Jackson handling of remaining fields - json

I wonder if this is possible.
I have a huge json file to parse and modify.
But not all fields are interresting to me : I wan't to map only fields I'm interrested in, modify them then save the whole json with all fields I didn't care left unchanged.
Then suppose I have lot of properties and only one I'm interrested in named "MyProp", I tried something like
public class MyMapper extends HashMap {
private String myProp;
public void setMyProp(String myProp) {
this.myProp = myProp;
}
public String getMyProp() {
return myProp;
}
}
But the property "MyProp" is always null (until I remove "extends HashMap").
Instead all goes in the map.
Wouldn't be useful (or is it already possible ?) to be able to mix concrete fields with maps to work with known fields without loosing unknowns ?
And it would be better to did not extend HashMap but instead having a field to hold all unknown fields like this :
public class MyMapper {
private String myProp;
private Map remaining = new HashMap();
public void setMyProp(String myProp) {
this.myProp = myProp;
}
public String getMyProp() {
return myProp;
}
#JsonRemaining
public Map getRemaining() {
return remaining;
}
}
How would you do in this case ?

Seems like #JsonAnySetter and #JsonAnyGetter annotations might help. All irrelecant proerpties get stuffed into one Map and then the map contents get dumped back to json
See how-to guide here
http://vincentdevillers.blogspot.co.il/2013/08/how-to-map-unknown-json-properties-with.html

Related

Change the json DateTime serialization in WCF 4.0 REST Service

I need to replace the DateTime serialization for JSON in WCF REST Self Hosted service. Right now, I'm using something like the following code to do it, but it's definitely not the way to go since it requires manipulating each class.
[DataContract]
public class Test
{
[IgnoreDataMember]
public DateTime StartDate;
[DataMember(Name = "StartDate")]
public string StartDateStr
{
get { return DateUtil.DateToStr(StartDate); }
set { StartDate = DateTime.Parse(value); }
}
}
where my utility function DateUtil.DateToStr does all the formatting work.
Is there any easy way to do it without having to touch the attributes on my classes which have the DataContract attribute? Ideally, there would be no attributes, but a couple of lines of code in my configuration to replace the serializer with one where I've overridden DateTime serialization.
Everything that I've found looks like I have to replace huge pieces of the pipeline.
This article doesn't appear to apply because in I'm using WebServiceHost not HttpServiceHost, which not part of the 4.5.1 Framework.
JSON.NET Serializer for WCF REST Services
By default WCF uses DataContractJsonSerializer to serialize data into JSON. Unfortunatelly date from this serializer is in very difficult format to parse by human brain.
"DateTime": "\/Date(1535481994306+0200)\/"
To override this behavior we need to write custom IDispatchMessageFormatter. This class will receive all data which should be returned to requester and change it according to our needs.
To make it happen to the operations in the endpoint add custom formatter - ClientJsonDateFormatter:
ServiceHost host=new ServiceHost(typeof(CustomService));
host.AddServiceEndpoint(typeof(ICustomContract), new WebHttpBinding(), Consts.WebHttpAddress);
foreach (var endpoint in host.Description.Endpoints)
{
if (endpoint.Address.Uri.Scheme.StartsWith("http"))
{
foreach (var operation in endpoint.Contract.Operations)
{
operation.OperationBehaviors.Add(new ClientJsonDateFormatter());
}
endpoint.Behaviors.Add(new WebHttpBehavior());
}
}
ClientJsonDateFormatter is simple class which just applies formatter ClientJsonDateFormatter
public class ClientJsonDateFormatter : IOperationBehavior
{
public void AddBindingParameters(OperationDescription operationDescription, BindingParameterCollection bindingParameters) { }
public void ApplyClientBehavior(OperationDescription operationDescription, ClientOperation clientOperation) { }
public void ApplyDispatchBehavior(OperationDescription operationDescription, DispatchOperation dispatchOperation)
{
dispatchOperation.Formatter = new ResponseJsonFormatter(operationDescription);
}
public void Validate(OperationDescription operationDescription) { }
}
In the formatter we took imput and serialize it with the changed Serializer:
public class ResponseJsonFormatter : IDispatchMessageFormatter
{
OperationDescription Operation;
public ResponseJsonFormatter(OperationDescription operation)
{
this.Operation = operation;
}
public void DeserializeRequest(Message message, object[] parameters)
{
}
public Message SerializeReply(MessageVersion messageVersion, object[] parameters, object result)
{
string json=Newtonsoft.Json.JsonConvert.SerializeObject(result);
byte[] bytes = Encoding.UTF8.GetBytes(json);
Message replyMessage = Message.CreateMessage(messageVersion, Operation.Messages[1].Action, new RawDataWriter(bytes));
replyMessage.Properties.Add(WebBodyFormatMessageProperty.Name, new WebBodyFormatMessageProperty(WebContentFormat.Raw));
return replyMessage;
}
}
And to send information to client we need data writer - RawDataWriter. Its implementation is simple:
class RawDataWriter : BodyWriter
{
byte[] data;
public RawDataWriter(byte[] data)
: base(true)
{
this.data = data;
}
protected override void OnWriteBodyContents(XmlDictionaryWriter writer)
{
writer.WriteStartElement("Binary");
writer.WriteBase64(data, 0, data.Length);
writer.WriteEndElement();
}
}
Applying all code will result in returning date in more friendly format:
"DateTime":"2018-08-28T20:56:48.6411976+02:00"
To show it in practice I created example in the github branch DateTimeFormatter.
Please check also this answer as very likely you also will need it.
There is a limitation in JSON to convert DateTime, specially according to your case.
Please see http://msdn.microsoft.com/en-us/library/bb412170(v=vs.110).aspx
and read the section Dates/Times and JSON
To resolve this problem, I simply changed the type of serialization from JSON to XML for all the calls including DateTime.
After long time discussion ,I have find out the solution for it.
Please Use the following Code to Solve serialized date..
[IgnoreDataMember]
public DateTime? PerformanceDate { get; set; }
[DataMember(EmitDefaultValue = false, Name = "PerformanceDate")]
public string UpdateStartDateStr
{
get
{
if (this.PerformanceDate.HasValue)
return this.PerformanceDate.Value.ToUniversalTime().ToString("s", CultureInfo.InvariantCulture);
else
return null;
}
set
{
// should implement this...
}
}

Generic Singleton and share data between pages

To share data (complexe data ) between pages in my windows phone 8 application I want to implement a singleton, but I want it to be generic, is it possible? I suppose that it creates a new instance for each type isn't it?
public sealed class NavigationContextService<T>
{
private static readonly NavigationContextService<T> instance = new NavigationContextService<T>();
private NavigationContextService()
{
}
public static NavigationContextService<T> Instance
{
get
{
return instance;
}
}
public List<T> ShareList { get; set; }
public T ShareData { get; set; }
}
It is creating a new instance for every type, because it is generic - you want it to be like this (if you start with generics, take a look at some tutorials, blogs or MSDN - you will easily find many in the internet).
It is still a singleton. When you use
NavigationContextService<string>.Instance.ShareList.Add("Text");
then you have one Instance for type string. Generics helps a lot when you want to create same methods/classes that differ in type.
On the other hand if you want to create Singleton that will hold different types then you can for example modify your class to be non Generic like this:
public sealed class NavigationContextServiceNonGeneric
{
private static readonly NavigationContextServiceNonGeneric instance = new NavigationContextServiceNonGeneric();
private NavigationContextServiceNonGeneric() { ShareList = new List<object>(); }
public static NavigationContextServiceNonGeneric Instance
{ get { return instance; } }
public List<object> ShareList { get; set; }
public object ShareData { get; set; }
}
As you can see in the code above I haven't defined the 'exact' type of shared data - it is object type. Then you can easily hold most of data with it:
NavigationContextServiceNonGeneric.Instance.ShareList.Add("Text");
NavigationContextServiceNonGeneric.Instance.ShareList.Add(3);
NavigationContextServiceNonGeneric.Instance.ShareList.Add(3.0f);
It is singleton, which can hold different types of shared data. BUT it has also disavantages - the main is that you have to remember what type of data you hold and in what order. In my opinion Generic version is better because of that fact.
Everything depends on the purpose of your code. There may be easier and better ways that those two approaches.
As for the Page Navigation, you can for example try to use a method from this article - you extend Navigation service to pass the object:
public static class Extensions
{
private static object Data;
public static void Navigate(this NavigationService navigationService, Uri source, object data)
{
Data = data;
navigationService.Navigate(source);
}
public static object GetNavigationData(this NavigationService service) { return Data; }
}
Then you use it:
NavigationService.Navigate(yourUri, DataToPass);
After Navigation you can get your data:
string myTextData = NavigationService.GetNavigationData() as string;
This method has to disadvantages: it is not type-safe and your data won't be preserved in Tombstone mode.
As for the second disadvantage you can easily use PhoneApplicationService.State Property for the purpose of Page Navigation - it is a dictionary (which is preserved while tombstoning):
PhoneApplicationService.Current.State.Add("data", yourData);
Then when you want to get your data:
yourDataType yourData = PhoneApplicationService.Current.State["data"] as yourDataType;
There are also more ways in which you can pass the data.

Emit odata.type field with DataContractJsonSerializer?

Is there a way to make DataContractJsonSerializer emit the "odata.type" field required when posting an OData entity into a collection that supports multiple entity types (hierarchy per table)?
If I construct DataContractJsonSerializer with a settings object with EmitTypeInformation set to Always, it emits a "__type" field in the output, but that's not the field name needed for OData and the format of the value is wrong as well.
Is there any way to hook into the DataContractJsonSerializer pipeline to inject the desired "odata.type" field into the serialization output?
It would be such a hack to have to parse the serialization output in order to inject the field. How does WCF Data Services do it? Not using DataContractJsonSerializer is my guess.
Have you considered using Json.Net? Json.Net is much more extensible and the scenario that you have can be done using a custom resolver. sample code
class Program
{
static void Main(string[] args)
{
Console.WriteLine(
JsonConvert.SerializeObject(new Customer { Name = "Raghu" }, new JsonSerializerSettings
{
ContractResolver = new CustomContractResolver()
}));
}
}
public class CustomContractResolver : DefaultContractResolver
{
protected override JsonObjectContract CreateObjectContract(Type objectType)
{
JsonObjectContract objectContract = base.CreateObjectContract(objectType);
objectContract.Properties.Add(new JsonProperty
{
PropertyName = "odata.type",
PropertyType = typeof(string),
ValueProvider = new StaticValueProvider(objectType.FullName),
Readable = true
});
return objectContract;
}
private class StaticValueProvider : IValueProvider
{
private readonly object _value;
public StaticValueProvider(object value)
{
_value = value;
}
public object GetValue(object target)
{
return _value;
}
public void SetValue(object target, object value)
{
throw new NotSupportedException();
}
}
}
public class Customer
{
public string Name { get; set; }
}
I can't answer your first two questions, but for the third question, I found on the OData Team blog a link to the OData WCF Data Services V4 library open source code. Downloading that code, you will see that they perform all serialization and deserialization manually. They have 68 files in their two Json folders! And looking through the code they have comments such as:
// This is a work around, needTypeOnWire always = true for client side:
// ClientEdmModel's reflection can't know a property is open type even if it is, so here
// make client side always write 'odata.type' for enum.
So that to me kind of implies there is no easy, clean, simple, elegant way to do it.
I tried using a JavaScriptConverter, a dynamic type, and other stuff, but most of them ended up resorting to using Reflection which just made for a much more complicated solution versus just using a string manipulation approach.

Custom types in Navigation parameters in v3

In v3 if I wanted to pass two objects to another viewmodel:
public class Dog
{
}
public class Cat
{
}
var dog = new Dog();
var cat = new Cat();
ShowViewModel<SomeViewModel>(new {Dog = dog, Cat = cat });
public class SomeViewModel
{
Init(Dog dog, Cat cat)
{
}
}
As far as I can tell that won't work because the types aren't recognized and can't be stuck in a dictionary. If I wanted to have these serialized as json, passed to the view model, and deserialized as Init parameters, would I implement IExtraParser? And if that is correct, how do I go about adding the implementations to the ExtraParsers dictionary?
update:
This seems to do it:
var foo = Mvx.Resolve<IMvxFillableStringToTypeParser>();
foo.ExtraParsers.Add(new MyParser());
The default navigation mechanism in MvvmCross is deliberately lightweight.
It is really there to allow you to pass just one simple, serializable object - e.g.
public class DogNav
{
public int Id {get;set;}
public string Caption {get;set;}
}
// received in:
public class DogViewModel : MvxViewModel
{
public void Init(DogNav dogNav)
{
}
}
With this setup, if a navigation is triggered like:
// navigation
ShowViewModel<DogViewModel>(new DogNav() { Id=12, Caption="Good boy" });
then the underlying system will transport the values from that DogNav object - possibly using Uris, Intents or other serialization techniques - to the new DogViewModel and will then ensure Init is called with the correct values.
Because of the serialization, it's important:
not to pass big objects (Uris on WindowsPhone can break above a few hundred characters)
not to expect the same object instance to arrive - i.e. if you are using database-backed or stateful objects, then it's best to pass some kind of lookup key rather than the objects themselves.
not to expect that only one ViewModel will receive the message - on some operating systems, it may be that the user goes back and forth many, many times between apps causing many Views and ViewModels to be created.
not to expect that a ViewModel that receives the message is in the same process and memory space as the ViewModel that sent the request - the same may actually be received days later after a tombstoning event.
If you do want to pass multiple objects via navigation, then I think you can do this using code like:
public class CatNav
{
public int CatId {get;set;}
public string CatCaption {get;set;}
}
public class DogNav
{
public int DogId {get;set;}
public string DogCaption {get;set;}
}
// received in:
public class CatAndDogViewModel : MvxViewModel
{
public void Init(DogNav dogNav)
{
}
public void Init(CatNav catNav)
{
}
}
In this case you could navigate using:
var catNav = new CatNav() { CatId =12, CatCaption="Meow" };
var dogNav = new DogNav() { DogId =12, DogCaption="Woof" };
var bundle = new MvxBundle();
bundle.Write(catNav);
bundle.Write(dogNav);
ShowViewModel<CatAndDogViewModel>(bundle);
I think this would work...
However... please be aware that the serialization is very simple - so if CatNav and DogNav were to share a property name, then this would lead to problems - you'd end up with some Cags and Dots
Because of the Cag and Dot problem I don't recommend this approach...
If you do need more complex transitions in your apps, then one route is to:
UPDATE - see Passing complex navigation parameters with MvvmCross ShowViewModel
1. Add the Json Plugin (or any Json serializer) and change your Setup.cs code to create a MvxJsonNavigationSerializer - overriding CreateNavigationSerializer
protected override IMvxNavigationSerializer CreateNavigationSerializer()
{
return new MvxJsonNavigationSerializer();
}
Use a composite object in navigation like:
public class DogAndCatNav
{
public DogNav DogNav {get;set;}
public CatNav CatNav {get;set;}
}
This would be received by:
public void Init(DogAndCatNav dogAndCatNav)
{
}
But note that this technique does need a more powerful serialization engine - such as Json.
Overall... even after writing all this... I'd recommend you pass as little data as possible in your navigations!

GXT 3.0 JsonReader with multiple root objects

I'm starting out with GXT and am a bit confused on how to use the JsonReader to parse a valid json string with multiple root objects. I have a set of selection boxes to build the sql statement to display records in a grid. I'm getting the values for the selections from the database as well. What I'm attempting to do is a single request to my php database functions to build the json with all the values for the selection boxes in one string. My first thought was the JsonReader.
Here's an example of the json I'm working with:
"categories":[{"id":"1","value":"categoryValue1"},{"id":"2","value":"categoryValue2"}], "frequencies":[{"id":"1","value":"frequencyValue1"},{"id":"2","value":"frequencyValue2"}]
Building off the cityList example in the api, this is what I've got so far.
JsonRootObject interface:
public interface JsonRootObject {
List<SelectionProperties> getCategories();
List<SelectionProperties> getFrequencies();
}
JsonRootObjectAutoBeanFactory:
public interface JsonRootObjectAutoBeanFactory extends AutoBeanFactory {
AutoBean<JsonRootObject> jsonRootObject();
}
I created a SelectionProperties interface as all are single int/string value pairs:
public interface SelectionProperties {
String getId();
String getValue();
}
Now, according to the api:
// To convert from JSON data, extend a JsonReader and override
// createReturnData to return the desired type.
So I created a reader for both categories and frequencies;
CategoryReader:
public class CategoryReader
extends
JsonReader<ListLoadResult<SelectionProperties>, JsonRootObject> {
public CategoriesReader(AutoBeanFactory factory, Class<JsonRootObject> rootBeanType) {
super(factory, rootBeanType);
}
protected ListLoadResult<SelectionProperties> createReturnData(Object loadConfig, JsonRootObject incomingData) {
return new ListLoadResultBean<SelectionProperties>(incomingData.getCategories());
}
}
FrequencyReader:
public class FrequencyReader extends
JsonReader<ListLoadResult<SelectionProperties>, net.apoplectic.testapps.client.JsonRootObject> {
public FrequencyReader(AutoBeanFactory factory, Class<JsonRootObject> rootBeanType) {
super(factory, rootBeanType);
}
protected ListLoadResult<SelectionProperties> createReturnData(Object loadConfig, JsonRootObject incomingData) {
return new ListLoadResultBean<SelectionProperties>(incomingData.getFrequencies());
}
}
This doesn't feel quite right. I'm creating multiple instances of basically the same code and parsing the actual json string twice (at this point. I may have more options for the grid once I dig in). My question is am I missing something or is there a more efficient way to parse the response string? From my onSuccessfulResponse:
JsonRootObjectAutoBeanFactory factory = GWT.create(JsonRootObjectAutoBeanFactory.class);
CategoryReader catReader = new CategoriesReader(factory, JsonRootObject.class);
FrequencyReader freqReader = new FrequenciesReader(factory, JsonRootObject.class);
categories = catReader.read(null, response);
frequencies = freqReader.read(null, response);
List<SelectionProperties> categoriesList = categories.getData();
List<SelectionProperties> frequenciesList = frequencies.getData();
ListBox cateBox = new ListBox(false);
ListBox freqBox = new ListBox(false);
for (SelectionProperties category : categoriesList )
{
cateBox.addItem(category.getValue(), category.getId());
}
for (SelectionProperties frequency : frequenciesList)
{
freqBox.addItem(frequency.getValue(), frequency.getId());
}
The above does work, both the ListBoxes are populated correctly. I just wonder if this is the correct approach. Thanks in advance!