How to Create a POJO and Convert It into Acceptable JSON for Cloud Firestore REST API

Learn how to create a `POJO` in Java for converting into the correct `JSON` format needed by the Cloud Firestore REST API when using Retrofit.
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How to Create a POJO and Convert It into Acceptable JSON for Cloud Firestore REST API

When working with the Cloud Firestore REST API, sending data in the correct JSON format is crucial. If you're implementing this with Android Java, using Retrofit makes the process easier, but you might encounter a few challenges, particularly with how to structure your Plain Old Java Object (POJO). This guide will guide you through the process of creating a POJO that can be converted into the right JSON format for the Firestore API.

The Problem

Imagine you're working on an app that tracks locations and you need to send latitude and longitude data to Firestore. The JSON body for the API request looks like this:

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Now, when you use Retrofit to send your POJO to the API, you find that your generated JSON doesn't match the required structure. Instead of including "doubleValue", it simply returns the numerical values directly, like so:

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The question is: how do you create a POJO that ensures the JSON follows the required structure?

The Solution

Step 1: Update Your POJO Structure

To achieve the desired JSON output, you will need to restructure your POJO. Instead of directly mapping longitude and latitude as double, create nested POJO classes that include an additional attribute for "doubleValue". Here's how you can do it:

Create a Response Model Class:

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Define the Fields Class:

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Create the Latitude and Longitude Classes:

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Step 2: Update the Retrofit API Interface

Next, you will need to modify your Retrofit API interface to use the new response model:

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Step 3: Call the API with the Updated Model

Finally, ensure that when you call the API, you instantiate your objects properly, ensuring the longitude and latitude values are encapsulated within their respective classes, as shown:

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By following these steps, you should see your JSON formatted correctly according to Firestore’s requirements, with the necessary field transformations included.

Conclusion

Creating a POJO for the Cloud Firestore REST API can be a bit tricky, but with the right structure, you can ensure that your data is sent in the required JSON format. This guide provided the steps necessary to create a nested POJO structure that accurately transforms your latitude and longitude values into "doubleValue" format for Firestore. Happy coding!