Jolt.Net 1.0.0

Jolt.Net

JSON to JSON transformation library written in c# where the "specification" for the transform is itself a JSON document. This is a c# port of the original Java version from https://github.com/bazaarvoice/jolt. JSON handling is provided by Newtonsoft Json

Useful For

1. Transforming JSON data from ElasticSearch, MongoDb, Cassandra, etc before sending it off to the world
2. Extracting data from a large JSON documents for your own consumption

Overview

Jolt :

• provides a set of transforms, that can be "chained" together to form the overall JSON to JSON transform.
• focuses on transforming the structure of your JSON data, not manipulating specific values
  • The idea being: use Jolt to get most of the structure right, then write code to fix values
  • consumes and produces Newtonsoft.Json objects (JToken, JArray, JObject, ...)

Stock Transforms

The Stock transforms are:

shift       : copy data from the input tree and put it the output tree
default     : apply default values to the tree
remove      : remove data from the tree
sort        : sort the Map key values alphabetically ( for debugging and human readability )
cardinality : "fix" the cardinality of input data.  Eg, the "urls" element is usually a List, but if there is only one, then it is a String

Each transform has it's own DSL (Domain Specific Language) in order to facilitate it's narrow job.

Currently, all the Stock transforms just effect the "structure" of the data. To do data manipulation, you will need to write c# code. If you write your c# "data manipulation" code to implement the Transform interface, then you can insert your code in the transform chain.

The out-of-the-box Jolt transforms should be able to do most of your structural transformation, with custom c# implementing your data manipulation.

Documentation

Jolt Slide Deck : covers motivation, development, and transforms.

Javadoc explaining each transform DSL :

• shift
• default
• remove
• cardinality
• sort
• fully qualified c# type name: Class implements the ITransform or IContextualTransform interfaces, and can optionally be SpecDriven (abstract base class)
  • Transform interface
  • SpecDriven
    • where the "input" is the JSON data as a JToken

Running a Jolt transform means creating an instance of Chainr with a list of transforms.

The JSON spec for Chainr looks like : unit test.

The c# side looks like :

var json = JObject.Parse(File.ReadAllText("/path/to/chainr/spec.json"));
var output = chainr.Transform(input);

return output;

Demo

There is a demo available at jolt-demo.appspot.com. You can paste in JSON input data and a Spec, and it will post the data to server and run the transform.

Note

• it is hosted on a free Google App Engine instance, so it may take a minute to spin up.
• it validates in input JSON and spec client side.