JOLT subtree validation based on one of the property values - jolt

Question

I am a jolt newbie.
I have the following question, I have a JSON document structure of which may vary based on the type property. See my example below.
{
"recipientId": "xxx",
"messages": [
{
"type": "text",
"text": "hi there!"
},
{
"type": "image",
"url": "http://example.com/image.jpg",
"preview": "http://example.com/thumbnail.jpg"
}
]
}
After transformation I would like to receive the following output:
{
"messages" : [ {
"text" : "hi there!",
"type" : "text"
}, {
"type" : "image",
"url" : "http://example.com/image.jpg",
"preview": "http://example.com/thumbnail.jpg"
} ],
"to" : "xxx"
}
Here is the spec that I came up with:
[
{
"operation": "shift",
"spec": {
"recipientId": "to",
"messages": {
"*": {
"type": "messages[&1].type",
"text": "messages[&1].text",
"url": "messages[&1].url",
"preview": "messages[&1].previewImageUrl"
}
}
}
}
]
The problem with this approach is that if I have "type": "text" and if I also throw "preview" property with the value, it will not make sense as the type text should not have "preview" property set.
So, I would like jolt to either ignore some properties based on the value of "type" property or avoid transforming such payloads.
Is there a way to do such "validations" in JOLT? The other option that I see would be validating it with Jackson type hierarchy.

Answer 1

What you can do is match down to the value of "type", and then jump back up the tree some, and process the message as a "text" type or an "image" type.
Input
{
"recipientId": "xxx",
"messages": [
{
"type": "text",
"text": "hi there!",
"preview": "SHOULD NOT PASS THRU"
},
{
"type": "image",
"url": "http://example.com/image.jpg",
"preview": "http://example.com/thumbnail.jpg"
}
]
}
Spec
[
{
"operation": "shift",
"spec": {
"recipientId": "to",
"messages": {
"*": { // the array index of the messages array, referenced below
// as [&2] or [&4] depending how far down they have gone
"type": {
// always pass the value of type thru
"#": "messages[&2].type",
"text": {
// if the value of type was "text", then
// go back up the tree 3 levels (0,1,2)
// and process the whole message as a "text" type
"#2": {
"text": "messages[&4].text"
}
},
"image": {
"#2": {
// if the value of type was "image", then
// go back up the tree 3 levels (0,1,2)
// and process the whole message as a "image" type
"url": "messages[&4].url",
"preview": "messages[&4].previewImageUrl"
}
}
}
}
}
}
}
]