JSON to Kotlin Data Class

A Kotlin data class is a special class that holds data. It automatically generates equals(), hashCode(), toString(), and copy() implementations, making it the idiomatic way to represent API response bodies, database models, and DTOs in Kotlin.

When consuming REST APIs in Android or Kotlin backend projects, you need data classes that match the JSON structure. Writing these by hand for complex JSON responses is tedious. This tool generates all the data classes from your JSON, including nested classes, proper type mappings, and @JsonProperty annotations for snake_case keys.

Input JSON:

{
  "id": 1,
  "first_name": "Alice",
  "is_active": true,
  "score": 9.5,
  "address": { "city": "Berlin", "zip": "10115" }
}

Generated Kotlin data classes:

import com.fasterxml.jackson.annotation.JsonProperty

data class Address(
    val city: String,
    val zip: String
)

data class Root(
    val id: Long,
    @JsonProperty("first_name")
    val firstName: String,
    @JsonProperty("is_active")
    val isActive: Boolean,
    val score: Double,
    val address: Address
)

// build.gradle.kts
implementation("com.fasterxml.jackson.module:jackson-module-kotlin:2.18.+")

Or use Spring Boot's built-in Jackson: no extra config needed.