How to show custom error page in ServiceStack - exception

I have read through Error Handling, ServiceStack_Succinctly.pdf, ServiceStack 4 Cookbook and various SO questions and am still unable to get the following working.
I want a way to show my own "pretty" error page for any exception that is thrown in any of my services. If any exception is thrown I want to take the user to a friendly page that shows the error message without any information that "mere mortals" won't understand.
Ideally I want this while maintaining typed responses on my service requests, i.e. not
public object Get(GetOrder request)
{
return new GetOrderResponse()
{
...
}
}
but rather
public GetOrderResponse Get(GetOrder request)
{
return new GetOrderResponse()
{
...
}
}
I'd appreciate guidance on how to get this working or an example where this is done.
Thanks.

Have a look at the options for Fallback Error Pages e.g. you can display an /oops.cshtml Razor page with:
public override void Configure(Container container)
{
Plugins.Add(new RazorFormat()); //Register ServiceStack.Razor Plugin
this.GlobalHtmlErrorHttpHandler = new RazorHandler("/oops"),
}
Or for more fine-grained control, use IAppHost.CustomHttpHandlers for specifying custom HttpHandlers to use with specific error status codes, e.g.:
public override void Configure(Container container)
{
this.CustomHttpHandlers[HttpStatusCode.NotFound] =
new RazorHandler("/notfound");
this.CustomHttpHandlers[HttpStatusCode.Unauthorized] =
new RazorHandler("/login");
}

Related

How to make my Apex class return or "run" a JSON? using APEX REST

I am using the following code to generate a JSON for a Salesforce custom object called Resource Booking. How can I "run" the file (or call responseJSON) so that when I input the custom URL (in the first comment) it jumps to a page similar to this example web page? https://www.googleapis.com/customsearch/v1?json
Here is my code:
#RestResource(urlMapping='/demo/createTask/*') //endpoint definition > {Salesforce Base URL}/services/apexrest/demo/createTask/
global class ResourceBookingTransfer {
public List<Resource_Booking__c> resourceBookingList{get; set;}
public ResourceBookingTransfer(ApexPages.StandardController controller) {
//getResourceBookingList();
}
#HttpGet //HttpGet request
global static responseWrapper getResourceBookingList() {
responseWrapper responseJSON = new responseWrapper(); //responseWrapper object for API response
responseJSON.message = 'Hello World';
return responseJSON; //return the JSON response
//resourceBookingList = Database.query('SELECT Booking_ID__c, Booking_Name__c, Start_Date_Time__c, End_Date_Time__c, Resource__c FROM Resource_Booking__c');
}
//wrapper class for the response to an API request
global class responseWrapper {
global String message {get;set;} //message string
//constructor
global responseWrapper() {
this.message = '';
}
}
}
To just test it - it might be simplest to use https://workbench.developerforce.com. There's "REST explorer" menu in there. Your code should be available under resource similar to /services/apexrest/demo/createTask.
Why that url? Read https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_rest_code_sample_basic.htm
Once you're happy with this manual testing - you can try to do it from outside workbench. Workbench logs you in to SF and passed header with valid session id in the background. If you want to call your service from another website or mobile app - you need to perform login call first, get the session id and then run your code. There are several OAuth flows you can use to do this depending in what your app needs, maybe start with this one: https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/intro_understanding_username_password_oauth_flow.htm

Returning JSON Errors from Asp.Net MVC 6 API

I'm trying out building a web API with MVC 6. But when one of my controller methods throws an error, the content of the response is a really nicely formatted HTML page that would be very informative were this an MVC app. But since this is an API, I'd rather have some JSON returned instead.
Note: My setup is super basic right now, just setting:
app.UseStaticFiles();
app.UseIdentity();
// Add MVC to the request pipeline.
app.UseMvc();
I want to set this up universally. Is there a "right/best" way to set this up in MVC 6 for an API?
Thanks...
One way to achieve your scenario is to write an ExceptionFilter and in that capture the necessary details and set the Result to be a JsonResult.
// Here I am creating an attribute so that you can use it on specific controllers/actions if you want to.
public class CustomExceptionFilterAttribute : ExceptionFilterAttribute
{
public override void OnException(ExceptionContext context)
{
var exception = context.Exception;
context.Result = new JsonResult(/*Your POCO type having necessary details*/)
{
StatusCode = (int)HttpStatusCode.InternalServerError
};
}
}
You can add this exception filter to be applicable to all controllers.
Example:
app.UseServices(services =>
{
services.AddMvc();
services.Configure<MvcOptions>(options =>
{
options.Filters.Add(new CustomExceptionFilterAttribute());
});
.....
}
Note that this solution does not cover all scenarios...for example, when an exception is thrown while writing the response by a formatter.

MVVMCross ViewModel construction failure notifications

We've noticed a couple of times in our mobile applications that users have reported the application hanging or seeming to become unresponsive between views / rare crashes when switching between views. We've tracked down these cases to when our view model constructors throw uncaught exceptions.
We want to put a solution in place so that if a view model fails to construct for some reason then we can notify the user and provide some message that will be useful to us when it's logged through support.
I've been taking a look at doing this but haven't found a reliable way to achieve this.
The first thing we tried was at the IMvxViewModelLocator level. We already have a custom implementation of IMvxViewModelLocator so we've modified this. We allow all exceptions to be thrown and then we have an IErrorHandler interface which each platform implements. We then call this to attempt to show a dialog. This has proved to be unreliable and the dialog does not always display. Something along the lines of: (note - here ResolveViewModel will always return true or throw)
public override bool TryLoad(Type viewModelType, IMvxBundle parameterValues, IMvxBundle savedState, out IMvxViewModel viewModel)
{
try
{
return ResolveViewModel(viewModelType, parameterValues, savedState, out viewModel);
}
catch (Exception exception)
{
_errorHandler.HandleViewModelConstructionException(viewModelType, exception);
viewModel = null;
return false;
}
}
What we would ideally like to do is intercept any failure to construct a view model and then re-request an ErrorViewModel. We've tried to do this 2 ways:
1)
We've tried defining a custom IMvxViewDispatcher for each platform and we're trying to intercept failures as below but if an exception in the constructor is thrown we never get back this far:
public class TouchDispatcher : MvxTouchUIThreadDispatcher, IMvxViewDispatcher
{
private readonly IMvxTouchViewPresenter _presenter;
public TouchDispatcher(IMvxTouchViewPresenter presenter)
{
_presenter = presenter;
}
public bool ShowViewModel(MvxViewModelRequest request)
{
Action action = () =>
{
_presenter.Show(request);
};
try
{
bool success = RequestMainThreadAction(action);
return !success ? HandleError() : success;
}
catch (Exception)
{
return HandleError();
}
}
// Other bits
}
2)
We thought we might have more success at the presenter level. We modified our ViewPresenter for each platform and we have overridden void Show(MvxViewModelRequest request). This has not proved to be successful either as exceptions don't propagate back this far.
This leaves me thinking that maybe we are better attempting this at the IMvxViewModelLocator level again.
Has anyone found a way to reliably intercept failures to construct view models and then ideally re-request a different view model / present some dialog to the user?
It seems you've identified that the core of the problem is when: "view model constructors throw uncaught exceptions."
This is going to be slightly problematic as the ViewModel's are generally constructed during View lifecycle overrides like ViewDidLoad, OnCreate or NavigatedTo - which is generally after the Presenter has finished requesting presentation.
As you've already found an easy place to identify when ViewModel construction has failed is in a custom IMvxViewModelLocator - others likeIMvxViewModelLoader are also possible. This is probably the easiest place to catch the error and to trigger the error handling - you can then get hold of the IMvxViewDispatcher (or presenter) there in order to change the display. However, you will still need to make sure your Views can handle null created ViewModels - as the ViewDidLoad, etc calls will still need to complete.

Exception/MessageBox in Calibur.Micro

I start learning Caliburn.Micro and I am little confuse of handling with exception/messange box in view model class.
I found some blogs about, for example:
http://frankmao.com/2010/11/18/handling-messagebox-in-caliburn-micro/
For example some method in view model class which can produce exception.
public void MethodWichCanProduceEx(string arg1, string arg2 )
{
if(arg1==null)
throw new ArgumentNullException("arg1 is null");
if (arg2 == null)
throw new ArgumentNullException("arg2 is null");
try
{
}
catch (Exception exception)
{
throw exception;
//? show message box MessageBox.Shox(exception.Message)
}
}
What is correct handling and showing these exception in view ? It exist any kind of pattern for caliburn.micro?
It possible trace exception as in .NET in text, xml file ?
For example I would like trace exception in xml, text file and in view show only message.box or something message.
Thank for advance, maybe is my question little stupid, sorry I am only learning calibur.micro.
You'll want to always work against abstractions in your view models, in the case of message boxes, you don't want to have to wait for user input when you come to unit test your view models.
The Frank Mao code you linked to uses a delegate to abstract the implementation of the message box from the view model, but I would use an interface here. You can think of a delegate as an interface with a single method, but the advantage of using an interface in this context is that you can have different methods depending on the type of message you wish to show. For example, you could have a ShowMessageError, ShowMessageWarning, ShowMessageInfo etc.
So, define a contract for your message box:
public interface IMessageBox
{
void ShowException(Exception exc);
}
Inject the message box dependency into your view model, e.g. via the constructor
public class MyViewModel
{
private readonly IMessageBox messageBox;
public MyViewModel(IMessageBox messageBox)
{
this.messageBox = messageBox;
}
public void MethodThatCanThrowException()
{
try {}
catch(Exception exc)
{
// log the exception here
...
// show message box
this.messageBox.ShowException(exc);
}
}
}
You can then implement the message box anyway you wish, either using the windows system message box, or nicer still use your own view/viewmodel to display the message, perhaps using the Caliburn.Micro WindowManager.ShowDialog().
An implementation that uses the windows system message box may look like:
public class StandardMessageBox : IMessageBox
{
public void ShowException(Exception exception)
{
MessageBox.Show(exception.ToString(), "Error Occurred");
}
}
In production code, you can register StandardMessageBox against the IMessageBox interface in your IoC container.
In unit test land, you can mock out IMessageBox and have it do nothing, or in the case of methods with a result from the message box, always return a value you wish.
For logging the exception, I would look at a logging framework such as log4net (http://logging.apache.org/log4net/index.html) or NLog (http://nlog-project.org/)

GWT JsonpRequestBuilder Timeout issue

I am getting time out from using JsonpRequestBuilder.
The entry point code goes like this:
// private static final String SERVER_URL = "http://localhost:8094/data/view/";
private static final String SERVER_URL = "http://www.google.com/calendar/feeds/developer-calendar#google.com/public/full?alt=json-in-script&callback=insertAgenda&orderby=starttime&max-results=15&singleevents=true&sortorder=ascending&futureevents=true";
private static final String SERVER_ERROR = "An error occurred while "
+ "attempting to contact the server. Please check your network "
+ "connection and try again.";
/**
* This is the entry point method.
*/
public void onModuleLoad() {
JsonpRequestBuilder requestBuilder = new JsonpRequestBuilder();
// requestBuilder.setTimeout(10000);
requestBuilder.requestObject(SERVER_URL, new Jazz10RequestCallback());
}
class Jazz10RequestCallback implements AsyncCallback<Article> {
#Override
public void onFailure(Throwable caught) {
Window.alert("Failed to send the message: " + caught.getMessage());
}
#Override
public void onSuccess(Article result) {
// TODO Auto-generated method stub
Window.alert(result.toString());
}
The article class is simply:
import com.google.gwt.core.client.JavaScriptObject;
public class Article extends JavaScriptObject {
protected Article() {};
}
The gwt page, however, always hit the onFailure() callback and show this alert:
Failed to send the message. Timeout while calling <url>.
Fail to see anything on the Eclipse plugin console. I tried the url and it works perfectly.
Would appreciate any tip on debugging technique or suggestion
Maybe you should set the callback function explicitly via setCallbackParam, since you have callback=insertAgenda in your url - I presume that informs the server what should be the name of the callback function that wraps the JSON.
Also, it's worth checking Firebug's console (or a similar tool for your browser) - even if GWT doesn't report any exceptions, Firebug still might.
PS: It's useful to use a tool like Firebug to see if the application does in fact receive the response from the server (that would mean that, for example, you do need the setCallbackParam call) or maybe there's something wrong on the server side (for whatever reason).
You have to read the callback request-Parameter (default callback, value something like __gwt_jsonp__.P0.onSuccess) on serversite and have to modify the output to
<callback>(<json>);
In this case:
__gwt_jsonp__.P0.onSuccess(<json>);
Both of these guys are absolutely correct, but here is a concrete example to help you understand exactly what they are referring too.
This is a public JSON api. Take a look at the results:
http://ws.geonames.org/postalCodeLookupJSON?postalcode=M1&country=GB&maxRows=4
This public API supports JSONP through the predefined parameter 'callback'. Basically whatever value you pass into callback, will be used as the function name to wrap around the JSON data you desire. Take a look at the results of these few requests:
http://ws.geonames.org/postalCodeLookupJSON?postalcode=M1&country=GB&maxRows=4&callback=totallyMadeUp
http://ws.geonames.org/postalCodeLookupJSON?postalcode=M1&country=GB&maxRows=4&callback=trollingWithJSONP
It could be happening because of another reason, that the webservice call is returning a JSON object and but the callback is expecting JSONP object (note there is a difference).
So if you are dealing with google maps api, and you are seeing this exception, you need to change it to api provide by maps api, something like
final GeocoderRequest request = GeocoderRequest.create();
request.setAddress(query);
try {
GWT.log("sending GeoCoderRequest");
if (m_geocoder == null) {
m_geocoder = Geocoder.create();
}
m_geocoder.geocode(request, new Geocoder.Callback() {
#Override
public void handle(final JsArray<GeocoderResult> results,
final GeocoderStatus status) {
handleSuccess(results, status);
}
});
} catch (final Exception ex) {
GWT.log("GeoCoder", ex);
}
Or else you could use RequestBuilder as in gwt library.