QueryDSL with DB2 fetching Nested Json object or Json array aggregation Response - json

Question

I am trying to fetch nested JSON objects and JSON List from Database using QueryDSL. I have used a native query with LISTAGG and JSON_OBJECT.
Native Query :
SELECT b.id,b.bankName,b.account,b.branch,(select CONCAT(CONCAT('[',LISTAGG(JSON_OBJECT('accountId' value c.accountId, 'name' value customer_name,'amount' value c.amount),',')),']') from CUSTOMER_DETAILS c where c.bankId = b.id) as customers from BANK_DETAILS b
BANK_DETAILS
+----+---------+---------+----------+
| id | BankName| account | branch |
+----+---------+---------+----------+
| 1 | bank1 | savings | branch1 |
| 2 | bank2 | current | branch2 |
+----+---------+---------+----------+
CUSTOMER_DETAILS
+----+-----------+---------------+----------+-----------+
| id | accountId | customer_name | amount | BankId |
+----+-----------+---------------+----------+-----------+
| 1 | 50123 | Abc1 | 150000 | 1 |
| 2 | 50124 | Abc2 | 25000 | 1 |
| 3 | 50125 | Abc3 | 50000 | 2 |
| 4 | 50126 | Abc4 | 250000 | 2 |
+----+-----------+---------------+----------+-----------+
Expected Output for the above tables
[{
"id": "1",
"bankName": "bank1",
"account": "savings",
"branch": "branch1",
"customers": [
{
"accountId": "50123",
"Name": "Abc1",
"amount": 150000
},
{
"accountId": "50124",
"Name": "Abc2",
"amount": 25000
},
]
},{
"id": "2",
"bankName": "bank3",
"account": "current",
"branch": "branch2",
"customers": [
{
"accountId": "50125",
"name": "Abc3",
"amount": 50000
},
{
"accountId": "50126",
"Name": "Abc4",
"amount": 250000
},
]
}]
i have tried with writing this native query in QueryDSL with the below multiple queries for make the same expected output with the forEach loop.
class Repository {
private SQLQueryFactory queryFactory;
public Repository (SQLQueryFactory queryFactory){
this.queryFactory = queryFactory;
}
public void fetchBankDetails(){
List<BankDetails> bankList = queryFactory.select(QBankDetails.bankDetails)
.from(QBankDetails.bankDetails);
bankList.forEach(bankData ->{
List<CustomerDetails> customerList = queryFactory.select(QCustomerDetails.customerDetails)
.from(QCustomerDetails.customerDetails)
.where(QCustomerDetails.customerDetails.bankId.eq(bankData.bankId));
bankData.setCustomerList(customerList)
});
System.out.println(bankList);
}
}
I need to improve my code and convert it into a single query using QueryDSL to return the expected output
Is there any other way or any suggestions?