gojsonata

gojsonata

Execute JSONata query and transformation expressions in Golang.

Problem Statement

We want a generic solution for transfomation of structured data in Golang. XSLT is the most advanced solution for transforming XML data, but it is not well supported by Golang. JSONata is an elegant solution for transforming JSON data, but it supports only JavaScripts.

This project describes how to execute JSONata transformation expressions in Golang. Following are the tools used to make it work.

• otto - A JavaScript interpreter in Go. It supports only ES5 syntax.
• JSONata - query and transformation language for JSON.
• traceur - JavaScript transpiler for generating ES5 code from ES6+ code.
• go-bindata - Go utility for converting any file into Golang source code.

We provide scripts to transpile JSONata library to ES5, and then convert the resulting files into Golang source code.

We then implement a Golang utility that you can use to transform any JSON data using JSONata expression. This utility creates an otto JavaScript interpreter, and preloads JSONata libraries when the utility is loaded. Thus, any complex data transformation request can be handled by a simple function call with input JSON data and an JSONata expression.

Installation

Install Go version 1.11.x and set GOPATH environment variable.

Install GNU make. For ubuntu, e.g., use the following commands

sudo apt update
sudo apt install make
sudo apt install make-guile

Install Node.js and npm. For ubuntu, e.g., use the following command

sudo apt install nodejs npm

Clone this project, then setup and test it as follows:

export PATH=${GOPATH}/bin:${PATH}
go get -u -d github.com/yxuco/gojsonata
cd ${GOPATH}/src/github.com/yxuco/gojsonata
make

Examples

Following Golang example shows the execution of a JSONata expression vehicle-expr.txt on the input data vehicle.json, which created an output result of different schema.

	data, _ := ioutil.ReadFile("./tests/vehicle.json")
	expr, _ := ioutil.ReadFile("./tests/vehicle-expr.txt")
	result, _ := Transform(string(data), string(expr))
	fmt.Printf("result value: %s\n", result)

A simpler transformation can also be done as follows:

	value, _ := RunScript(
		`var data = {
		  example: [
		    {value: 4},
		    {value: 7},
		    {value: 13}
		  ]
	    };
	  
	    var expression = jsonata('$sum(example.value)');
	    expression.evaluate(data);`)
	result, _ := value.ToInteger()  // result = 24

The file jsengine_test.go shows more Golang examples.

You may also use the motto command-line tool to test JSONata transformations, which is demonstrated by the following commands in the Makefile.

    make motto

For quick interactive testing of JSONata scripts, you can use http://try.jsonata.org/ to edit JSON data and JSONata scripts, and view the results immediately.