[MariaDB] list inside list. row has multiple data

 SELECT

t1.id

,JSON_ARRAYAGG(

      JSON_OBJECT(

        't2_id', t2.id,

        't2_title', t2.title

      )

    ) AS t2_json

FROM t_test1 t1

LEFT JOIN t_test2 t2 ON t2.test1_id=t1.id

 GROUP BY t1.id

;

import com.fasterxml.jackson.core.type.TypeReference;

import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonToMapListExample {

    public static void main(String[] args) throws Exception {

        String jsonData = "[{\"t2_id\": 1, \"t2_title\": \"t21\"},{\"t2_id\": 2, \"t2_title\": \"t22\"}]";

        ObjectMapper objectMapper = new ObjectMapper();

        List<Map<String, Object>> dataList = objectMapper.readValue(jsonData, new TypeReference<List<Map<String, Object>>>() {});

        // Now you can work with the List<Map<String, Object>> data

        for (Map<String, Object> map : dataList) {

            System.out.println("t2_id: " + map.get("t2_id"));

            System.out.println("t2_title: " + map.get("t2_title"));

        }

    }

}