Sporadically, I receive an error in my WP7 Silverlight application. The error is a random "System.NotSupportedException". This error is thrown occassionally when the following code is executed:
// 1. Build the url
string serviceURL = "http://www.mydomain.com/service.svc/param1/param2";
// 2. Asynchronously execute the query using HttpWebRequest instead of WebClient. There is a UI performance issue with the WebClient currently
WebRequest request = HttpWebRequest.Create(serviceUrl);
request.BeginGetResponse(new AsyncCallback(MyService_Completed), request);
...
private void MyService_Completed(IAsyncResult result)
{
// Do stuff
}
I have verified that the URL I am sending is correct. Please note, that this request is part of my view model, which may have other network requests fired off at the same time. I have no idea why this happens ocassionally. Can anybody point out any potential reasons?
Thank you!
When this happens, make sure you look at the View Detail part of the exception report. It might be that your service is refusing connection or the data passed is invalid. NotSupported is a very general exception that covers many possible situations.
A similar question has been asked previously. If you look at the comments the original poster added to the answer, he claims to have solved the problem by replacing
request.BeginGetResponse(new AsyncCallback(MyService_Completed), request);
with
request.BeginGetResponse( MyService_Completed, request);
Related
I’m working on Camel and focusing on Error Handling.
For irrecoverable errors (those that won’t be fixed by retries), Camel In Action says you should use exchange.getOut().setFault(true) and exchange.getOut().setBody("Error Occurred").
What is the best way to actually handle these errors? Right now I’m thinking there’s two ways:
Using handleFaults(true) on the route or context then handling like any other errors
The original message sender could handle it if Request Reply pattern is used
1 is straight forward to me (except at that point, might as well use Exceptions/Recoverable errors?). 2 is a little trickier – I’m not sure how the original sender will know that the message that they get back is an error (vs. the expected return message).
What I’m thinking could happen is this using Exception to indicate that it’s an error:
In route:
// error occurred
exchange.getOut().setFault(true);
exchange.getOut().setBody(new Exception(“error”));
In sender (jms example using QueueRequestor for Request Reply):
responseMessage = qRequestor.request(msg);
if(responseMessage instanceof ObjectMessage && ((ObjectMessage)responseMessage).getObject() instanceof Exception) {
// AN ERROR OCCURRED IN ROUTE
} else {
// NORMAL PROCESSING OF MESSAGE
}
This just seems like a lot of work on the original sender. Is there a better way of handling this?
Camel can handle the exception well out of box with the help of ErrorHandler, which means your camel route don't need to do much thing about it.
But for the fault message, it's a part of Application level message, Camel ErrorHandler don't want to touch it, so the developer should think about how to handle it.
In my java code, I am processing huge amount of data. So I moved the code as servlet to Cron Job of App Engine. Some days it works fine. After the amount of the data increases, the cron job is not working and shows the following error message.
2012-09-26 04:18:40.627
'ServletName' 'MethodName': Inside SQLExceptionjava.sql.SQLRecoverableException:
Connection is already in use.
I 2012-09-26 04:18:40.741
This request caused a new process to be started for your application, and thus caused
your application code to be loaded for the first time. This request may thus take
longer and use more CPU than a typical request for your application.
W 2012-09-26 04:18:40.741
A problem was encountered with the process that handled this request, causing it to
exit. This is likely to cause a new process to be used for the next request to your
application. If you see this message frequently, you may be throwing exceptions during
the initialization of your application. (Error code 104)
How to handle this problem?
This exception is typical when a single connection is shared between multiple threads. This will in turn happen when your code does not follow the standard JDBC idiom of acquiring and closing the DB resources in the shortest possible scope in the very same try-finally block like so:
public Entity find(Long id) throws SQLException {
Connection connection = null;
// ...
try {
connection = dataSource.getConnection();
// ...
} finally {
// ...
if (connection != null) try { connection.close(); } catch (SQLException ignore) {}
}
return entity;
}
Your comment on the question,
#TejasArjun i used connection pooling with servlet Init() method.
doesn't give me the impression that you're doing it the right way. This suggests that you're obtaining a DB connection in servlet's init() method and reusing the same one across all HTTP requests in all HTTP sessions. This is absolutely not right. A servlet instance is created/initialized only once during webapp's startup and reused throughout the entire remaining of the application's lifetime. This at least confirms the exception you're facing.
Just rewrite your JDBC code according the standard try-finally idiom as demonstrated above and you should be all set.
See also:
Is it safe to use a static java.sql.Connection instance in a multithreaded system?
I realise that similar questions have been asked before however none of the solutions provided worked.
Examining the token returned from the BeginGetResponse method I see that the following exception is thrown there:
'token.AsyncWaitHandle' threw an exception of type 'System.NotSupportedException'
This page tells me that this exception means the Callback parameter is Nothing, however I'm passing the callback - and the debugger breaks into the callback method when I insert a breakpoint. However the request object in the callback is always null. I can view the same exception detail in the result object in the callback method.
I've tried using new AsyncCallback(ProcessResponse) when calling BeginGetResponse
I've tried adding request.AllowReadStreamBuffering = true;
I've tried this in-emulator and on-device, with no luck on either.
public static void GetQuakes(int numDays)
{
HttpWebRequest request = (HttpWebRequest)WebRequest.Create("http://magma.geonet.org.nz/services/quake/geojson/quake?numberDays=" + numDays);
// Examining this token reveals the exception.
var token = request.BeginGetResponse(ProcessResponse, request);
}
static void ProcessResponse(IAsyncResult result)
{
HttpWebRequest request = result.AsyncState as HttpWebRequest;
if (request != null)
{
// do stuff...
}
}
So I'm at a bit of a loss as to where to look next.
'token.AsyncWaitHandle' threw an exception of type
'System.NotSupportedException'
This page tells me that this exception means the Callback parameter is
Nothing
The documentation you are looking at http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.begingetresponse%28v=vs.95%29.aspx is for BeginGetResponse. Silverlight does not use the AsyncWaitHandle, and correctly throws a NotSupportedException. You are seeing the exception System.NotSupportedException is for call to IAsyncResult.AsyncWaitHandle you are making when you inspect token.
The documentation on IAsyncResult.AsyncWaitHandle says explicitly that it is up to the implementation of IAsyncResult whether they create a wait handle http://msdn.microsoft.com/en-us/library/system.iasyncresult.asyncwaithandle(v=vs.95).aspx. Worrying about this is sending you down th wrong path.
I think you need to descibe the actual problem you are seeing. It is great to know what you have investigated, but in this case it does help resolve the problem.
The code should work and in ProcessResponse request should not be null when you test it in the if statement. I just copied the code you have provided into a windows phone application and ran it with no problems.
I have a very strange problem: I'm developing a Silverlight business application with RIA services.
I have some DomainServices on the server-side, and with one of them I'm having the problem, that sometimes calling one of the methods fails (on the SL client, I get "NotFound" exception, and the request doesn't event arrive to the server (I put a breakpoint into the constructor of the domainservice)!
What makes things strange even more:
If the call fails from the SL client, then I start Fiddler2, then the second (or any consecutive) call is working properly! If I close fiddler, it becomes unstable again.
If I rename the method which I would like to call (via refactor), call renamed method on the context at SL client side too, then everytime I make the call it is successful!
Here is my suspicios method:
[Invoke]
public void RegisterTrainingProgramCompletion(bool isCompleted, int result, string sportsManNote)
{
//...
}
If I rename this method to "RegisterTpCompletion", then it works (unbelievable)!
The DomainService is marked with some attributes:
[EnableClientAccess()]
[RequiresAuthentication()]
public class NextTrainingProgramDomainService : DomainService
I managed to somehow log the server-side, and got the following exception from the WCF stack:
There is a problem with the XML that was received from the network. See inner exception for more details. at System.ServiceModel.Channels.HttpInput.DecodeBufferedMessage(ArraySegment`1 buffer, Stream inputStream)
at System.ServiceModel.Channels.HttpInput.ReadBufferedMessage(Stream inputStream)
at System.ServiceModel.Channels.HttpInput.ParseIncomingMessage(Exception& requestException)
at System.ServiceModel.Channels.HttpChannelListener.HttpContextReceived(HttpRequestContext context, Action callback)
at System.ServiceModel.Activation.HostedHttpTransportManager.HttpContextReceived(HostedHttpRequestAsyncResult result)
at System.ServiceModel.Activation.HostedHttpRequestAsyncResult.HandleRequest()
at System.ServiceModel.Activation.HostedHttpRequestAsyncResult.BeginRequest()
at System.ServiceModel.Activation.HostedHttpRequestAsyncResult.OnBeginRequest(Object state)
at System.ServiceModel.AspNetPartialTrustHelpers.PartialTrustInvoke(ContextCallback callback, Object state)
at System.ServiceModel.Activation.HostedHttpRequestAsyncResult.OnBeginRequestWithFlow(Object state)
at System.Runtime.IOThreadScheduler.ScheduledOverlapped.IOCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* nativeOverlapped)
at System.Runtime.Fx.IOCompletionThunk.UnhandledExceptionFrame(UInt32 error, UInt32 bytesRead, NativeOverlapped* nativeOverlapped)
at System.Threading._IOCompletionCallback.PerformIOCompletionCallback(UInt32 errorCode, UInt32 numBytes, NativeOverlapped* pOVERLAP)
So for some unknown reason the clint (SL-app) does not flush properly the request? I'm starting to worry :(((
My callers (SL client) are authenticated with custom forms authentication.
I know you could say, leave it then as it is, but this drives me crazy, I want to know what's the problem, so I do not run into it again.
Thanks!
Bye,
Csabi
I suspect it is URL issue, mostly URL can only be few kbs long. Now I don't know the size but in RIA services, it uses URL to send your filter as querystring.
And names of your method are also big, it is reaching max limit of URL. When it is working even with big name your filter part may be empty but if you add more filters you will face errors.
I'm developing my first windows phone 7 app, and I've hit a snag. basically it's just reading a json string of events and binding that to a list (using the list app starting point)
public void Load()
{
// form the URI
UriBuilder uri = new UriBuilder("http://mysite.com/events.json");
WebClient proxy = new WebClient();
proxy.OpenReadCompleted += new OpenReadCompletedEventHandler(OnReadCompleted);
proxy.OpenReadAsync(uri.Uri);
}
void OnReadCompleted(object sender, OpenReadCompletedEventArgs e)
{
if (e.Error == null)
{
var serializer = new DataContractJsonSerializer(typeof(EventList));
var events = (EventList)serializer.ReadObject(e.Result);
foreach (var ev in events)
{
Items.Add(ev);
}
}
}
public ObservableCollection<EventDetails> Items { get; private set; }
EventDetails is my class that wraps the json string. this class has to be correct because it is an exact copy of the class used by that website internally from which the json is generated...
I get the json string correctly from the webclient call (I read the memorystream and the json is indeed there) but as soon as I attempt to deserialize the string, the application exits and the debugger stops.
I get no error message or any indication that anything happen, it just stops. This happens if I type the deserialize method into the watch window as well...
I have already tried using JSON.net in fact I thought maybe it was a problem with JSON.net so I converted it to use the native deserializer in the .net framework but the error is the same either way.
why would the application just quit? shouldn't it give me SOME kind of error message?
what could I be doing wrong?
many thanks!
Firstly, the fact that you have some string there that looks like JSON does not mean that you have a valid JSON. Try converting a simple one.
If your JSON is valid, it might be that your JSON implementation does not know how to convert a list to EventList. Give it a try with ArrayList instead and let me know.
The application closes because an unhandled exception happens. If check the App.xaml.cs file you will find the code that closes your app. What you need to do is try catch your deserialization process and handle it locally. So most likely you have some JSON the DataContractJsonSerializer does not like. I have been having issue with it deserializing WCF JSON and have had to go other routes.
You may want to check to ensure your JSON is valid, just because your website likes it does not mean it is actually valid, the code on your site may be helping to correct the issue. Drop a copy of your JSON object (the string) in http://jsonlint.com/ to see if it is valid or not. Crokford (the guy who created JSON) wrote this site to validate JSON, so I would rely on it more than your site ;) This little site has really helped me out of some issues over the past year.
I ran into this same kind of problem when trying to migrate some existing WM code to run on WP7. I believe that the WP7 app crashes whenever it loads an assembly (or class?) that references something that's not available in WP7. In my case, I think it was Assembly.Load or something in the System.IO namespace, related to file access via paths.
While your case might be something completely different, the symptoms were exactly the same.
The only thing I can recommend is to go through the JSON library and see if it's referencing base classes that are not allowed in WP7. Note that it doesn't even have to hit the line of code that's causing the issue - it'll crash as soon as it tries to hit the class that contains the bad reference.
If you can step into the JSON library, you can get a better idea of which class is causing the problem, because as soon as the code references it, the whole app will crash and the debugger will stop.