JSON Forge
100% Client-Side: your data is never sent to a server

JSON to Java

Generate Java records with Jackson @JsonProperty annotations from a JSON sample. Nested objects become their own records and arrays become List<T>.

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Paste or type JSON on the left to explore it as a tree.
Empty🔒 Processed locally in your browser

How to convert JSON to Java classes

  1. Paste your JSON into the editor.
  2. Open the Code tab and choose Java.
  3. Copy the records into your project and read data with ObjectMapper.readValue.

Records instead of boilerplate classes

Java 16 and newer support records, which give you an immutable class with constructor, accessors, equals and hashCode in one line. They work with Jackson 2.12 and later, so the output stays short and readable.

Type mapping

Strings become String, whole numbers Long, decimals Double and booleans Boolean, using boxed types so missing values can be null. Arrays become List<T>. Mixed or unknown values fall back to Object. Keys that are not valid camelCase Java identifiers are renamed and annotated with @JsonProperty.

What is JSON?

JSON (JavaScript Object Notation) is a lightweight, text-based data format that is easy for people to read and for machines to parse. It is the de facto standard for web APIs, configuration files and data exchange between services. A JSON document is built from just six value types: objects, arrays, strings, numbers, booleans and null.

{
  "name": "Ada",
  "age": 36,
  "admin": true,
  "skills": ["math", "code"],
  "address": { "city": "London" },
  "manager": null
}

JSON is stricter than JavaScript object literals: keys and strings must use double quotes, trailing commas are not allowed and comments are not part of the specification (RFC 8259).

Why format JSON?

APIs usually return minified JSON on a single line, which is efficient for machines but unreadable for people. Formatting (also called pretty printing or beautifying) adds consistent indentation and line breaks so that you can scan the structure, spot mistakes and review changes. Minifying does the opposite and strips whitespace to reduce size.

Frequently asked questions

Which Java version is required?

Java 16 or later for records, and Jackson 2.12 or later to deserialize them.

Is my JSON uploaded to a server?

No. Parsing, validation, formatting, diffing and code generation all run inside your browser, using a Web Worker. Your data is never sent to any server, which makes the tool safe for API responses, configuration files and other sensitive payloads.

Does it work offline?

Yes, after the first visit. The editor and tools are stored in your browser, so you can use them without a connection. Only the TypeScript, CSS and HTML language workers used for extra highlighting in the Code tab are downloaded the first time you use them.

How large a JSON file can I open?

Files of 20 MB and more work. Parsing happens off the main thread and the tree view is virtualized, so only the rows you can see are rendered. The editor switches to a lighter mode for very large documents.

What is the difference between formatting and minifying JSON?

Formatting (pretty printing) adds line breaks and indentation so people can read the data. Minifying removes all optional whitespace to make the payload as small as possible for network transfer or storage. Both produce identical data.

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