Generate JSON schema from Java class
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.
Java JSON Schema Generator: https://github.com/victools/jsonschema-generator
Creates JSON Schema (Draft 6, Draft 7 or Draft 2019-09) from Java classes using Jackson.
Use JJschema. It can generate draft 4 compliant JSON schemas. Refer this post http://wilddiary.com/generate-json-schema-from-java-class/ for details.
Though Jackson Json Schema module can too generate schema but it can, as of today, only generate draft 3 compliant schemas only.