Remove null from array using jolt

I have some issue removing the null values from an array using jolt as describe bellow:

Input

{
  "userId": "1",
  "age": "20",
  "firstName": "firstname1",
  "lastname": "lastname1",
  "zipCode": "zipcode1",
  "street": "street1",
  "city": "city1",
  "country": "country",
  "gender": "gender1",
  "grade": "grade1",
  "birthday": "birthday1"
}

Jolt spec

[
  {
    "operation": "shift",
    "spec": {
      "userId": "ID",
      "age": "age",
      "firstName": "firstName",
      "lastname": "lastname",
      "gender": "gender",
      "grade": "grade",
      "birthday": "birthday",
      "street|city|zipCode|country": {
        "$": "address[#2].code",
        "@": "address[#2].value"
      }
    }
  }
]

Output

{
  "ID": "1",
  "age": "20",
  "firstName": "firstname1",
  "lastname": "lastname1",
  "gender": "gender1",
  "grade": "grade1",
  "birthday": "birthday1",
  "address": [ null, null, null, null, null, null, null,
    {
      "code": "street",
      "value": "street1"
    },
    {
      "code": "city",
      "value": "city1"
    },
    {
      "code": "zipCode",
      "value": "zipcode1"
    },
    {
      "code": "country",
      "value": "country"
    }
  ]
}

I had some solutions suggested by @Barbaros thanks to him as describe in the link Remove null values from JSON output using Jolt

but still struggling with it, Any help would be appreciate.

Solution

You can prefix key-value pairs with a literal such as adr_ in the first step, and then use within the last step to distinguish the rest of the attributes those will be sybolized by "*":"&" pair such as

[
  {
    "operation": "shift",
    "spec": {
      "userId": "ID",
      "*": "&",
      "street|city|zipCode|country": {
        "$": "adr_&.code",
        "@": "adr_&.value"
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": "&",
      "adr_*": "address[]"
    }
  }
]

where only "userId": "ID" written individually so as to rename it as desired.