How can I use '$' character in JOLT?

I'm trying to do some data transformation using JOLT for Apache nifi but I'm running into some problem.

The sample input is:

{
  "id": "1234"
}

The sample output is:

{
  "$distinct_id": "1234"
}

My JOLT Specs:

[
  {
    "operation": "shift",
    "spec": {
      "id": "$distinct_id"
    }
  }
]

But i'm getting this error

Error running the Transform.

JOLT Chainr encountered an exception constructing Transform className:com.bazaarvoice.jolt.Shiftr at index:0.

DotNotation (write key) can not contain '*' or '$' : write key: root.$distinct_id

NOTE: the '$' is mandatory as it's my payload for mixpanel

Solution

If your aim is to get exact JSON stated in the sample output, then you can use

[
  {
    "operation": "shift",
    "spec": {
      "id": "\\$distinct_&" // btw, & replicates the current key "id"
    }
  }
]

It has a special meaning that is returning the key's value from the upper node.

This special character $ could be escaped through use of double backslashes.