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Discover how to effectively send `null` values with Retrofit 2 in your Android application. Learn the steps and code snippets you need for seamless API integration.
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How to Send null Values to Server Using Retrofit 2 in Android

When working with APIs in your Android application using Retrofit 2, you might encounter cases where you need to send null values to the server. This can often be tricky since Retrofit, by default, ignores fields that hold null values. In this guide, we’ll walk through a common scenario and discuss how to effectively send null values using Retrofit 2.

The Problem

Imagine you are developing an application where you need to update share details on the server. You have a data class, UpdateShare, that contains a field named expireAt, which may need to be sent as null under certain circumstances. Below is a snippet of how your API interface is defined:

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Your UpdateShare class looks something like this:

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In scenarios where expireAt needs to be null, Retrofit will skip sending this field to the server, which can lead to issues since the expected data structure may not be intact. But how can this problem be resolved?

The Solution

The solution lies in using a custom Gson instance during the Retrofit setup. By configuring the Gson builder to serialize null values, you can ensure that fields with null are included in the JSON payload sent to the server.

Step-by-Step Implementation

Add Gson Dependencies: Ensure you have the necessary dependencies in your build.gradle file for Retrofit and Gson.

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Configure Retrofit to Serialize Nulls: Update your Retrofit instance creation code to include serializeNulls() in the GsonBuilder.

Here is how you can do it:

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Use the Updated Retrofit Instance: With this configuration, you can now safely send your UpdateShare object, even when expireAt is set to null.

Example

Here’s how you might update your share with expireAt as null:

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Conclusion

Sending null values in Retrofit 2 is not just a matter of configuring your API calls; it requires a proper setup of the Gson instance to ensure that all necessary data, including null values, is conveyed to the server as required. By following the steps outlined above, you should be able to handle such cases in your Android applications seamlessly. Happy coding!