Breeze Web API with Cordova Phone App Saving Changes

Question

I created an ASP.NET MVC 4 Web API project and installed Breeze including Client samples via NuGet and the ToDo application works really well. I also have the app running via Cordova on an Android tablet calling out to the WebAPI and this works great too except when saving entities. I have made the appropriate changes to Global.asax ("Access-Control-Allow-Origin", "*") to support cross domain operations.

Data is actually being saved to the database when the Android Client calls it's saveChanges() but it's fail promise is always firing on the client.

On the Web API server I've noticed that when making Breeze calls via a browser I get the following output trace and successful saves:

iisexpress.exe Information: 0 : Operation=ODataActionFilter.ActionExecuting
iisexpress.exe Information: 0 : Message='Action returned 'Breeze.WebApi.SaveResult'', Operation=ReflectedHttpActionDescriptor.ExecuteAsync
iisexpress.exe Information: 0 : Message='Will use same 'JsonMediaTypeFormatter' formatter', Operation=JsonMediaTypeFormatter.GetPerRequestFormatterInstance
iisexpress.exe Information: 0 : Message='Selected formatter='JsonMediaTypeFormatter', content-type='application/json; charset=utf-8'', Operation=DefaultContentNegotiator.Negotiate
iisexpress.exe Information: 0 : Operation=ApiControllerActionInvoker.InvokeActionAsync, Status=200 (OK)
iisexpress.exe Information: 0 : Operation=ODataActionFilter.ActionExecuted, Status=200 (OK)
iisexpress.exe Information: 0 : Operation=BreezeSampleController.ExecuteAsync, Status=200 (OK)
**iisexpress.exe Information: 0 : Response, Status=200 (OK), Method=POST, Url=http://localhost:59912/api/BreezeSample/SaveChanges, Message='Content-type='application/json; charset=utf-8', content-length=unknown'**
iisexpress.exe Information: 0 : Operation=JsonMediaTypeFormatter.WriteToStreamAsync
iisexpress.exe Information: 0 : Operation=BreezeSampleController.Dispose

But when called from the Android App I get data written but this trace with an error:

iisexpress.exe Information: 0 : Message='Action returned 'Breeze.WebApi.SaveResult'', Operation=ReflectedHttpActionDescriptor.ExecuteAsync
iisexpress.exe Information: 0 : Message='Will use same 'XmlMediaTypeFormatter' formatter', Operation=XmlMediaTypeFormatter.GetPerRequestFormatterInstance
iisexpress.exe Information: 0 : Message='Selected formatter='XmlMediaTypeFormatter', content-type='application/xml; charset=utf-8'', Operation=DefaultContentNegotiator.Negotiate
iisexpress.exe Information: 0 : Operation=ApiControllerActionInvoker.InvokeActionAsync, Status=200 (OK)
iisexpress.exe Information: 0 : Operation=ODataActionFilter.ActionExecuted, Status=200 (OK)
iisexpress.exe Information: 0 : Operation=BreezeSampleController.ExecuteAsync, Status=200 (OK)
**iisexpress.exe Information: 0 : Response, Status=200 (OK), Method=POST, Url=http://192.168.1.9:59912/api/BreezeSample/SaveChanges, Message='Content-type='application/xml; charset=utf-8', content-length=unknown'**
iisexpress.exe Error: 0 : Operation=XmlMediaTypeFormatter.WriteToStreamAsync, Exception=System.Runtime.Serialization.SerializationException: Type 'SMHMobileAPI.Models.BreezeSampleTodoItem' with data contract name 'BreezeSampleTodoItem:http://schemas.datacontract.org/2004/07/SMHMobileAPI.Models' is not expected. Consider using a DataContractResolver or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to DataContractSerializer.
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiType(XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle objectTypeHandle, Type objectType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at WriteArrayOfanyTypeToXml(XmlWriterDelegator , Object , XmlObjectSerializerWriteContext , CollectionDataContract )
   at System.Runtime.Serialization.CollectionDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at WriteSaveResultToXml(XmlWriterDelegator , Object , XmlObjectSerializerWriteContext , ClassDataContract )
   at System.Runtime.Serialization.ClassDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.WriteDataContractValue(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithoutXsiType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.DataContractSerializer.WriteObject(XmlWriter writer, Object graph)
   at System.Net.Http.Formatting.XmlMediaTypeFormatter.<>c__DisplayClass7.<WriteToStreamAsync>b__6()
   at System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action, CancellationToken token)

Apart from some serialisation error I also notice the post header "application/xml". I'm not sure if this is relevant but I sure would like some help to try and find a solution if anyone can help please.

Thanks Mark

Answer 1

I'm pretty sure "application/xml" is relevant.

After save, the Breeze Web API controller returns the update/added entities to you. The "Accept" header you mention would cause the Web API to try to format those entities with the XML formatter which almost always fails.

I don't think Breeze natively sets an Accept header on the POST (I'm not sure if it sets the Accept header on the GET either).

A look at the jQuery AJAX generated request in IE10 shows that the Accept header for a GET is "application/json, text/javascript, */*; q=0.01". For a POST the Accept and Content-type headers are "*\*" and "application/json" respectively.

What are the Accept headers in your Android traffic? You didn't specify which header was set to "application/xml" ... but since that is always "wrong" I don't suppose it matters :)

You can customize the Breeze AJAX adapter or replace it entirely as described here. You might try:

// get the current default Breeze ajax adapter
 var ajaxAdapter = breeze.core.config.getAdapterInstance("ajax");
 // set fixed headers
 ajaxAdapter.defaultSettings = {
       headers: { 
           "Accept": "application/json, text/javascript, */*; q=0.01"
       },
};

That seemed to do the trick in my tests on both IE10 and Chrome.

I will also recommend that the Breeze Web API JsonFormatterAttribute remove the XML formatter give tnat we know that one doesn't work for Breeze traffic.

Hope this works.