I want to wrap all my http responses.
For example we have an action which returns some JSON data:
public IActionResult Get()
{
var res = new
{
MessageBody = "Test",
SomeData = 1
};
return Ok(res);
}
I want my response looks like:
{
"StatusCode":200,
"Result":
{
"MessageBody ":"Test",
"SomeData":1
}
}
If there is error then response must contain ErrorMessage field in a response.
In the mvc 5 I used the DelegationHandler, but in the asp.net core this class is not implemented. Now, we have to use middlewares.
This is code for mvc 5:
public class WrappingHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var response = await base.SendAsync(request, cancellationToken);
return BuildApiResponse(request, response);
}
private static HttpResponseMessage BuildApiResponse(HttpRequestMessage request, HttpResponseMessage response)
{
object content;
string errorMessage = null;
if (response.TryGetContentValue(out content) && !response.IsSuccessStatusCode)
{
HttpError error = content as HttpError;
if (error != null)
{
content = null;
errorMessage = error.Message;
#if DEBUG
errorMessage = string.Concat(errorMessage, error.ExceptionMessage, error.StackTrace);
#endif
}
}
var newResponse = request.CreateResponse(response.StatusCode, new ApiResponse(response.StatusCode, content, errorMessage));
foreach (var header in response.Headers)
{
newResponse.Headers.Add(header.Key, header.Value);
}
return newResponse;
}
}
and, a middleware for asp.net core. There are no TryGetContentValue, HttpError and other stuff in asp.net core. So, I am trying to read response body first:
public class FormatApiResponseMiddleware
{
private readonly RequestDelegate _next;
public FormatApiResponseMiddleware(RequestDelegate next)
{
_next = next;
}
private bool IsSuccessStatusCode(int statusCode)
{
return (statusCode >= 200) && (statusCode <= 299);
}
public async Task Invoke(HttpContext context)
{
object content = null;
string errorMessage = null;
if (!IsSuccessStatusCode(context.Response.StatusCode))
{
content = null;
//how to get error
}
var body= context.Response.Body;
}
}
But, Body stream has CanRead equal false and I get error that stream cannot be read. How to properly wrap response?
I suggest using ExceptionHandlerMiddleware as a template/sample on how your middleware should be implemented.
For example, you should be aware about case, when response has already started
// We can't do anything if the response has already started, just abort.
if (context.Response.HasStarted)
{
_logger.LogWarning("The response has already started, the error handler will not be executed.");
throw;
}
or don't forget to clear current response, if you want to replace it:
context.Response.Clear();
Moreover, maybe you will find useful just to reuse it, and implement your own error handler instead of a full middleware. That way you can send a custom JSON error to the client. For that, define a class that will represent your custom error:
public class ErrorDto
{
public int Code { get; set; }
public string Message { get; set; }
// other fields
public override string ToString()
{
return JsonConvert.SerializeObject(this);
}
}
Then register an exception handler middleware in the Configure method. Pay attention to the order in which the middleware is registered, and make sure it’s registered before MVC for example:
app.UseExceptionHandler(errorApp =>
{
errorApp.Run(async context =>
{
context.Response.StatusCode = 500; // or another Status
context.Response.ContentType = "application/json";
var error = context.Features.Get<IExceptionHandlerFeature>();
if (error != null)
{
var ex = error.Error;
await context.Response.WriteAsync(new ErrorDto()
{
Code = 1, //<your custom code based on Exception Type>,
Message = ex.Message // or your custom message
// … other custom data
}.ToString(), Encoding.UTF8);
}
});
});
Related
I need to sent custom exceptions message to client.
I have the following code:
in Startup.cs ConfigureServices method
services.AddGrpc(options => options.Interceptors.Add<ErrorInterceptor>());
in ErrorInterceptor.cs
public override async Task<TResponse> UnaryServerHandler<TRequest, TResponse>(TRequest request, ServerCallContext context, UnaryServerMethod<TRequest, TResponse> continuation)
{
try
{
return await continuation(request, context);
}
catch (ValidationException validationExc)
{
await WriteResponseHeadersAsync(StatusCode.InvalidArgument, translation =>
translation.GetEnumTranslation(validationExc.Error, validationExc.Parameters));
}
catch (Exception)
{
await WriteResponseHeadersAsync(StatusCode.Internal, translation =>
translation.GetEnumTranslation(HttpStatusCode.InternalServerError));
}
return default;
Task WriteResponseHeadersAsync(StatusCode statusCode, Func<ITranslationService, string> getMessage)
{
var httpContext = context.GetHttpContext();
var translationService = httpContext.RequestServices.GetService<ITranslationService>();
var errorMessage = getMessage(translationService);
var responseHeaders = new Metadata
{
{ nameof(errorMessage) , errorMessage },//1) can see in browser's devTools, but not in the code
{ "content-type" , errorMessage },//2) ugly, but works
};
context.Status = new Status(statusCode, errorMessage);//3) not working
return context.WriteResponseHeadersAsync(responseHeaders);//4) alternative?
}
}
in mask-http.service.ts
this.grpcClient.add(request, (error, reply: MaskInfoReply) => {
this.grpcBaseService.handleResponse<MaskInfoReply.AsObject>(error, reply, response => {
const mask = new Mask(response.id, response.name);
callback(mask);
});
});
in grpc-base.service.ts
handleResponse<T>(error: ServiceError,
reply: {
toObject(includeInstance?: boolean): T;
},
func: (response: T) => void) {
if (error) {
const errorMessage = error.metadata.headersMap['content-type'][0];
this.toasterService.openSnackBar(errorMessage, "Ok");
console.error(error);
return;
}
const response = reply.toObject();
func(response);
}
I wanted to send error using Status (comment 3), but it doesn't get changed
I wonder if there is an alternative way to send it not in response headers (comment 4)
I tried to add custom response header (comment 1), but the only one I received in client code was 'content-type' so I decided to overwrite it (comment 2)
I hit the same dead end recently and decided to do it this way:
Create an error model:
message ValidationErrorDto {
// A path leading to a field in the request body.
string field = 1;
// A description of why the request element is bad.
string description = 2;
}
message ErrorSynopsisDto {
string traceTag = 1;
repeated ValidationErrorDto validationErrors = 2;
}
Create an extension for the error model that serializes the object to JSON:
using Newtonsoft.Json;
using Newtonsoft.Json.Serialization;
public static class ErrorSynopsisDtoExtension
{
public static string ToJson(this ErrorSynopsisDto errorSynopsisDto) =>
JsonConvert.SerializeObject(
errorSynopsisDto,
new JsonSerializerSettings
{
ContractResolver = new CamelCasePropertyNamesContractResolver()
});
}
Create a custom exception that encapsulates error model:
public class OperationException : Exception
{
private readonly List<ValidationErrorDto> validationErrors = new();
public bool HasValidationErrors => this.validationErrors.Count > 0;
public OperationException(string traceTag) : base
(
new ErrorSynopsisDto
{
TraceTag = traceTag
}.ToJson() // <- here goes that extension
) => ErrorTag = traceTag;
public OperationException(
string traceTag,
List<ValidationErrorDto> validationErrors
) : base
(
new ErrorSynopsisDto
{
TraceTag = traceTag,
ValidationErrors = { validationErrors }
}.ToJson() // <- here goes that extension again
)
{
ErrorTag = traceTag;
this.validationErrors = validationErrors;
}
}
Throw custom exception from service call handlers:
throw new OperationException(
"MY_CUSTOM_VALIDATION_ERROR_CODE",
// the following block can be simplified with a mapper, for reduced boilerplate
new()
{
new()
{
Field = "Profile.FirstName",
Description = "Is Required."
}
}
);
And lastly, the exception interceptor:
public class ExceptionInterceptor : Interceptor
{
private readonly ILogger<ExceptionInterceptor> logger;
public ExceptionInterceptor(ILogger<ExceptionInterceptor> logger) => this.logger = logger;
public override async Task<TResponse> UnaryServerHandler<TRequest, TResponse>(
TRequest request,
ServerCallContext context,
UnaryServerMethod<TRequest, TResponse> continuation
)
{
try
{
return await continuation(request, context);
}
catch (OperationException ex)
{
this.logger.LogError(ex, context.Method);
var httpContext = context.GetHttpContext();
if (ex.HasValidationErrors)
{
httpContext.Response.StatusCode = StatusCodes.Status400BadRequest;
}
else
{
httpContext.Response.StatusCode = StatusCodes.Status500InternalServerError;
}
throw;
}
catch (Exception ex)
{
this.logger.LogError(ex, context.Method);
var httpContext = context.GetHttpContext();
httpContext.Response.StatusCode = StatusCodes.Status500InternalServerError;
var opEx = new OperationException("MY_CUSTOM_INTERNAL_ERROR_CODE");
throw new RpcException(
new Status(
StatusCode.Internal,
opEx.Message
)
);
}
}
}
On the TypeScript-based frontend, I simply catch RPC errors and hydrate the message like this:
JSON.parse(err.message ?? {}) as ErrorSynopsisDto
I have an ASP.NET Core API calling a second API.
I throw an exception in my services layer, if there is an error from the second API:
var response = await httpClient.SendAsync(request); //call second API
if (!response.IsSuccessStatusCode)
{
//return HTTP response with StatusCode = X, if response.StatusCode == X
throw new HttpRequestException(await response.Content.ReadAsStringAsync());
//this always returns 400
}
How can I throw an exception that will return a response with the same status code from the second API call?
If I use HttpRequestException it will always return 400, even if the response object had StatusCode = 500.
EDIT:
The first API endpoint looks like this:
public async Task<ActionResult<HttpResponseMessage>> CreateTenancy([FromBody]TenancyRequest tenancy)
{
//Make some calls...
return Created(string.Empty, new { TenancyID = newTenancyExternalId });
}
The second API endpoint looks like this:
[HttpPost]
public IHttpActionResult CreateTenancy([FromBody]TenancyDTO tenancyDTO)
{
var tenancy = GetTenancy();
return Created(string.Empty, tenancy);
}
I've tried using throw new HttpResponseException(response); but this removes the descriptive Exception message, the payload ends up like this:
{
"Code": 500,
"CorrelationId": "2df08016-e5e3-434a-9136-6824495ed907",
"DateUtc": "2020-01-30T02:02:48.4428978Z",
"ErrorMessage": "Processing of the HTTP request resulted in an exception. Please see the HTTP response returned by the 'Response' property of this exception for details.",
"ErrorType": "InternalServerError"
}
I'd like to keep the ErrorMessage value in the original payload:
{
"Code": 400,
"CorrelationId": "ff9466b4-8c80-4dab-b5d7-9bba1355a567",
"DateUtc": "2020-01-30T03:05:13.2397543Z",
"ErrorMessage": "\"Specified cast is not valid.\"",
"ErrorType": "BadRequest"
}
The end goal is to have this returned:
{
"Code": 500,
"CorrelationId": "ff9466b4-8c80-4dab-b5d7-9bba1355a567",
"DateUtc": "2020-01-30T03:05:13.2397543Z",
"ErrorMessage": "\"Specified cast is not valid.\"",
"ErrorType": "InternalServerError"
}
I tried something simple as changing the return type of the API endpoint and returning the object as it when there is an error. Otherwise, build your own HttpResponseMessage and return that. This snippet below uses text but you can use a serializer to serialize other content if you have.
public async Task<HttpResponseMessage> Test(string str)
{
var httpClient = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Get, $"myAPI that returns different errors 400, 404, 500 etc based on str");
var response = await httpClient.SendAsync(request);
if (!response.IsSuccessStatusCode)
return response;
// do something else
return new HttpResponseMessage(System.Net.HttpStatusCode.OK) { Content = new StringContent("Your Text here") };
}
Other approach of using Filters
The other approach of using IHttpActionResult as your return type, you can use Filters to conform all your HttpResponseMessages to IHttpActionResult.
Filter: Create a separate cs file and use this filter definition.
public class CustomObjectResponse : IHttpActionResult
{
private readonly object _obj;
public CustomObjectResponse(object obj)
{
_obj = obj;
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
HttpResponseMessage response = _obj as HttpResponseMessage;
return Task.FromResult(response);
}
}
and in your API, you would use your filter like so,
public async Task<IHttpActionResult> Test(string str)
{
var httpClient = new HttpClient();
var request = new HttpRequestMessage(HttpMethod.Get, $"http://localhost:4500/api/capacity/update-mnemonics/?mnemonic_to_update={str}");
var response = await httpClient.SendAsync(request);
if (!response.IsSuccessStatusCode)
return new CustomObjectResponse(response);
// Other Code here
// Return Other objects
KeyValuePair<string, string> testClass = new KeyValuePair<string, string>("Sheldon", "Cooper" );
return new OkWithObjectResult(testClass);
// Or Return Standard HttpResponseMessage
return Ok();
}
You could simply make your API call and copy its response code into something compatible with IStatusCodeActionResult.
An alternative s to throw a custom exception. Create something like
public class ApiCallException : Exception
{
public APiCallException(int statusCode, ...)
{
ApiStatusCode = statusCode;
}
int ApiStatusCode { get; }
...
}
and copy over the status code from your API result, and then throw the exception.
var response = await httpClient.SendAsync(request); //call second API
if (!response.IsSuccessStatusCode)
{
var content = await response.Content.ReadAsStringAsync();
throw new ApiCallException(500, content);
}
You can then register an exception filter to deal with the result when calling AddMvc.
services.AddMvc(options => options.Filters.Add<ExceptionFilter>());
where ExceptionFilter could be something like
public class ExceptionFilter : IExceptionFilter
{
// ...
public void OnException(ExceptionContext context)
{
if (context.Exception is ApiCallException ace)
{
var returnObject = CreateReturnObjectSomehow();
context.Result = new ObjectResult(returnObject) { StatusCode = ace.StatusCode };
}
else
{
// do something else
}
}
}
Thanks Jawad and Kit for providing great answers which helped me work out the solution below:
Turns out there was some middleware handling the exception:
public async Task Invoke(HttpContext httpContext)
{
try
{
await _next(httpContext);
}
catch (Exception exception)
{
if (httpContext.Response.HasStarted) throw;
var statusCode = ConvertExceptionToHttpStatusCode(exception);
httpContext.Response.Clear();
httpContext.Response.StatusCode = (int)statusCode;
httpContext.Response.ContentType = "application/json";
if (statusCode != HttpStatusCode.BadRequest)
{
_logger.Error(exception, "API Error");
}
await httpContext.Response.WriteAsync(JsonConvert.SerializeObject(new Error(statusCode, httpContext.Request.CorrelationId(), exception.Message, statusCode.ToString())));
}
}
The Error class looks like this:
public class Error
{
public int Code { get; }
public Guid? CorrelationId { get; }
public DateTime DateUtc { get; }
public string ErrorMessage { get; }
public string ErrorType { get; }
public Error(HttpStatusCode code, Guid? correlationId, string errorMessage, string errorType)
{
Code = (int)code;
CorrelationId = correlationId;
DateUtc = DateTime.UtcNow;
ErrorMessage = errorMessage;
ErrorType = errorType;
}
}
I created this class:
public class ApiCallException : Exception
{
public int StatusCode { get; }
public override string Message { get; }
public ApiCallException(int statusCode, string message)
{
StatusCode = statusCode;
Message = message;
}
}
Then updated my original code to have this:
if (!response.IsSuccessStatusCode)
{
throw new ApiCallException((int)response.StatusCode, await response.Content.ReadAsStringAsync());
}
In ASP.net Core 2.1, I want to return a Json response along with Status code 415 instead of just 415 returned by default.
To achieve this I am using a resource filter:
public class MediaTypeResouceFilter : Attribute, IResourceFilter
{
public void OnResourceExecuting(ResourceExecutingContext context)
{
}
public void OnResourceExecuted(ResourceExecutedContext context)
{
if (context.HttpContext.Response.StatusCode == 415)
{
context.Result = new ContentResult() { StatusCode = 415, Content = JsonConvert.SerializeObject(myResponse), ContentType = "application/json" };
}
}
}
In debugging, I see that context.Result is being overrided successfully but postman gets only 415 with no Json response.
In case I put:
context.Result = new ContentResult() { StatusCode = 415, Content = JsonConvert.SerializeObject(myResponse), ContentType = "application/json" };
inside OnResourceExecuting instead of OnResourceExecuted, it works as I wish but the thing is that I can't check for status code before executing resource.
Any ideas on why this is happening?
can you try this?
public class MediaTypeResouceFilter : Attribute, IResourceFilter
{
public void OnResourceExecuting(ResourceExecutingContext context)
{
}
public void OnResourceExecuted(ResourceExecutedContext context)
{
if (context.HttpContext.Response.StatusCode == 415)
{
var jsonString = JsonConvert.SerializeObject(new { data = "this is custom message" });
byte[] data = Encoding.UTF8.GetBytes(jsonString);
context.HttpContext.Response.Body.WriteAsync(data, 0, data.Length);
}
}
}
Then you can get a 415 Status Code and body data is: {"data":"this is custom message"}
Actually OnResourceExecuted fires too late but you can modify the body for your custom message
I think using the middleware component is a good choise. This is the Invoke method of the middleware:
public async Task Invoke(HttpContext context) {
Exception exception = null;
try {
await _next(context);
}
catch (Exception e) {
exception = e;
//try handling exception stuff...
}
//try handling 415 code stuff...
if(context.Response.StatusCode==415){
var yourJsonObj = new { Blah = "blah..." };
string result = JsonConvert.SerializeObject(yourJsonObj);
//context.Response.StatusCode = 200; //You can change the StatusCode here
context.Response.ContentType = "application/json";
await context.Response.WriteAsync(result);
}
}
See the workflow by Microsoft :
The method of IResourceFilter::OnResourceExecuted(ResourceExecutedContext context) runs after the Result execution. Since the result execution has already finished, you can make no change to result.
I have an ASP.NET Core 1.0 Web API application and trying to figure out how to pass the exception message to the client if a function that my controller is calling errors out.
I have tried so many things, but nothing implements IActionResult.
I don't understand why this isn't a common thing that people need. If there truthfully is no solution can someone tell me why?
I do see some documentation out there using HttpResponseException(HttpResponseMessage), but in order to use this, I have to install the compat shim. Is there a new way of doing these things in Core 1.0?
Here is something I have been trying with the shim but it isn't working:
// GET: api/customers/{id}
[HttpGet("{id}", Name = "GetCustomer")]
public IActionResult GetById(int id)
{
Customer c = _customersService.GetCustomerById(id);
if (c == null)
{
var response = new HttpResponseMessage(HttpStatusCode.NotFound)
{
Content = new StringContent("Customer doesn't exist", System.Text.Encoding.UTF8, "text/plain"),
StatusCode = HttpStatusCode.NotFound
};
throw new HttpResponseException(response);
//return NotFound();
}
return new ObjectResult(c);
}
When the HttpResponseException is thrown, I look on the client and can't find the message I am sending anything in the content.
Here is an simple error DTO class
public class ErrorDto
{
public int Code {get;set;}
public string Message { get; set; }
// other fields
public override string ToString()
{
return JsonConvert.SerializeObject(this);
}
}
And then using the ExceptionHandler middleware:
app.UseExceptionHandler(errorApp =>
{
errorApp.Run(async context =>
{
context.Response.StatusCode = 500; // or another Status accordingly to Exception Type
context.Response.ContentType = "application/json";
var error = context.Features.Get<IExceptionHandlerFeature>();
if (error != null)
{
var ex = error.Error;
await context.Response.WriteAsync(new ErrorDto()
{
Code = <your custom code based on Exception Type>,
Message = ex.Message // or your custom message
// other custom data
}.ToString(), Encoding.UTF8);
}
});
});
Yes it is possible to change the status code to whatever you need:
In your CustomExceptionFilterAttribute.cs file modify the code as follows:
public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
public override void OnException(ExceptionContext context)
{
var exception = context.Exception;
context.Result = new ContentResult
{
Content = $"Error: {exception.Message}",
ContentType = "text/plain",
// change to whatever status code you want to send out
StatusCode = (int?)HttpStatusCode.BadRequest
};
}
}
That's pretty much it.
If you have custom exceptions, then you can also check for them when grabbing the thrown exception from the context. Following on from that you can then send out different HTTP Status Codes depdending on what has happened in your code.
Hope that helps.
You can create a custom Exception Filter like below
public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
public override void OnException(ExceptionContext context)
{
var exception = context.Exception;
context.Result = new JsonResult(exception.Message);
}
}
Then apply the above attribute to your controller.
[Route("api/[controller]")]
[CustomExceptionFilter]
public class ValuesController : Controller
{
// GET: api/values
[HttpGet]
public IEnumerable<string> Get()
{
throw new Exception("Suckers");
return new string[] { "value1", "value2" };
}
}
Rather than raising and catching an exception, how about you simplify your action to:
// GET: api/customers/{id}
[HttpGet("{id}", Name = "GetCustomer")]
public IActionResult GetById(int id)
{
var customer = _customersService.GetCustomerById(id);
if (customer == null)
{
return NotFound("Customer doesn't exist");
}
return Ok(customer);
}
I wrote a blog post with some more options such as returning a JSON object instead of text.
Maybe that is helpful. You can return just object and sent for example a BadRequest (HTTP CODE: 400) with your custom object as actual parameter (I just used an interpolated string here) but you can put in anything.
In your client side you can catch that error situation for example with an AJAX error handler.
// GET: api/TruckFahrerGeoData
[HttpGet]
public object GetTruckFahrerGeoData()
{
var truckFahrerGeoDataItems = new List<TruckFahrerGeoDataViewModel>();
var geodataItems = _context.TruckFahrerGeoData;
foreach (var truckFahrerGeoData in geodataItems)
{
GeoTelemetryData geoTelemetryData = JsonConvert.DeserializeObject<GeoTelemetryData>(truckFahrerGeoData.TelemetryData);
if (geoTelemetryData == null)
{
return BadRequest($"geoTelemetryData null for id: {truckFahrerGeoData.Id}");
}
TruckFahrerGeoDataViewModel truckFahrerGeoDataViewModel = new TruckFahrerGeoDataViewModel
{
Speed = geoTelemetryData.Speed,
Accuracy = geoTelemetryData.Accuracy,
TruckAppId = geoTelemetryData.Activity.TruckAppId,
TruckAuftragStatusId = geoTelemetryData.Activity.TruckAuftragStatusId,
ClId = geoTelemetryData.Activity.ClId,
TruckAuftragLaufStatusId = geoTelemetryData.Activity.TruckAuftragLaufStatusId,
TaskId = geoTelemetryData.Activity.TaskId,
TruckAuftragWorkflowStatusId = geoTelemetryData.Activity.TruckAuftragWorkflowStatusId
};
truckFahrerGeoDataItems.Add(truckFahrerGeoDataViewModel);
}
return truckFahrerGeoDataItems;
}
Or an even more cleaner way with IActionResult like that way:
// GET: api/TruckFahrerGeoData
[HttpGet]
public IActionResult GetTruckFahrerGeoData()
{
var truckFahrerGeoDataItems = new List<TruckFahrerGeoDataViewModel>();
var geodataItems = _context.TruckFahrerGeoData;
foreach (var truckFahrerGeoData in geodataItems)
{
GeoTelemetryData geoTelemetryData = JsonConvert.DeserializeObject<GeoTelemetryData>(truckFahrerGeoData.TelemetryData);
if (geoTelemetryData == null)
{
return BadRequest($"geoTelemetryData null for id: {truckFahrerGeoData.Id}");
}
TruckFahrerGeoDataViewModel truckFahrerGeoDataViewModel = new TruckFahrerGeoDataViewModel
{
Speed = geoTelemetryData.Speed,
Accuracy = geoTelemetryData.Accuracy,
TruckAppId = geoTelemetryData.Activity.TruckAppId,
TruckAuftragStatusId = geoTelemetryData.Activity.TruckAuftragStatusId,
ClId = geoTelemetryData.Activity.ClId,
TruckAuftragLaufStatusId = geoTelemetryData.Activity.TruckAuftragLaufStatusId,
TaskId = geoTelemetryData.Activity.TaskId,
TruckAuftragWorkflowStatusId = geoTelemetryData.Activity.TruckAuftragWorkflowStatusId
};
truckFahrerGeoDataItems.Add(truckFahrerGeoDataViewModel);
}
return Ok(truckFahrerGeoDataItems);
}
Late to the party but refining the answer .
Define your error response class with minimum below attributes
using Microsoft.AspNetCore.Http;
public class ErrorResponse
{
private readonly RequestDelegate next;
public ErrorResponse(RequestDelegate next)
{
this.next = next;
}
public async Task Invoke(HttpContext context )
{
try
{
await next(context);
}
catch (Exception ex)
{
await HandleExceptionAsync(context, ex);
}
}
private static Task HandleExceptionAsync(HttpContext context, Exception ex)
{
var code = HttpStatusCode.InternalServerError;
string result = string.Empty;
object data = new object();
if (ex is ForbiddenException)
{
code = HttpStatusCode.Forbidden;
result = JsonConvert.SerializeObject(new Response<object>(Status.Forbidden(ex.Message), data));
}
else if(ex is BadRequestException){
code = HttpStatusCode.BadRequest;
result = JsonConvert.SerializeObject(new Response<object>(Status.BadRequest(ex.Message), data));
}
else if (ex is NotFoundException)
{
code = HttpStatusCode.NotFound;
result = JsonConvert.SerializeObject(new Response<object>(Status.NotFound(ex.Message), data));
}
else if (ex is UnauthorizedException)
{
code = HttpStatusCode.Unauthorized;
result = JsonConvert.SerializeObject(new Response<object>(Status.Unauthorized(ex.Message), data));
}
else
{
result = JsonConvert.SerializeObject(new Response<object>(Status.InternalServerError(ex.Message), data));
}
context.Response.ContentType = "application/json";
context.Response.StatusCode = (int)code;
return context.Response.WriteAsync(result);
}
}
Next use this class as middleware in startup.cs class
app.UseHttpsRedirection();
app.UseMiddleware(typeof(ErrorResponse));
Now each request and response will go through this class,if an error occurs then error code will be set to true with error code. A sample response like below
data: {}
status: {
code: 404
error: true
message: "No employee data found"
type: "Not Found"
}
I had the same problem and after some research, I found out I could use HttpClient to call my API and read the response easily. HttpClient does not throw any error when the HTTP response contains an error code, but it sets the IsSuccessStatusCode property to false.
This is my function using the HttpClient. I call this from my controller.
public static async Task<HttpResponseMessage> HttpClientPost(string header, string postdata, string url)
{
string uri = apiUrl + url;
using (var client = new HttpClient())
{
//client.BaseAddress = new Uri(uri);
client.DefaultRequestHeaders.Accept.Clear();
client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", header);
HttpResponseMessage response = await client.PostAsync(uri, new StringContent(postdata));
return response;
}
}
This is my controller code, where I call the function and read the response and determine whether I have an error or not and respond accordingly. Note that I am checking the IsSuccessStatusCode.
HttpResponseMessage response;
string url = $"Setup/AddDonor";
var postdata = JsonConvert.SerializeObject(donor);
response = await ApiHandler.HttpClientPost(HttpContext.Session.GetString(tokenName), postdata, url);
//var headers = response.Headers.Concat(response.Content.Headers);
var responseBody = await response.Content.ReadAsStringAsync();
if (response.IsSuccessStatusCode)
{
tnxresult = JsonConvert.DeserializeObject<TnxResult>(AppFunctions.CleanResponse(responseBody));
return Json(new
{
ok = true,
message = tnxresult.Message,
statusCode = tnxresult.StatusCode
});
}
else
{
ApiError rs = JsonConvert.DeserializeObject<ApiError>(AppFunctions.CleanResponse(responseBody));
return Json(new
{
ok = false,
message = rs.Message,
statusCode = rs.StatusCode
});
}
My API returns error messages in JSON. If the call is successful, I am packing the response in JSON too.
The crucial line of code is this one...
var responseBody = await response.Content.ReadAsStringAsync();
It serializes the HTTP content to a string as an asynchronous operation.
After that I can convert my JSON string to an object and access the error/success message and the Status Code too.
I'm looking at the documentation of WebAPI 2, and i'm severely disappointed with the way the action results are architected. I really hope there is a better way.
So documentation says I can return these:
**void** Return empty 204 (No Content)
**HttpResponseMessage** Convert directly to an HTTP response message.
**IHttpActionResult** Call ExecuteAsync to create an HttpResponseMessage, then convert to an HTTP response message.
**Other type** Write the serialized return value into the response body; return 200 (OK).
I don't see a clean way to return an array of items with custom HTTP status code, custom headers and with auto negotiated content though.
What I would like to see is something like
public HttpResult<Item> Post()
{
var item = new Item();
var result = new HttpResult<Item>(item, HttpStatusCode.Created);
result.Headers.Add("header", "header value");
return result;
}
This way I can glance over a method and immediately see whats being returned, and modify status code and headers.
The closest thing I found is NegotiatedContentResult<T>, with weird signature (why does it need an instance of controller?), but there's no way to set custom headers?
Is there a better way ?
The following code should give you everything you want:
[ResponseType(typeof(Item))]
public IHttpActionResult Post()
{
var item = new Item();
HttpContext.Current.Response.AddHeader("Header-Name", "Header Value");
return Content(HttpStatusCode.Created, item);
}
... if you really need to return an array of items ...
[ResponseType(typeof(List<Item>))]
public IHttpActionResult Post()
{
var items = new List<Item>();
// Do something to fill items here...
HttpContext.Current.Response.AddHeader("Item-Count", items.Count.ToString());
return Content(HttpStatusCode.Created, items);
}
I don't think the designers of the web-api intended for controller methods to be fiddling with the headers.
The design pattern seems to be to use DelegatingHandler, ActionFilterAttribute and the ExecuteAsync overridable method of ApiController to handle authentication and response formatting.
So perhaps your logic for message content negotiation should be handled there ?
However if you definitely need to control headers from within your controller method you can do a little set-up to make it work.
To do so you can create your own DelegationHandler that forwards selected headers from your "Inner" response headers:
public class MessageHandlerBranding : DelegatingHandler {
protected async override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var response = await base.SendAsync(request, cancellationToken);
//If we want to forward headers from inner content we can do this:
if (response.Content != null && response.Content.Headers.Any())
{
foreach (var hdr in response.Content.Headers)
{
var keyUpr = hdr.Key.ToUpper(); //Response will not tolerate setting of some header values
if ( keyUpr != "CONTENT-TYPE" && keyUpr != "CONTENT-LENGTH")
{
string val = hdr.Value.Any() ? hdr.Value.FirstOrDefault() : "";
response.Headers.Add(hdr.Key, val);
}
}
}
//Add our branding header to each response
response.Headers.Add("X-Powered-By", "My product");
return response;
}
}
Then you register this handler in your web-api configuration, this is usually in the GlobalConfig.cs file.
config.MessageHandlers.Add(new MessageHandlerBranding());
You could also write your own custom class for the response object like this:
public class ApiQueryResult<T> : IHttpActionResult where T : class
{
public ApiQueryResult(HttpRequestMessage request)
{
this.StatusCode = HttpStatusCode.OK; ;
this.HeadersToAdd = new List<MyStringPair>();
this.Request = request;
}
public HttpStatusCode StatusCode { get; set; }
private List<MyStringPair> HeadersToAdd { get; set; }
public T Content { get; set; }
private HttpRequestMessage Request { get; set; }
public void AddHeaders(string headerKey, string headerValue)
{
this.HeadersToAdd.Add(new MyStringPair(headerKey, headerValue));
}
public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)
{
var response = this.Request.CreateResponse<T>(this.StatusCode, this.Content);
foreach (var hdr in this.HeadersToAdd)
{
response.Content.Headers.Add(hdr.key, hdr.value);
}
return Task.FromResult(response);
}
private class MyStringPair
{
public MyStringPair(string key, string value)
{
this.key = key;
this.value = value;
}
public string key;
public string value;
}
}
And use it like this in your controller:
[HttpGet]
public ApiQueryResult<CustomersView> CustomersViewsRow(int id)
{
var ret = new ApiQueryResult<CustomersView>(this.Request);
ret.Content = this.BLL.GetOneCustomer(id);
ret.AddHeaders("myCustomHkey","myCustomValue");
return ret;
}