I have an exception handling in my application very similar to this solution:
http://www.devcurry.com/2012/06/aspnet-mvc-handling-exceptions-and-404.html
There is a nasty bug in my app where it is possible for the sql to deadlock with an other process. This happens rarely (1-2 requests fail daily because of this), but it still happens.
How can I automatically refresh the page on sql deadlock (and hide the error this way from the end user on get requests)?
Can I do it in the Application_Error function? Or in the overridden OnException in HandleErrorAttribute?
EDIT:
I mocked up some code in the BaseController I created:
protected override void OnException(ExceptionContext filterContext)
{
Exception ex = filterContext.Exception;
SqlException sex = ex as SqlException;
if (sex != null && sex.Number == 1205)
{
Log.Error("Transaction deadlocked with the following exception:");
Log.Exception(sex);
//I need to write the logic that refreshes the page here.
}
else
{
Log.Error("Application error with the following exception:");
Log.Exception(ex);
}
base.OnException(filterContext);
}
I need help on the refresh part.
I would deal with it by overriding the OnException() method of the controller. It would be best if you inherit all your controllers from a custom base one in which the override is done to maintain uniformity and DRYness of the solution.
just add bellow code, before base.OnException(filterContext);
// Stop any other exception handlers from running
filterContext.ExceptionHandled = true;
Related
I am trying to fetch Customer data to parse them into customer object to display on TableView. The following code sometimes works, sometimes not. Whenever it does crash, it shows Customer data is empty in the foreach loop even though I run the same code every time. I do not have clue what could be wrong in this circumstances. I am quite new on this platform. If I am missing anything/ extra information, please let me know.
namespace TableViewExample
{
public partial class MyDataServices : ContentPage
{
private ODataClient mODataClient;
private IEnumerable <IDictionary<string,object>> Customers;
public MyDataServices ()
{
InitializeComponent ();
InitializeDataService ();
GetDataFromOdataService ();
TableView tableView = new TableView{ };
var section = new TableSection ("Customer");
foreach (var customers in Customers) {
//System.Diagnostics.Debug.WriteLine ((string)customers ["ContactName"]);
var name = (string)customers ["ContactName"];
var cell = new TextCell{ Text = name };
section.Add (cell);
}
tableView.Root.Add (section);
Padding = new Thickness (10, 20, 10, 10);
Content = new StackLayout () {
Children = { tableView }
};
}
private void InitializeDataService(){
try {
mODataClient = new ODataClient ("myURL is here");
}
catch {
System.Diagnostics.Debug.WriteLine("ERROR!");
}
}
private void GetDataFromOdataService (){
try {
Customers = mODataClient.For ("Customers").FindEntries ();
}
catch {
System.Diagnostics.Debug.WriteLine("ERROR!");
}
}
}
}
Its hard helping out here, however here are some things to consider:-
It sounds like the dataservice could either be not contactable / offline; too busy or it could even be throwing an exception itself and returning a data response that you are not expecting to receive, that then triggers an exception and crash in your application as your always expecting an exact response without catering for any abnormal responses / events.
If you are contacting an external service over the internet it may just be your internet connection is slow / faulty and not returning the information fast enough as other possibilities.
In your code you are assuming that you always get a response from the server - and that this response will always be of an anticipated structure that your expecting to decode - without factoring in any possibility of abnormal responses returned by the dataservice. I have not used ODataClient personally, so not sure how it behaves in the event of maybe no data received / timeout or in your case the dataservice and how it behaves internally in the response to a bad-request etc.
I am assuming an exception would get thrown, and you do get your debug line executed indicating a failure.
You may want to also adjust this statement so that you write out the exception as well, i.e.:-
private void GetDataFromOdataService ()
{
try
{
Customers = mODataClient.For ("Customers").FindEntries ();
}
catch (Exception ex)
{
System.Diagnostics.Debug.WriteLine("ERROR!" + ex.ToString());
}
}
If there was a bad response, then the line at Customers = ..... would throw the exception as there may be no Customers returned or some other information packaged in the response from the dataservice.
The Customers variable would also be null at this point I am assuming due to this failing.
So when you get back to your code at foreach (var customers in Customers) { it will then throw a null reference exception as Customers is infact null.
As all your current code executes in the constructor without any try and catch block around this, it will also crash your application at this point as well.
Also you are doing all of this work in the constructor. Try seperating this out. I haven't investigated exactly where the constructor gets called in an iOS page life-cycle, however, if it is in the viewDidLoad, then you have something like 10 seconds for everything to complete, otherwise it will exit automatically. I imagine in your case, this isn't applicable however.
Going forward also try putting your layout controls in the constructor, and move your data task to maybe the OnAppearing override instead.
Using async would definitely be advisable as well, but remember you need to inspect the response from your dataservice, as the error could be embedded within the response also and you will need to detect when it is OK to process the data.
I have a BlackBerry App that has a Listener for the Send Button implemented in the CheckIn Screen. Data is sent through a web service. If the data is sent successfully, a confirmation message of "OK" is received. I am trying to switch screens in my BlackBerry App depending on the response received.
FieldChangeListener sendBtnListener = new FieldChangeListener() {
public void fieldChanged(Field field, int context)
{
try {
String alertMsg=sendTextCheckIn();
if(alertMsg.equals("OK"))
{
UiApplication.getUiApplication().invokeLater( new Runnable()
{
public void run ()
{
UiApplication.getUiApplication().pushScreen(new MyScreen());
}
} );
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
However, the above is throwing an App Error 104: IllegalStateException. Can anyone please guide on how to switch screens between a BlackBerry App.
EDIT: I can switch to any other screen but I CAN NOT switch to MyScreen. NOTE: MyScreen is the main (first) screen of the App. The above method sendTextCheckIn() calls another method that is placed inside MyScreen. Has this got anything to do with the error? Please advice.
The 'fieldChanged' event is already running on the UI event thread, so you shouldn't need to do the invokeLater call within it, just call pushScreen directly.
You mention that your problem with IllegalStateException only happens for MyScreen. That makes it sound like something specific with the implementation of MyScreen. Start narrowing down the problem - look at what happens in the constructor of MyScreen, and any events that might get called before the screen is visible. Some of that code is what is causing the problem.
Wrap everything that could possibly raise in exception in try/catch.
Don't do e.printStackTrace() - that won't give you much.
Instead do something like System.err.println ("KABOOM in method abc() - " + e); - seems like more effort, but trust me, that becomes INVALUABLE when debugging issues like this.
Catch Exception, unless you have a VERY good reason to catch a specific a subtype - otherwise you WILL end up with unexpected, and uncaught exceptions, which you will hunt for DAYS.
I'm working on a team-project and I am in the following situation:
I created my own Exception class, and I want all the thrown exceptions of type myException to be handled and automatically redirected to the Error view where I would nicely display the error, which is ok to do. This is what I added in my Web.config:
<customErrors mode="On" defaultRedirect="Error" />
The issue is I want all the rest of the exceptions to be thrown normally, seeing all the information about it, including the stack trace, the source file and the line error, which would be really good for the team-project.
I've tried the [HandleError(ExceptionType=typeof(myException)], but it is no use.
I also tried to override the OnException function of the controller and if the exception is not myException then i would throw it again, but i still get in the Error view.
protected override void OnException(System.Web.Mvc.ExceptionContext filterContext)
{
if (filterContext.Exception.GetType() != typeof(myException)) {
throw filterContext.Exception;
}
base.OnException(filterContext);
}
Any idea which could work?
Thanks.
You may get the result you want by leaving custom errors Off (so that for all the errors you get the stack trace displayed), and redirecting the exceptions you want to the controller/view you need (so that a friendly-looking page will be displayed).
You could define a base controller for all your controllers, and override its OnException method with something like below:
if (filterContext.Exception.GetType() == typeof(YourCustomException))
{
filterContext.ExceptionHandled = true;
filterContext.Result = RedirectToAction("ActionName", "ControllerName", new { customMessage = "You may want to pass a custom error message, or any other parameters here"});
}
else
{
base.OnException(filterContext);
}
I would like to know whether or not it is possible to clear an exception out of the request when trying to hit the Render Phase after the Action Phase has thrown the exception.
If you look at this code snippet from the doRenderService method of DispatchPortlet.class (a Spring provided class):
PortletSession session = request.getPortletSession(false);
if (session != null) {
if (request.getParameter(ACTION_EXCEPTION_RENDER_PARAMETER) != null) {
Exception ex = (Exception)
session.getAttribute(ACTION_EXCEPTION_SESSION_ATTRIBUTE);
if (ex != null) {
logger.debug("Render phase found exception caught during action phase - rethrowing it");
throw ex;
}
}
else {
session.removeAttribute(ACTION_EXCEPTION_SESSION_ATTRIBUTE);
}
}
You can see here that an exception gets put into the parameter map and there doesn't seem to be any way to clear it out.
What I would like to do is originally catch the Exception (what I am successfully doing), display an "Error Page" (what I am successfully doing), then display a button on that Error Page that allows the user to bring up the "Render Phase" page again so that he/she may be able to try their Action, again.
I've tried to create a filter, interceptor, new controller to clear the parameter, but it seems that the ParameterMap is an UnmodifiableCollection.
Any thoughts?
I actually was able to figure this out by doing the following in a render-phase filter:
session.setAttribute(ACTION_EXCEPTION_SESSION_ATTRIBUTE, null)
You can configure your org.springframework.web.portlet.DispatcherPortlet with setForwardActionException(false). This prevents spring from adding the Exception details in render parameters, or session.
I've implemented an ActionFilterAttribute responsible for NHibernate transaction management. Transactions are committed in the OnResultedExecuted override, which occasionally will result in an exception being thrown.
I'm able to successfully intercept these exceptions in the controllers OnException override, however the page still redirects as if the transaction were successful.
What I'd like to be able to do is return the same view action that caused the error with the exceptions message added to the ModelState.
I've tried a number of different things, none of which seem to work.. here's my latest attempt:
[HttpPost]
[Transaction]
[HandleError]
public ActionResult Enroll(EnrollNewEmployeeCommand command)
{
if(command.IsValid())
{
try
{
_commandProcessor.Process(command);
}
catch(Exception exception)
{
ModelState.AddModelError("", exception.Message);
return View(command);
}
return this.RedirectToAction(x => x.Index()); // redirects to index even if an error occurs
}
return View(command);
}
protected override void OnException(ExceptionContext filterContext)
{
//dont interfere if the exception is already handled
if (filterContext.ExceptionHandled)
return;
ModelState.AddModelError("", filterContext.Exception.Message);
filterContext.ExceptionHandled = true;
// want to return original view with updated modelstate
filterContext.Result = new ViewResult
{
ViewName = filterContext.RequestContext.RouteData.Values["action"].ToString(),
ViewData = filterContext.Controller.ViewData
};
}
What I'd like to be able to do is return the same view action that caused the error with the exceptions message added to the ModelState
You can't. OnResultedExecuted happens too late. The view rendering has ended and you can no longer modify what will be sent to the client at this stage.
Your last chance if you want to still be able to modify the returned result to the client is OnResultExecuting. So you could commit your transactions there. Wouldn't be so penalizing I guess.
At the contrary, I would even commit transactions in the OnActionExecuted event, as at this stage all you've got should be a fully initialized view models passed to the view for rendering. That's where your transaction boundaries should end. The process of rendering of the views should be excluded from any transactions and DB stuff. It's just HTML (or something) rendering from a view model, plain and simple.