This article is the Java part of a series whose main article is How to build a language binding for a web API which you should read before this one to get general background information about implementing a language binding.
Recently I’ve worked with a web API, the Cometdocs API, in order to use their converter of documents, particularly for automating some conversions from PDF documents to Excel spreadsheets for data extraction.
I wanted to use this API from my two favorite development platforms: Java and .Net/C#, so I needed to build what is called a language binding, i.e. a small library that acts as a proxy between the application code and the web API.
The development of these two bindings was really interesting from a technical point of view, and I’ve learned a bunch of things during the process.
I’d like to share the interesting stuff with you, it should be of interest even if you don’t have any plan for interacting with a web API because all the technologies and techniques I’ve used (the HTTP protocol, JSON data binding, SSL/TLS…) are applicable to other types of developments.
Today if you ever need to consume a web API, or produce one, chances are you’ll need to use JSON.
And there is good reasons why JSON has become so prevalent in the web world:
So whatever the language and platform you’ll use you’ll need a strong JSON parsing component.
In the Java world there is at least two good candidates: Gson and Jackson.
In this article I’ll illustrate how to use Gson: I’ll start with a (not so) simple use case that just works, then show how you can handle less standard situations, like naming discrepancies, data represented in a format not handled natively by Gson or types preservation.