Access deserialized object from custom deserializer - json

Question

All classes in my model are subclasses of a common base-class Node.
When serializing/deserializing with Jackson, I want references to other objects to be replaced by their ID. The problem is, that the ID is a combination of two values: the ID of the instance itself, and the ID of a source. I do this with a custom serializer and deserializer.
Serializing is no problem. I write JSON with a structure like this:
{"id":1,"source":2,"name":"Some record","reference":3}
But when deserilizing, I need to know the ID of the source and the ID of the referenced node, to be able to look it up in my custom deserializer.
Is it possible, to access the values of the deserialized instance, to get access to the ID of the source when deserializing the reference?
Here is what I tried so far:
public class MyDeserializer extends JsonDeserializer<Node>
{
#Override
public NodeData deserialize(...)
{
Node parent = (Node)parser.getCurrentValue();
Long id = parent.getId();
Long id = parser.getLongValue();
return NodeDataService.INSTANCE.get(source, id);
}
}
But parser.getCurrentValue() always returns a null.
My best solution so far is, to write a cooperation pair of deserializers.
The first one is annotated to the getter of the attribute source and stores
the value as per-call attribute. The second looks like this:
public class MyDeserializer extends JsonDeserializer<Node>
{
#Override
public NodeData deserialize(...)
{
Long source (Long)context.getAttribute("SOURCE");
Long id = parser.getLongValue();
return NodeDataService.INSTANCE.get(source, id);
}
}
This works, but I am asking myself, if there is an easier way to achieve this.
This question looks like it is possible, like I did it in my first attempt - but only while serializing:
Jackson How to retrieve parent bean in a custom Serializer/Deserializer

Answer 1

getCurrentValue() will return null as you've entered into a new JSON object but not yet set the current value. You need to look at the stack of deserialized values in the parser context.
I answered something similar here, which is the deserialization equivalent of the serialization question you linked to: Jackson JSON gives exception on collection of nested class
In summary you can get the stream context:
JsonStreamContext ourContext = p.getParsingContext();
and then repeatedly call getParent() on contexts to walk up the chain, calling getCurrentValue(). The value is set into the stream context as soon as the standard bean deserializer constructs the object.