Facing issue with JOLT transformation with nested array - jolt

Question

I have a JSON input :
{
"id": "Root_ID",
"Item": [
{
"id": "ID_1",
"characteristic": [
{
"name": "char1",
"value": "PRE1"
},
{
"name": "char2",
"value": "2050-01-01"
}
]
},
{
"id": "ID_2",
"characteristic": [
{
"name": "char1",
"value": "PRE2"
},
{
"name": "char2",
"value": "2050-01-02"
}
]
}
]
}
which needs to be converted by using a Jolt transformation spec to the following output :
{
"id": "Root_ID",
"Item": [
{
"id": "ID_1",
"char1": "PRE1",
"char2": "2050-01-01"
},
{
"id": "ID_2",
"char1": "PRE2",
"char2": "2050-01-02"
}
]
}
Currently, I'm using this spec :
[
{
"operation": "shift",
"spec": {
"id": "id",
"Item": {
"*": {
"characteristic": {
"*": {
"name": {
"char1": {
"#(2,value)": "item[#3].char1"
},
"char2": {
"#(2,value)": "item[#3].char2"
}
}
}
}
}
}
}
}
]
which does not produce the desired result.
Can you please help me prepare a correct spec to handle this issue ?
Edit : What if I'd like to get the following JSON result ?
{
"id": "Root_ID",
"Item": [
{
"id": "ID_1",
"char1": "PRE1"
},
{
"id": "ID_2",
"char1": "PRE2",
"char2": "2050-01-02"
}
]
}

Answer 1

You can use the following shift transformation spec in which #value and #name are matched reciprocally such as
[
{
"operation": "shift",
"spec": {
"id": "&",
"Item": {
"*": {
"id": "&2[&1].&",// you can reduce two levels based on the inner identifier 4,3 -> 2,1
"char*": {
"*": {
"#value": "&4[&3].#name" // &4 copies the literal "Item" after going four levels up the tree, [&3] generates array-wise result(array of objects) after going three levels up the tree to reach the level of the indexes of the "Item" array
}
}
}
}
}
}
]
Edit : You can alternatively use the following spec for the case in which you need to return char2 within the all objects but the first :
[
{
"operation": "shift",
"spec": {
"id": "&",
"Item": {
"0": {// stands for the first index
"id": "&2[&1].&",
"char*": {
"*": {
"name": {
"char1": {
"#2,value": "&6[&5].#3,name"
}
}
}
}
},
"*": {
"id": "&2[&1].&",
"char*": {
"*": {
"#value": "&4[&3].#name"
}
}
}
}
}
}
]