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Transform JSON with array objects into individual records – JOLT spec

I am working on Jolt transform feature in Apache Nifi. I am new to this and need help.
The input JSON can have several objects which contain multiple numerical arrays, that need to be flattened.

JSON Input:

[
  {
    "ABC": "aaaaa",
    "DEF": "bbbbb",
    "GHI": "ccccc",
    "JKL": "ddddd",
    "val1": [
      87.6,
      27.42
    ],
    "val2": [
      0.12,
      0.86
    ]
  },
  {
    "ABC": "ppppp",
    "DEF": "qqqqq",
    "GHI": "rrrrr",
    "JKL": "sssss",
    "val1": [
      92.38,
      64.48
    ],
    "val2": [
      1.04,
      0.22
    ]
  },
  ...
]

Expected Output:

[
  {
    "ABC": "aaaaa",
    "DEF": "bbbbb",
    "GHI": "ccccc",
    "JKL": "ddddd",
    "val1": 87.6,
    "val2": 0.12
  },
  {
    "ABC": "aaaaa",
    "DEF": "bbbbb",
    "GHI": "ccccc",
    "JKL": "ddddd",
    "val1": 27.42,
    "val2": 0.86
  },
  {
    "ABC": "ppppp",
    "DEF": "qqqqq",
    "GHI": "rrrrr",
    "JKL": "sssss",
    "val1": 92.38,
    "val2": 1.04
  },
  {
    "ABC": "ppppp",
    "DEF": "qqqqq",
    "GHI": "rrrrr",
    "JKL": "sssss",
    "val1": 64.48
    "val2": 0.22
  }
  ...
]

Please note that root array can have several objects.
Can anyone help here?
Thanks

Tags:

2

Answers


  1. 0

    You can use the below spec

    [
  {
    "operation": "shift",
    "spec": {
      "*": {
        "val1": {
          "*": {
            "@(2,ABC)": "[#4].&1.ABC",
            "@(2,DEF)": "[#4].&1.DEF",
            "@(2,GHI)": "[#4].&1.GHI",
            "@(2,JKL)": "[#4].&1.JKL",
            "@": "[#4].&1.val1"
          }
        },
        "val2": {
          "*": {
            "@": "[#4].&1.val2"
          }
        }
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "[]"
      }
    }
  }
]
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  2. 0

    You can handle the issue dynamically by putting the non-arrays into a common object, namely Others, while starting the transformation such as

    [
  {
    "operation": "shift",
    "spec": {
      "*": {
        "*": "&1.Others.&", // the attributes
        "val*": { // to group the components of the "val*" arrays starts here 
          "*": { // the indexes of the "val*" arrays
            "@": "&3.val[&1].&2"
          }
        }
      }
    }
  },
  {
    "operation": "shift",
    "spec": {
      "*": {
        "val": {
          "*": {
            "@2,Others": { "*": "&4[&1].&" }, // go two levels up the tree to grab the values from the "val" array
            "*": "&3[&1].&"
          }
        }
      }
    }
  },
  { // get rid of the keys of the arrays respectively
    "operation": "shift",
    "spec": {
      "*": {
        "*": "[]"
      }
    }
  }
]
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