Override Json Serialization RavenDB

Question

I am experimenting with RavenDB. We have a significant number of entity objects which are decorated with attributes as per the following (simple) example:

[Entity(UniqueID = "37AA8322-597D-48E8-BB66-7B2796103D95")]
public class SampleEntity : Entity
{
    protected SampleEntity()
    {

    }

    public static SampleEntity Create()
    {
        return EntityFactory.Create<SampleEntity>();
    }

    [Property]
    public virtual int Integer { get; set; }
}

The type emitted by EntityFactory is actually a sub-class of SampleEntity which overrides the setter/getter automatically implementing INotifyPropertyChanged and keeping track of when each property was last modified (among other things).

Using Json.NET I threw together a Json serializer for Entity's which, for an instance of SampleEntity with 'Integer' set to 8 would spit out something similar to the following:

{
  "TypeID": "\"37aa8322-597d-48e8-bb66-7b2796103d95\"",
  "UniqueID": "\"e1f03e21-260f-4bde-8bfb-ec7a47b2e379\"",
  "Integer": {
    "Last Set": "2014-09-30T14:06:08.9146417Z",
    "Value": "8"
  }
}

Notice how the 'Integer' property gets expanded to include both 'Value' and 'Last Set'. If I ask RavenDB to store a SampleEntity, I (as expected) don't get 'Last Set' inline with 'Value' (In the base class there is a dictionary mapping property names to information about the property, one field being when the property was last set).

Ideally, I would like to store the output of the Json-Entity serializer I wrote in RavenDB (with the UniqueID which gets automatically generated for each Entity as the document ID). When I retrieve a document, it would be raw json and I would be responsible for using that to hydrate the appropriate entity object. I have searched extensively and could not find an easy way to accomplish this, which historically has meant I'm trying to do something stupid.

I am new to both RavenDB (document databases in general) and Json, so perhaps I'm trying to jam a square peg into a round hole here and there is a more elegant way to handle the situation.

Does anybody know a way to store raw json in RavenDB? Or have any comments/suggestions on another way I can accomplish what I have described?

Answer 1

One option would be to use a converter to customize the RavenJObject that gets written to the database, and to customize the way that your desired return object gets filled.

Heres some code:

public class SampleEntityConverter : IDocumentConversionListener
{
    public void EntityToDocument(string key, object entity, RavenJObject document, RavenJObject metadata)
    {
        var obj = entity as SampleEntity;
        if (obj == null)
        {
            return;
        }

        var integer = new RavenJObject();
        integer["Last Set"] = obj.HoweverYouGetTheLastSetDateTime;
        integer["Value"] = obj.Integer;
        document["Integer"] = integer;
    }

    public void DocumentToEntity(string key, object entity, RavenJObject document, RavenJObject metadata)
    {
        var obj = entity as SampleEntity;
        if (obj == null)
        {
            return;
        }

        var integer = document["Integer"] as RavenJObject;       
        if (integer != null && integer.ContainsKey("Value"))
        {
            obj.Integer = integer["Value"];
        }
    }
}

Then register it on your DocumentStore instance:

documentStore.RegisterListener(new SampleEntityConverter());

Answer 2

You can register the same converter using the internalized copy of JSON.Net that RavenDB uses. In the Conventions, look at the CustomizeSerialize method