Well, I finally get it with following code 
String json = "my_json_value";
Reader reader = new StringReader(json);
JsonpMapper jsonpMapper = getClient()._transport().jsonpMapper();
JsonProvider jsonProvider = jsonpMapper.jsonProvider();
JsonData jd = JsonData.from(jsonProvider.createParser(reader), jsonpMapper);
BulkRequest.Builder br = new BulkRequest.Builder();
br.operations(op -> op.index(idx -> idx.index(index).id(id).document(jd)));
BulkRequest request = br.build();
BulkResponse response = getClient().bulk(request);