How to use the JSON to Java
- Paste a JSON sample in the input — Java is already selected.
- Set the root type name and options such as optional fields and date detection.
- Copy the generated Java code into your project.
JSON to Java classes
Each JSON object becomes a Java class (or record) with typed fields; nested objects become their own classes and arrays become List<T>. Keys that aren’t valid Java identifiers are mapped with annotations, so the class works with Jackson (@JsonProperty) and Gson (@SerializedName).
Reading the JSON
With Jackson: new ObjectMapper().readValue(json, Root.class). Configure FAIL_ON_UNKNOWN_PROPERTIES to decide whether extra fields should be ignored. Whole numbers that may exceed 2³¹ are typed as long.
Private by design
The conversion runs entirely in your browser — API responses with customer or internal data are never uploaded.
Tools that pair well with the JSON to Java
- JSON to Types — Paste an API response and get ready-to-use models in 8 languages: TypeScript, Python (dataclass, TypedDict or Pydantic), Go, Java, C#, Kotlin, Swift and Rust.
- JSON Validator — Paste JSON to check whether it is valid.
- JSON Schema Validator — Paste a schema and some JSON to see exactly which values break which rule — or generate a starting schema from example data.
- Mock Data Generator — Create up to 10,000 rows of realistic test data — users, products, orders, addresses, companies or nested API records — or build your own schema.
Frequently asked questions
How are nested JSON objects converted to Java?
Each nested object becomes its own named classe, named after its key, and referenced from the parent. Arrays become typed lists of the element type.
What happens with fields that are missing or null in some items?
When you paste an array of objects, fields that are missing or null in some items are marked optional (nullable), so the generated code matches real API responses.
Is my JSON uploaded?
No. The conversion runs entirely in your browser, so API responses with private data never leave your device.
Can I install JSON to Java as a web app and use it offline?
Yes. JSON to Java is an installable web app (PWA) — installed from your browser, not downloaded from an app store. Click Install app at the top of this page in Chrome or Edge (Windows, macOS, Linux, ChromeOS) or on Android, use Share → Add to Home Screen on iPhone and iPad, or File → Add to Dock in Safari 17+ on a Mac. It then opens in its own window with its own icon, and because it runs entirely in your browser it keeps working offline. Firefox on desktop can’t install web apps. How installing works.