How to Use GSON with Kotlin Data Classes for JSON Serialization

How can I specify JSON keys for properties in Kotlin data classes with GSON, similar to the @SerializedName annotation in Java?

data class Topic(val id: Long, @SerializedName("name") val name: String)

GSON is a popular Java library used to convert Java objects into JSON and vice versa. While Kotlin does not provide @SerializedName directly within the data class syntax, there are effective ways to achieve similar functionality when deserializing JSON.

import com.google.gson.annotations.SerializedName\n\ndata class Topic(\n    @SerializedName("id") val id: Long,\n    @SerializedName("name") val name: String\n)\n\n// Example deserialization \nval json = "{ \"id\": 1, \"name\": \"Kotlin\" }"\nval topic = Gson().fromJson(json, Topic::class.java)

Causes

• GSON uses reflection for JSON field mapping, which doesn’t account for Kotlin's stricter type system.
• Data classes in Kotlin do not have an explicit annotation for JSON key mapping like Java's @SerializedName.

Solutions

• Use the `@SerializedName` annotation from the Gson library directly on the properties of the data class.
• Utilize GSON's `FieldNamingPolicy` for custom naming conventions, if applicable, rather than annotating each property.

Mistake: Forgetting to include GSON annotations in the data class properties.

Solution: Make sure to annotate fields with `@SerializedName` when needed.

Mistake: Assuming GSON will handle Kotlin nullability by default.

Solution: Always test and validate deserialization, as GSON does not enforce Kotlin's nullability.