType == CustomExceptionHandleType.JsonHandle)
   await JsonHandle(context, exception);
   else
   await PageHandle(context, exception, _option.ErrorHandingPath);
  }
  }
 }

 /// <summary>
 /// 统一格式响应类
 /// </summary>
 /// <param name="ex"></param>
 /// <returns></returns>
 private ApiResponse GetApiResponse(Exception ex)
 {
  return new ApiResponse() { IsSuccess = false, Message = ex.Message };
 }

 /// <summary>
 /// 处理方式：返回Json格式
 /// </summary>
 /// <param name="context"></param>
 /// <param name="ex"></param>
 /// <returns></returns>
 private async Task JsonHandle(HttpContext context, Exception ex)
 {
  var apiResponse = GetApiResponse(ex);
  var serialzeStr = JsonConvert.SerializeObject(apiResponse);
  context.Response.ContentType = "application/json";
  await context.Response.WriteAsync(serialzeStr, Encoding.UTF8);
 }

 /// <summary>
 /// 处理方式：跳转网页
 /// </summary>
 /// <param name="context"></param>
 /// <param name="ex"></param>
 /// <param name="path"></param>
 /// <returns></returns>
 private async Task PageHandle(HttpContext context, Exception ex, PathString path)
 {
  context.Items.Add("Exception", ex);
  var originPath = context.Request.Path;
  context.Request.Path = path; //设置请求页面为错误跳转页面
  try
  {
  await _next(context); 
  }
  catch { }
  finally
  {
  context.Request.Path = originPath; //恢复原始请求页面
  }
 }

public static class CustomExceptionMiddleWareExtensions
 {

 public static IApplicationBuilder UseCustomException(this IApplicationBuilder app, CustomExceptionMiddleWareOption option)
 {
  return app.UseMiddleware<CustomExceptionMiddleWare>(option);
 }
 }

 app.UseCustomException(new CustomExceptionMiddleWareOption(
   handleType: CustomExceptionHandleType.Both, //根据url关键字决定处理方式
   jsonHandleUrlKeys: new PathString[] { "/api" },
   errorHandingPath: "/home/error"));