JOLT get only one value from an array inside an array - json

Question

I've been trying to figure out how to get the first value out of an array in my events array in this JSON.
I think I must do something with Cardinality but I can't quite figure it out so any help would be appreciated.
This is what my JSON looks like
{
"rootid": "19718",
"clloadm": "2021-06-01T22:40:02",
"clload": "2021-06-01T21:21:39",
"date": "2021-05-25T21:52:30",
"events": [
{
"done": {
"id": "e0",
"value": "2021-05-29T08:08:19"
},
"id": "e0_event",
"started": {
"id": "e0",
"value": "2021-05-29T08:08:19"
},
"status": "complete"
},
{
"done": {
"id": "e1",
"value": "2021-05-27T02:20:25"
},
"id": "e1_event",
"started": {
"id": "e1",
"value": "2021-05-27T02:20:25"
},
"status": "complete"
},
{
"done": {
"id": "e2",
"value": "2021-05-29T08:08:19"
},
"id": "e2_event",
"started": {
"id": "e2",
"value": "2021-05-29T08:08:19"
},
"status": "complete"
},
{
"done": {
"id": "e3",
"value": "2021-05-29T08:08:19"
},
"id": "e3_event",
"started": {
"id": "e3",
"value": "2021-05-29T08:08:19"
},
"status": "complete"
},
{
"done": {
"id": "e4",
"value": "2021-05-29T08:08:19"
},
"id": "e4_event",
"started": {
"id": "e4",
"value": "2021-05-29T08:08:19"
},
"status": "complete"
}
],
"ids": [
{
"id": "id",
"source": "source",
"value": "value"
}
]
}
My Jolt Spec
[
{
"operation": "shift",
"spec": {
"*": "&",
"events": {
"*": {
"*": {
"#id": {
"e0": { "#(2,value)": "&" },
"e4": { "#(2,value)": "&" }
}
}
}
},
"ids": {
"*": {
"#value": "#id"
}
}
}
}
]
The result I get:
{
"rootid" : "19718",
"clloadm" : "2021-06-01T22:40:02",
"clload" : "2021-06-01T21:21:39",
"date" : "2021-05-25T21:52:30",
"e0" : [ "2021-05-29T08:08:19", "2021-05-29T08:08:19" ],
"e4" : [ "2021-05-29T08:08:19", "2021-05-29T08:08:19" ],
"id" : "value",
"new_id" : "value"
}
I would like the result to be more like this where only the first value is selected:
{
"rootid" : "19718",
"clloadm" : "2021-06-01T22:40:02",
"clload" : "2021-06-01T21:21:39",
"date" : "2021-05-25T21:52:30",
"e0" : "2021-05-29T08:08:19",
"e4" : "2021-05-29T08:08:19",
"id" : "value",
"new_id" : "value"
}
Edit:
I've tried adding the cardinality into my spec, but I can't seem to get the result I want.
[
{
"operation": "shift",
"spec": {
"*": "&",
"events": {
"*": {
"*": {
"#id": {
"e0": { "#(2,value)": "&" },
"e4": {
"operation": "cardinality",
"spec": {
"e4": "ONE"
}
}
}
}
}
},
"ids": {
"*": {
"#value": "#id"
}
}
}
}
]

Answer 1

Yes, you just can add a cardinality transformation such as
{
"operation": "cardinality",
"spec": {
"*": "ONE"
}
}
or optionally use e* wildcard just to restrict the result for the arrays with keys starting with the letter e such as
{
"operation": "cardinality",
"spec": {
"e*": "ONE"
}
}
Edit : just need to add to the current spec. So, you can use the following :
[
{
"operation": "shift",
"spec": {
"*": "&",
"events": {
"*": {
"*": {
"#id": {
"e0": {
"#(2,value)": "&"
},
"e4": {
"#(2,value)": "&"
}
}
}
}
},
"ids": {
"*": {
"#value": "#id"
}
}
}
},
{
"operation": "cardinality",
"spec": {
"e*": "ONE"
}
}
]