[jsonb-dev] Custom deserialize array property

[Michael Lipp <mnl@xxxxxx>]

Hello,

if this is the wrong place for this topic, I apologize in advance. 
However, I couldn't find or think of anything better place.

I'm trying to port a deserializer from Jackson to Json-B. The Json to 
deserialize looks like this (simplified):

{

    "prop1": "something",

    "prop2": [ "something else", 42, { "attribute": "value" } ]

}

In addition, there is a Java type "class Something { public String 
attribute; }" that should be used for entry 2 in the array in the result 
of the deserialization (actually, the class is more complex).

When deserializing this, I know (from the "rtType" passed to the 
"deserialize" method of my deserializer) the Java types of the elements 
in the array in "prop2". Therefore, I don't want to forward the 
deserialization of the array to the DeserializationContext because it 
does not know about the types used in the array and would use a Map for 
the last element. I want to do it myself.

This is no problem with Jackson, because its equivalent to 
DeserializationContext expects the parser to be positioned on the start 
token of the item to deserialize. I therefore consume the START_ARRAY, 
get the next token, check if it is END_ARRAY, and if it is not, I make 
Jackson deserialize the next (actually current) item with the expected 
Java type.

The Json-B apidoc for DeserializationContext#deserialize states that 
"JsonParser cursor have to be at KEY_NAME before START_OBJECT / 
START_ARRAY, or at START_OBJECT / START_ARRAY to call this method." But 
I cannot leave the cursor at "prop2", because then the 
DeserializationContext deserializes using default types. Of course, I 
could post-process the result created with default mappings and adapt it 
to my expected type. But this requires additional coding and additional 
CPU cycles at run-time.

Is there any solution to this problem that I have missed or is this 
simply a use case that wasn't considered when specifying Json-B?

 -  Michael