例外處理機制

目的 : 讓前端呼叫者可以顯示易懂的錯誤訊息

步驟 :

1. 自訂 ActionResult

public class CustomError : IActionResult

{

private readonly HttpStatusCode _status;

private readonly string _errorMessage;

public CustomError(HttpStatusCode status, string errorMessage)

{

_status = status;

_errorMessage = errorMessage;

}

public async Task ExecuteResultAsync(ActionContext context)

{

var objectResult = new ObjectResult(new

{

errorMessage = _errorMessage

})

{

StatusCode = (int)_status,

};

context.HttpContext.Features.Get<IHttpResponseFeature>().ReasonPhrase = _errorMessage;

await objectResult.ExecuteResultAsync(context);

}

}

2. 自訂 ExceptionFilter

public class BaseExceptionFilter : IExceptionFilter

{

private readonly IHostEnvironment _hostEnvironment;

public BaseExceptionFilter(IHostEnvironment hostEnvironment) =>

_hostEnvironment = hostEnvironment;

public void OnException(ExceptionContext context)

{

if (_hostEnvironment.IsDevelopment())

{

// 顯示英文訊息方便google

System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");

System.Threading.Thread.CurrentThread.CurrentUICulture = new System.Globalization.CultureInfo("en-US");

}

string controllerName = context.RouteData.Values["controller"].ToString();

string actionName = context.RouteData.Values["action"].ToString();

var request = context.HttpContext.Request;

var requestUrl = request.Scheme + "://" + request.Host + request.Path;

                var username = context.HttpContext.User?.Identity.Name;

System.Text.StringBuilder sb = new System.Text.StringBuilder();

sb.AppendLine("xxx發生未預期錯誤");

sb.AppendLine($"錯誤訊息: {context.Exception.詳細訊息()}");

sb.AppendLine($"堆疊追蹤: {context.Exception.StackTrace.Replace("<","＜").Replace(">","＞")}"); // 若使用skype 通知則不接受<和>

sb.AppendLine($"網址: {requestUrl}");

         sb.AppendLine($"系統使用者: {username}");

sb.AppendLine($"Controller: {controllerName}");

sb.AppendLine($"Action: {actionName}");

                if (_hostEnvironment.IsDevelopment()) {

                    // 直接顯示除錯訊息

                    context.Result = new CustomError(HttpStatusCode.InternalServerError, sb.ToString());

                }

                else {

                    // todo: 使用 skype、line、email 等方式發送除錯訊息給資訊人員

                     context.Result =  new CustomError(HttpStatusCode.InternalServerError, "發生未預期錯誤，請洽資訊部");

                }

}

}

3.1. 建立頂層 Controller，遇到未攔截的錯誤時透過自訂 ExceptionFilter 回傳自訂 ActionResult

[TypeFilter(typeof(BaseExceptionFilter))]

public class BaseController : ControllerBase

3.2. Controller Action 若要回傳錯誤則透過自訂ActionResult

ex. return new CustomError(HttpStatusCode.BadRequest, "請輸入收貨地址");

4. 前端顯示錯誤訊息

ex.

axios.interceptors.response.use(function (response) {

return response;

}, function (error) {

console.error(error);

if (error.response.status == 401) {

alert('登入逾時');

setTimeout(() => {

window.location.reload();

}, 2000);

}

else {

if (error.response.data.errorMessage) alert(error.response.data.errorMessage);

else alert(error.message);

}

return Promise.reject(error);

});

非 core 版後端寫法

public class BaseExceptionFilter : FilterAttribute, IExceptionFilter

{

public void OnException(ExceptionContext context)

{

// 顯示英文訊息方便google

System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");

System.Threading.Thread.CurrentThread.CurrentUICulture = new System.Globalization.CultureInfo("en-US");

string controllerName = context.RouteData.Values["controller"].ToString();

string actionName = context.RouteData.Values["action"].ToString();

var requestUrl = context.HttpContext.Request.Url.AbsoluteUri;

System.Text.StringBuilder sb = new System.Text.StringBuilder();

sb.AppendLine("xxx發生未預期錯誤");

sb.AppendLine($"錯誤訊息: {context.Exception.詳細訊息()}");

sb.AppendLine($"堆疊追蹤: {context.Exception.StackTrace.Replace("<", "＜").Replace(">", "＞")}");

sb.AppendLine($"網址: {requestUrl}");

sb.AppendLine($"系統使用者: {xxx}");

sb.AppendLine($"Controller: {controllerName}");

sb.AppendLine($"Action: {actionName}");

// todo: 使用 skype、line、email 等方式發送除錯訊息給資訊人員

context.ExceptionHandled = true;

context.HttpContext.Response.TrySkipIisCustomErrors = true;

context.HttpContext.Response.Write("發生未預期錯誤，請洽資訊部");

context.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError;

}

}

頂層Controller

[BaseExceptionFilter]

public class BaseController : Controller

{

  

}

※若要回傳可預期錯誤給使用者看，則用以下方式

async public Task<IHttpActionResult> xxxAsync()

{

if (xxx)

{

HttpContext.Current.Response.Write(xxx);

HttpContext.Current.Response.StatusCode = (int)System.Net.HttpStatusCode.BadRequest;

return default;

}