Missing array order information

[Juan Rada]

Hello folks

I am using jackson xml  to deserialize an array of elements of diferent types like.

<array>

     <type1>...content-1a...<type1/>

     <type2>...content-2...<type2/>

     <type1>...content-1b...<type1/>

<array>

The problem is that when using tree model (JsonParser#readValueAsTree<TreeNode>) in my custom deserializer, this is transformed into json and it becomes

{
    "array" :  {
        "type1": [{content-1a}, {content-1b}]

        "type2": {content-2}

    }
}

As you notice order information is lost.  I am aware (as it said in documentation) that tree modeling has some limitation but I am wondering if there is any suggested workaround. Note that I am using custom serialization register using JacksonXmlModule.addDeserializer and not annotation base approach. 

[Tatu Saloranta]

There is no way to represent such content as JsonNode without losing
some of the ordering information, unfortunately, as duplicate keys are
not allowed.
This is indeed a limitation that cannot be overcome with that model.

One thing that you could do is to instead define a POJO with setters
to match "type1" and "type2": setters will get called
in document order and you can retain ordering using whatever data
structure you want.

Or, alternatively, you could possibly sub-class one of `Map`
implementations (or define a completely custom one), override its
`put()` method which should also be
called for properties, in order. Within that method you could do
something different than call "super.put()".

I hope this helps,

-+ Tatu +-


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