in my webapi project I have a global exception handler and I want to set the status code 500 when an exception is uncaught and I want to set a custom message, but I don't know how to set that message. Here is my code:
public class MyExceptionHandler : IExceptionHandler
{
public Task HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
{
context.Result = new StatusCodeResult(HttpStatusCode.InternalServerError, context.Request);
return Task.FromResult<object>(null);
}
}
and the config is:
config.IncludeErrorDetailPolicy = IncludeErrorDetailPolicy.LocalOnly;
config.Services.Replace(typeof(IExceptionHandler), new MyExceptionHandler());
In postman the response body is empty and I just see the 500 error code. So how to set a message here?
Here is an example:
public class ExceptionFilter : ExceptionFilterAttribute
{
private TelemetryClient TelemetryClient { get; }
public ExceptionFilter(TelemetryClient telemetryClient)
{
TelemetryClient = telemetryClient;
}
public override void OnException(ExceptionContext context)
{
context.ExceptionHandled = true;
context.HttpContext.Response.Clear();
context.HttpContext.Response.StatusCode = (int) HttpStatusCode.InternalServerError;
context.Result = new JsonResult(new
{
error = context.Exception.Message
});
TelemetryClient.TrackException(context.Exception);
}
}
and you can use it in your startup - ConfigureService:
services.AddSingleton<ExceptionFilter>();
services.AddMvc(
options => { options.Filters.Add(services.BuildServiceProvider().GetService<ExceptionFilter>()); });
it will now also send exception to azure telemetry.
You can offcourse remove the telemetryclient and the methods :)
cheers!
Related
First of all a bit of background.
I am using .Net Framework 4.6.1, Microsoft.AspNet.WebApi 5.2.4 in Visual Studio 2017 Community.
My ApiController's implement endpoints which throw intended Exceptions for example if certain requirements are not met. I added global ExceptionFilterAttribute and ExceptionHandler to handle those Exceptions and to return a proper response.
The Exceptions are of a type which are inherited of System.Exception.
This is only working occasionally as intended. Every second or third or sometimes fifth (no real pattern) request the api server returns no response at all e.g. for example Postman says: "Could not get any response".
To test this I used the same endpoint with the same input.
Here are a few things I did to get a better idea of the problem:
I added exception logging to Global.asax (to catch First Chance Exceptions)
I subscribed to Global.asax Application_Error Event
I looked at the IIS logs
None of those got my closer to the issue. The exception was caught and logged in Global.asax like expected but no additional error or exception which could give me more info to my problem.
Here is my code:
I simplified the ApiController's function and removed the business logic.
[Route("test")]
[HttpGet]
public IHttpActionResult GetTest()
{
throw new ObjectAlreadyExistsException("test");
return ResponseFactory.CreateOkResponse(null);
}
public class ExceptionFilter : ExceptionFilterAttribute
{
public override void OnException(HttpActionExecutedContext context)
{
if (context.Exception is ObjectAlreadyExistsException)
{
context.Response = ResponseFactory.CreateErrorResponseMessage(context.Exception.Message, new Error("OBJECT_ALREADY_EXISTS_ERROR", context.Exception.Message));
}
else if (context.Exception is ObjectNotFoundException)
{
context.Response = ResponseFactory.CreateErrorResponseMessage(context.Exception.Message, new Error("OBJECT_NOT_FOUND_ERROR", context.Exception.Message));
}
base.OnException(context);
}
}
public class GlobalExceptionHandler : ExceptionHandler
{
private static readonly ILogger Log = new LoggerConfiguration()
.WriteTo.File(new CompactJsonFormatter(), Path.Combine(#Properties.Settings.Default.LOG_DIRECTORY, #"error.json"), rollOnFileSizeLimit: true, retainedFileCountLimit: 5, shared: true)
.Enrich.WithWebApiControllerName()
.Enrich.WithWebApiActionName()
.Enrich.WithWebApiRouteTemplate()
.Enrich.WithWebApiRouteData()
.Enrich.With(new AuthTokenEnricher())
.CreateLogger();
public override void Handle(ExceptionHandlerContext context)
{
if (context != null && context.Exception != null)
{
Log.Error("Unexpected Internal Server Error {Exception}", context.Exception);
}
context.Result = ResponseFactory.CreateErrorResponse(HttpStatusCode.InternalServerError, "Unexpected Internal Server Error", new Error("INTERNAL_SERVER_ERROR", "This request failed because of an unexpected server error."));
}
}
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
//Exception filters
config.Filters.Add(new ExceptionFilter());
config.Services.Replace(typeof(IExceptionHandler), new GlobalExceptionHandler());
// Web API routes
config.MapHttpAttributeRoutes();
}
}
public class ObjectAlreadyExistsException : Exception
{
public ObjectAlreadyExistsException(string message) : base(message)
{
}
public ObjectAlreadyExistsException(string message, Exception inner) : base(message, inner)
{
}
}
For now I put a workaround in place which looks like this:
[Route("test")]
[HttpGet]
public IHttpActionResult GetTest()
{
try
{
throw new ObjectAlreadyExistsException("test");
}
catch (Exception ex)
{
return CustomExceptionHandler.Handle(ex);
}
}
public class CustomExceptionHandler
{
private static readonly ILogger Log = new LoggerConfiguration()
.WriteTo.File(new CompactJsonFormatter(), Path.Combine(#Properties.Settings.Default.LOG_DIRECTORY, #"error.json"), rollOnFileSizeLimit: true, retainedFileCountLimit: 5, shared: true)
.Enrich.WithWebApiControllerName()
.Enrich.WithWebApiActionName()
.Enrich.WithWebApiRouteTemplate()
.Enrich.WithWebApiRouteData()
.Enrich.With(new AuthTokenEnricher())
.CreateLogger();
public static IHttpActionResult Handle(Exception ex)
{
IHttpActionResult result = null;
if (ex != null)
{
if (ex is ObjectAlreadyExistsException)
{
result = ResponseFactory.CreateErrorResponse(ex.Message, new Error("OBJECT_ALREADY_EXISTS_ERROR", ex.Message));
}
else if (ex is ObjectNotFoundException)
{
result = ResponseFactory.CreateErrorResponse(ex.Message, new Error("OBJECT_NOT_FOUND_ERROR", ex.Message));
}
}
if (result == null)
{
if (ex != null)
{
Log.Error("Unexpected Internal Server Error {Exception}", ex);
}
result = ResponseFactory.CreateErrorResponse(HttpStatusCode.InternalServerError, "Unexpected Internal Server Error", new Error("INTERNAL_SERVER_ERROR", "This request failed because of an unexpected server error."));
}
return result;
}
}
I would appreciate any ideas how to debug this or any suggestions to fix it.
Can you try inheriting from IHttpActionResult and use it as returning the exception from your GlobalExceptionHandler
private class ErrorMessageResult : IHttpActionResult
{
private readonly HttpResponseMessage _httpResponseMessage;
private HttpRequestMessage _request;
public ErrorMessageResult(HttpRequestMessage request, HttpResponseMessage httpResponseMessage)
{
_request = request;
_httpResponseMessage = httpResponseMessage;
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
return Task.FromResult(_httpResponseMessage);
}
}
and call it like,
public override void Handle(ExceptionHandlerContext context)
{
var result = new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content = new StringContent("Internal Server Error Occurred"),
ReasonPhrase = "Exception"
};
context.Result = new ErrorMessageResult(context.Request, result);
}
From GlobalExceptionHandler : ExceptionHandler
I'm developping a web API with ASP.NET Core and I'm trying to implement a custom error handling middleware so I can throw standard exceptions that can be converted into a JSON response with the appropriate HTTP Status code.
For example if I do:
throw new NotFoundApiException("The object was not found");
I need it to be converted into:
StatusCode: 404
ContentType: application/json
ResponseBody: {"error": "The object was not found"}
Here is my middleware:
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 (ApiException ex) {
await HandleExceptionAsync(context, ex);
}
}
private static Task HandleExceptionAsync(HttpContext context, ApiException exception)
{
var result = JsonConvert.SerializeObject(new { error = exception.Message });
context.Response.ContentType = "application/json";
context.Response.StatusCode = exception.httpStatusCode;
return context.Response.WriteAsync(result);
}
}
Exceptions
public class ApiException : System.Exception
{
private int _httpStatusCode = (int)HttpStatusCode.InternalServerError;
public ApiException() { }
public ApiException(string message): base(message) { }
public int httpStatusCode {
get { return this._httpStatusCode; }
}
}
public class NotFoundApiException : ApiException
{
private int _httpStatusCode = (int)HttpStatusCode.BadRequest;
public NotFoundApiException() { }
public NotFoundApiException(string message): base(message) { }
}
Startup
public void Configure(/*...*/)
{
loggerFactory.AddConsole();
app.UseMiddleware<ErrorHandlingMiddleware>();
app.UseMvc();
}
Controller action
[HttpGet("object/{guid}")]
public WebMessage Get(Guid guid)
{
throw new NotFoundApiException(string.Format("The object {0} was not found", guid));
//...
I can see the request entering my registered middleware but the exception is not catched and simply thrown as usual.
I'm suspecting a race condition or something similar, I don't know very much about them async functions actually.
Has someone got an idea why my exception is not catched ?
edit By continuing the execution with VisualStudio I can see the expected behavior: I'm finally getting my response.
Seems like the Exception is not really catched by the middleware but somehow processed afterwards.
My solution to this problem was to remove app.UseDeveloperExceptionPage(); in Startup.cs
In my case, I found that app.UseMiddleware<ExceptionHandlingMiddleware>(); should be at the top of Configure() method.
You can try also Exception filters.
(of course, filters are not so flexible like as error handling middleware, which is better in general case, but - at least for me - filters are working fine without any issues)
That's what I'm using:
public class ExceptionGlobalFilter : ExceptionFilterAttribute
{
private readonly ILogger logger;
public ExceptionGlobalFilter(ILoggerFactory lf)
{
logger = lf.CreateLogger("ExceptionGlobalFilter");
}
public override void OnException(ExceptionContext context)
{
var customObject = new CustomObject(context.Exception);
//TODO: Add logs
if (context.Exception is BadRequestException)
{
context.Result = new BadRequestObjectResult(customObject);
}
else if (context.Exception is NotFoundException)
{
context.Result = new NotFoundObjectResult(customObject);
}
else
{
context.Result = new OkObjectResult(customObject);
}
base.OnException(context);
}
public override async Task OnExceptionAsync(ExceptionContext context)
{
await base.OnExceptionAsync(context);
return;
}
}
Startup.cs:
services.AddMvc(config =>
{
config.Filters.Add(typeof(ExceptionGlobalFilter));
});
More info:
Introduction to Error Handling in ASP.NET Core
Exception filters
Filters
MVC Issue #5594
ExceptionHandlerMiddleware.cs
In my case app.UseDeveloperExceptionPage(); was written in the Startup after the exception handler middleware. The fix was simply by moving the exception handler middleware to be after it.
#Pierre, I have met the same issue here when using Middleware as the global exception handler. The issue was caused by my mistake to wrote an "async void" method, I have throwed an exception in the method named "NewException":
[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
// GET api/values
[HttpGet]
public async Task<IActionResult> Get()
{
NewException();
return Ok("<h1>Hi, Welcome！</h1>");
}
private async void NewException()
{
throw new InvalidOperationException("WTF");
}
The exception [InvalidOperationException("WTF")] will not be catching by the Middleware, if I change the code snippet to :
[Route("api/[controller]")]
[ApiController]
public class ValuesController : ControllerBase
{
// GET api/values
[HttpGet]
public async Task<IActionResult> Get()
{
await NewException();
return Ok("<h1>Hi, Welcome！</h1>");
}
private async Task NewException()
{
throw new InvalidOperationException("WTF");
}
The exception Middleware will catch it. Hope this help.
I am trying to figure out how to implement a Global Exception Handler in .NET Web Api 2.
I tried following the example set out by Microsoft here:
https://learn.microsoft.com/en-us/aspnet/web-api/overview/error-handling/web-api-global-error-handling
But when exception occured, it did nothing.
This is my code:
public class GlobalExceptionHandler : ExceptionHandler
{
public override void Handle(ExceptionHandlerContext context)
{
Trace.WriteLine(context.Exception.Message);
context.Result = new TextPlainErrorResult
{
Request = context.ExceptionContext.Request,
Content = "Oops! Sorry! Something went wrong." +
"Please contact support#testme.com so we can try to fix it."
};
}
private class TextPlainErrorResult : IHttpActionResult
{
public HttpRequestMessage Request { private get; set; }
public string Content { private get; set; }
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
var response =
new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content = new StringContent(Content),
RequestMessage = Request
};
return Task.FromResult(response);
}
}
}
Is there a better way (or more proper way) to implement a global exception handler?
Try adding this to your WebApiConfig
webConfiguration.Services.Replace(typeof(IExceptionHandler), new MyExceptionHandler()); // You have to use Replace() because only one handler is supported
webConfiguration.Services.Add(typeof(IExceptionLogger), new MyExceptionLogger()); // webConfiguration is an instance of System.Web.Http.HttpConfiguration
You missed
class GlobalExceptionHandler : ExceptionHandler
{
public override bool ShouldHandle(ExceptionHandlerContext context)
{
return true;
}
//...
}
See WebApi v2 ExceptionHandler not called
When ovveride the IExceptionHandler, the response does not reach the DelegatingHandler when a unexpected exception occurs. How can I fix this?
In webapi 2, I want to implement a audit logger for request and response messages. I also want to add a global exception handler. However, when I replace the IExceptionHandler with my custom implementation. the response never reaches the DelegatingHandler -on exception - And thus the audit for response is lost.
in WebApiConfig
// add custom audittrail logger
config.MessageHandlers.Add(new AuditLogHandler());
// replace global exception handeling
config.Services.Replace(typeof(IExceptionHandler), new WebAPiExceptionHandler());
Custom Exception Handler
public class WebAPiExceptionHandler : ExceptionHandler
{
//A basic DTO to return back to the caller with data about the error
private class ErrorInformation
{
public string Message { get; set; }
public DateTime ErrorDate { get; set; }
}
public override void Handle(ExceptionHandlerContext context)
{
context.Result = new ResponseMessageResult(context.Request.CreateResponse(HttpStatusCode.InternalServerError,
new ErrorInformation { Message = "Iets is misgegaan", ErrorDate = DateTime.UtcNow }));
}
}
Custom Auditlogger
public class AuditLogHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
if (request.Content != null)
{
var task = await request.Content.ReadAsStringAsync();
// .. code for loggign request
}
var result = await base.SendAsync(request, cancellationToken);
// .. code for logging response
// when I do not replace WebAPiExceptionHandler, code is reachred here
// When I Do use WebAPiExceptionHandler, code is not reached here
return result;
}
}
Code for throwing exception in webapi
public class Values_v2Controller : ApiController
{
public string Get(int id)
{
throw new Exception("haha");
}
}
Dont use ExceptionHandler as base class, implement interface IExceptionHandler
public class WebAPiExceptionHandler : IExceptionHandler
{
public Task HandleAsync(ExceptionHandlerContext context, CancellationToken cancellationToken)
{
var fout = new ErrorInformation
{
Message = "Iets is misgegaan"
, ErrorDate = DateTime.UtcNow
};
var httpResponse = context.Request.CreateResponse(HttpStatusCode.InternalServerError, fout);
context.Result = new ResponseMessageResult(httpResponse);
return Task.FromResult(0);
}
private class ErrorInformation
{
public string Message { get; set; }
public DateTime ErrorDate { get; set; }
}
}
The problem is that ExceptionHandler only executes Handle(ExceptionHandlerContext context) method if ShouldHandle(ExceptionHandlerContext context) returns true.
Overriding bool ShouldHandle(ExceptionHandlerContext context) to always return true fix the problem for me.
In my C# Web API, I'm trying to add a global exception handler. I've been using a custom global ExceptionFilterAttribute to handle the exception and return a HttpResponseMessage:
public override void OnException(HttpActionExecutedContext context)
{
...
const string message = "An unhandled exception was raised by the Web API.";
var httpResponseMessage = new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content = new StringContent(message),
ReasonPhrase = message
};
context.Response = httpResponseMessage;
}
This has worked fine for handling exceptions thrown at the controller level.
However, during development we had an error thrown from our OWIN startup file due to a database connection issue, however, a standard IIS exception was returned, instead of going through the global exception handler, and the full HTML was returned to our API consumer.
I've tried a few different approaches to catch exceptions thrown in my OWIN startup:
Custom ApiControllerActionInvoker:
public class CustomActionInvoker : ApiControllerActionInvoker
{
public override Task<HttpResponseMessage> InvokeActionAsync(HttpActionContext actionContext, CancellationToken cancellationToken)
{
var result = base.InvokeActionAsync(actionContext, cancellationToken);
if (result.Exception != null && result.Exception.GetBaseException() != null)
{
...
}
return result;
}
}
Custom ExceptionHandler:
public class CustomExceptionHandler : ExceptionHandler
{
public override void Handle(ExceptionHandlerContext context)
{
...
base.Handle(context);
}
public override bool ShouldHandle(ExceptionHandlerContext context)
{
return true;
}
}
Custom OwinMiddleware component:
public class CustomExceptionMiddleware : OwinMiddleware
{
public CustomExceptionMiddleware(OwinMiddleware next) : base(next)
{
}
public override async Task Invoke(IOwinContext context)
{
try
{
await Next.Invoke(context);
}
catch (Exception ex)
{
...
}
}
}
And finally just using Application_Error:
protected void Application_Error(object sender, EventArgs e)
{
...
}
But nothing seems to catch the exception.
Does anyone know of a way to catch the exception and return a HttpResponseMessage? Or if any of the approaches I've already tried should have worked?
Any help much appreciated.
I have an application that does this correctly. In my case I wrote a middleware class that always returns a message telling the caller that the service is unavailable because there was an error during startup. This class is called FailedSetupMiddleware in my solution. The outline of it looks like this:
public class FailedSetupMiddleware
{
private readonly Exception _exception;
public FailedSetupMiddleware(Exception exception)
{
_exception = exception;
}
public Task Invoke(IOwinContext context, Func<Task> next)
{
var message = ""; // construct your message here
return context.Response.WriteAsync(message);
}
}
In my Configuration class I have a try...catch block that configures the OWIN pipeline with only the FailedSetupMiddleware in the case where an exception was thrown during configuration.
My OWIN startup class looks like this:
[assembly: OwinStartup(typeof(Startup))]
public class Startup
{
public void Configuration(IAppBuilder app)
{
try
{
//
// various app.Use() statements here to configure
// OWIN middleware
//
}
catch (Exception ex)
{
app.Use(new FailedSetupMiddleware(ex).Invoke);
}
}
}