JSONPath Library for Play

Apr 15 2014

I’ve been working on a platform that transforms, composes, and serves data. As part of this effort, I’ve developed a library for Play that performs a JSONPath query on a Play JsValue. You can learn about JSONPath by reading Stefan Goessner’s blog post on the subject.

I use Gatling’s jsonpath library to parse the JSONPath expression. I then fold over the tokens, performing a pattern match on each to construct the apporpriate JsValue. This parser supports all queries except for queries that rely on expressions of the underlying language like $..book[(@.length-1)]. However, there’s usually a ready workaround as you can execute the same query using $..book[-1:].


Here’s a scala worksheet which traces the examples on Stefan’s post:

Deviation from JSONPath

One conscious choice I made as far as deviating from JSONPath is to always flatten the results of a recursive query. Using the bookstore example, typically a query of $..book will return an array with one element, the array of books. If there was another book array somewhere in the document, then $..book will return an array with two elements, both arrays of books. However, if you were to query $..book[2] for our example, you would get the second book in the first array, which assumes that the $..book result has been flattened. In order to make recursion easier and the code simpler, I always flatten the result of recursive queries regardless of the context.

If you have any questions, comments, or suggestions please let me know. I hope to be introducing an early iteration of my data platform shortly so stay tuned!

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