EDIT: as pointed out by commenters, module is being deprecated, not maintained. So, Caveat Emptor etc

One such tool is Jackson JSON Schema module:

https://github.com/FasterXML/jackson-module-jsonSchema

which uses Jackson databind's POJO introspection to traverse POJO properties, taking into account Jackson annotations, and produces a JSON Schema object, which may then be serialized as JSON or used for other purposes.

You can generate fake java-objects and then map them to JSON.

POJOs

If you already have the POJOs matching the schema, then we can skip this step. If no, to generate a POJO from the schema, for example, can be used this library: jsonschema2pojo.

Fake objects

Generating of objects with fake data can be done with a special library, some of them are listed here:

• easy-random
• podam
• java-faker

Generating JSON

It's prettry simple and can be done with Jackson:

ObjectMapper objectMapper = new ObjectMapper();
ObjectWriter prettyPrinter = objectMapper.writerWithDefaultPrettyPrinter();
String json = prettyPrinter.writeValueAsString(yourFakeObject);

My team and I have created an online tool that allows you to parse JSON schema and generate an array of JSON data that complies to the schema. You can save it as .json file and parse it to your app with a Java parser.

The tool is called Mock turtle - https://mockturtle.net .