Transform complex Json array using Jolt

Question

When Calling an external API I am receiving a complex json structure, the same I need to transform into a simple json as per our need. I found jolt has the capability to transform a json but not able to come up with the jolt spec.

My input Json array --

{
  "attribute": [
    "teamalloc",
    "prodAlloc"
  ],
  "item": {
    "id": "abcde",
    "name": "Champak Kumar",
    "allocDetails": {
      "updatedAt": "2020-08-10T14:26:48-07:00",
      "token": 1134,
      "items": [
        {
          "allocation": 0.2,
          "team": {
            "id": 90,
            "name": "Some Team Name 1",
            "createdAt": "2010-01-19T10:52:52-07:00"
          }
        },
        {
          "allocation": 0.9,
          "team": {
            "id": 80,
            "name": "Some Team Name 2",
            "createdAt": "2010-01-19T10:52:52-07:00",
            "product": {
              "id": 20,
              "name": "Some Product Name 1",
              "otherDetails": {
                "key": "Id",
                "value": "GEC"
              }
            }
          }
        },
        {
          "allocation": 0.1,
          "team": {
            "id": 10,
            "name": "Some Team Name 3",
            "createdAt": "2010-01-19T10:52:52-07:00",
            "product": {
              "id": 22,
              "name": "Some Product Name 2",
              "otherDetails": {
                "key": "Id1",
                "value": "GEC1"
              }
            }
          }
        }
      ]
    }
  }
}

My output Json structure should look like --

{
  "name": "Champak Kumar",
  "allocDetails": [
    {
      "allocation": 0.2,
      "team": {
        "id": 90,
        "name": "Some Team Name 1"
      }
    },
    {
      "allocation": 0.9,
      "team": {
        "id": 80,
        "name": "Some Team Name 2",
        "product": {
          "id": 20,
          "name": "Some Product Name 1"
        }
      }
    },
    {
      "allocation": 0.1,
      "team": {
        "id": 10,
        "name": "Some Team Name 3",
        "product": {
          "id": 22,
          "name": "Some Product Name 2"
        }
      }
    }
  ]
}

I tried multiple jolt spec but couldn't come up with the desired output. What should be the ideal jolt spec for this?

Answer 1

This spec should using shift operation should work:

[
  {
    "operation": "shift",
    "spec": {
      "item": {
        "name": "name",
        "allocDetails": {
          "items": {
            "*": {
              "allocation": "allocDetails[&1].allocation",
              "team": {
                "id": "allocDetails[&2].team.id",
                "name": "allocDetails[&2].team.name",
                "product": "allocDetails[&2].team.product"
              }
            }
          }
        }
      }
    }
  }
]

---

Edit #1:

The explanation: The shift operation spec defines where do we want to put the values from the input json in the result json.

1. Each key - value pair in the spec defines the source - target relation. For example (let's start from the simplest one): value from the ["item"]["name"] will land under the ["name"] key in the output JSON.
2. The

 "items": {
    "*": {
      ...
    }
 }

part says: "For each element of the array under the 'items' key do ..."

3. The ampersand operator "&X" lets us reference the key that is X levels above the LHS (the key in question). For example: Let's imagine we have the 57th element of the items array (counting from 0):

...
"name": "allocDetails[&2].team.name"
...

says: "Place the value found under the "name" key (that is in item["items"][56]["team"]["name"] in the 57th element of the array placed under the "allocDetails" key.

'*' matches the 57th element. '&2' lets us find out that the element of the array we are working on right now is the 57th element.

Have a look at the shift operation javadocs, especially at the "&" and "*" wildcards

---

Edit #2: considering the otherDetails comment: You could also approach it like this:

...
    "team": {
        "id": "allocDetails[&2].team.id",
        "name": "allocDetails[&2].team.name",
        "product": {
            "otherDetails": null,
            "*": "allocDetails[&3].team.product.&"
        }
    }
...

the above: puts all of the products' part keys (matched by the "*") to the key with the same name ("&") placed in the "allocDetails[&3].team.product" output json's key... with the exception of the "otherDetails" key.

Answer 2

Working jolt spec --

  {
    "operation": "shift",
    "spec": {
      "item": {
        "name": "name",
        "allocDetails": {
          "items": {
            "*": {
              "allocation": "allocDetails[&1].allocation",
              "team": {
                "id": "allocDetails[&2].team.id",
                "name": "allocDetails[&2].team.name",
                "product": {
                  "id": "allocDetails[&3].team.product.id",
                  "name": "allocDetails[&3].team.product.name"
                }
              }
            }
          }
        }
      }
    }
  }
]```