How to handle JSON with dynamic or unknown keys using GSON in Kotlin Android

How to handle JSON with dynamic or unknown keys using GSON in Kotlin Android.

Handling JSON with Dynamic or Unknown Keys using GSON in Kotlin Android

Introduction

When working with JSON data in an Android application, it is common to encounter situations where the keys in the JSON object are dynamic or unknown. In such cases, it can be challenging to parse the JSON data using a traditional approach. However, with the help of GSON library, handling JSON with dynamic or unknown keys becomes much easier. In this tutorial, we will learn how to handle JSON with dynamic or unknown keys using GSON in Kotlin Android.

Prerequisites

To follow along with this tutorial, you should have a basic understanding of Kotlin and Android development. You should also have GSON library added to your project. If you haven't added GSON to your project yet, you can do so by adding the following dependency to your app-level build.gradle file:

implementation 'com.google.code.gson:gson:2.8.6'

Parsing JSON with Dynamic or Unknown Keys

To parse JSON with dynamic or unknown keys using GSON, we need to define a custom deserializer. The deserializer will handle the dynamic or unknown keys and map them to appropriate Kotlin objects. Here's how we can do it:

1. Create a new Kotlin class for the custom deserializer. Let's name it DynamicKeyDeserializer:

import com.google.gson.*
import java.lang.reflect.Type

class DynamicKeyDeserializer : JsonDeserializer<Map<String, Any>> {
    override fun deserialize(
        json: JsonElement?,
        typeOfT: Type?,
        context: JsonDeserializationContext?
    ): Map<String, Any> {
        val map = mutableMapOf<String, Any>()
        json?.let {
            val jsonObject = it.asJsonObject
            for (entry in jsonObject.entrySet()) {
                val key = entry.key
                val value = entry.value
                map[key] = context?.deserialize(value, Any::class.java) ?: ""
            }
        }
        return map
    }
}

2. Now, let's create a helper function to parse the JSON using GSON and the custom deserializer:

import com.google.gson.GsonBuilder

fun parseJsonWithDynamicKeys(jsonString: String): Map<String, Any> {
    val gson = GsonBuilder()
        .registerTypeAdapter(Map::class.java, DynamicKeyDeserializer())
        .create()
    return gson.fromJson(jsonString, Map::class.java)
}

3. Finally, let's use the helper function to parse a JSON string with dynamic or unknown keys:

val jsonString = "{ \"key1\": \"value1\", \"key2\": 123, \"key3\": [1, 2, 3] }"
val jsonData = parseJsonWithDynamicKeys(jsonString)

// Accessing the values
val value1 = jsonData["key1"] as? String
val value2 = jsonData["key2"] as? Int
val value3 = jsonData["key3"] as? List<*>

In the example above, we defined a custom deserializer DynamicKeyDeserializer that implements the JsonDeserializer interface. This deserializer converts the JSON object with dynamic keys into a Map<String, Any>. We then registered this deserializer with GSON using the registerTypeAdapter method. Finally, we used the parseJsonWithDynamicKeys helper function to parse the JSON string and access the values using dynamic keys.

Conclusion

In this tutorial, we learned how to handle JSON with dynamic or unknown keys using GSON in Kotlin Android. We created a custom deserializer to handle the dynamic keys and map them to appropriate Kotlin objects. By using GSON's deserialization capabilities, we can easily parse JSON data with dynamic or unknown keys in our Android applications.