Transform/round-off decimal numbers in Nifi

Question

I am trying to POST a JSON file (using Apache NiFi) onto an app that only accepts values with max 10 decimal places.

JSON format:

{
  "timestamp" : "2016-04-17",
  "zoom" : 13,
  "dc" : 100,
  "CloudCoverPercentage" : 74.707,
  "mean" : 0.18735192480231655,
  "num" : 127,
  "FirstQuartile" : 0.142807444773004,
  "median" : 0.17882054533925174,
  "max" : 0.32004310344827586,
  "min" : 0.059890294413970674,
  "ThirdQuartile" : 0.22603810187853218,
  "StandardDeviation" : 0.06846369990524923
}

Question: How do I transform each decimal value in Apache Nifi, so it would only have 10 decimal places? I read somewhere that JoltTransformJSON can be used for this. How do I write the Jolt Spec for this kind of operation?

Answer 1

You can use UpdateRecord with a jsonReader(Infer Schema), JsonSetWriter (Inherit Schema)

Input:

{
  "timestamp" : "2016-04-17",
  "zoom" : 13,
  "dc" : 100,
  "CloudCoverPercentage" : 74.707,
  "mean" : 0.18735192480231655,
  "num" : 127,
  "FirstQuartile" : 0.142807444773004,
  "median" : 0.17882054533925174,
  "max" : 0.32004310344827586,
  "min" : 0.059890294413970674,
  "ThirdQuartile" : 0.22603810187853218,
  "StandardDeviation" : 0.06846369990524923
}

Output:

[ {
  "timestamp" : "2016-04-17",
  "zoom" : 13,
  "dc" : 100,
  "CloudCoverPercentage" : 74.707,
  "mean" : 0.18735192480231655,
  "num" : 127,
  "FirstQuartile" : 0.142807444773004,
  "median" : 0.1788205453,
  "max" : 0.32004310344827586,
  "min" : 0.059890294413970674,
  "ThirdQuartile" : 0.22603810187853218,
  "StandardDeviation" : 0.06846369990524923
} ]