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Introduction

As described in README.md a transformer semantically transforms one JSON object into another. For this purpose a programming language or a transformation language such as JSONata can be used.

Short description of model transformation languages in general:

A model transformation, which is essentially a program which operates on models, can be written in a general-purpose programming language, such as Java. However, special-purpose model transformation languages can offer advantages, such as syntax that makes it easy to refer to model elements.

Source: Wikipedia

Due to its focus on JSON objects and its simplicity, JSONata is the recommended transformation language for creating a transformer.

JSONata Overview

  • Is a Lightweight query and transformation language for JSON data
  • Helps to extract specific meaningful data from JSON data using a simple logic
  • Supports more than 20 operators
  • Includes numerous functions such as string-, numeric-, array- and object-functions

In the following some exemplary functions as well as a general JSONata mapping example is provided.

For further information of JSONata please visit the official JSONata documentation, which also includes a listing of all supported functions.
If you want to test JSONata check out the JSONata Excerciser.

Exemplary Functions

String Functions

Find and replace of a pattern within a string and replace it with a certain value:

$replace(str, pattern, replacement [, limit])

Example:

$replace("Have a nice day", "day", "week") ==> "Have a nice week"

Numeric Functions

Sum the values of an array:

$sum(array)

Example:

$sum([1,1,3,5]) ==> 10

Array Functions

Concatenate the values of two array:

$append(array1, array2)`

Example:

$append(["This","is","a"], ["JSONata","example"]) ==> ["This", "is", "a", "JSONata", "example"]

Exemplary JSONata Transformation

The following example aims to provide an overview of the simplicity of JSONata.
For reasons of clarity and comprehensibility the exemplary JSON objects are simplified.

The JSON object that is used as input:

"alias": "mropen",
"email": "connected@openintegrationhub.org",
"salutation": "mr.",
"title": "Prof. Dr.",
"firstname": "Open",
"middlename": "Integration",
"lastname": "Hub",
"phone": [
  {
    "number": "0151123456"
  },
  {
    "number": "0177654321"
  }
],
"gender": "male",
"signupdate": "2017-07-01",
"description": "open source project",
"weight": "80,3",
"age": "30"

The following JSONata expression transforms the input into the needed JSON object

"alias": alias,
"fullname": title & ' ' & firstname & ' ' & middlename & ' ' & lastname,
"memberSince": signupdate,
"Surname": lastname,
"Name": firstname,
"Middlename": middlename,
"Academictitle": title,
"Phonenumbers": phone.number,
"description": $lowercase(description),
"weight": $number($replace(weight, "," , ".")),
"age": $number(age)

The following JSON object results from the transformation:

"alias": "mropen",
"fullname": "Prof. Dr. Open Integration Hub",
"memberSince": "2017-07-01",
"Surname": "Hub",
"Name": "Open",
"Middlename": "Integration",
"Academictitle": "Prof. Dr.",
"Phonenumbers": [
  "0151123456",
  "0177654321"
],
"description": "open source project",
"weight": 80.3,
"age": 30