Meta Transactions - Web3j

String jsonMessageString = Files.readString(Paths.get("src/main/resources/data.json").toAbsolutePath());
JSONObject jsonObject = new JSONObject(jsonMessageString);
jsonObject.getJSONObject("message").put("from", credentials.getAddress());
jsonObject.getJSONObject("message").put("nonce", nonce);
jsonObject.getJSONObject("message").put("data", encodedFunction);

String modifiedJsonString = jsonObject.toString();
Sign.SignatureData signature = Sign.signTypedData(modifiedJsonString, credentials.getEcKeyPair());