multiple one-to-many relations ResultSetExtractor

Question

Let\'s say I have an object with two different one-to-many relations. Much like:

Customer 1<->M Brands and Customer 1<->M Orders

Answer 1

I assume the model described by James Jithin in his answer:

TBL_CUSTOMER
------------
CUSTOMER_ID
CUSTOMER_ACCOUNT_NO
CUSTOMER_NAME

TBL_CUSTOMER_BRANDS
-------------------
CUSTOMER_BRAND_ID            - UK
BRAND_NAME
CUSTOMER_ID                  - FK

TBL_ORDERS
-------------------
ORDER_ID                     - UK
CUSTOMER_ID                  - FK

Instead of going for one Query, I would suggest the following three:

SELECT CUS.* FROM TBL_CUSTOMER CUS 

SELECT BRANDS.CUSTOMER_ID, BRANDS.CUSTOMER_BRAND_ID, BRANDS.BRAND_NAME FROM TBL_CUSTOMER_BRANDS BRANDS

SELECT ORDERS.CUSTOMER_ID, ORDERS.ORDER_ID FROM TBL_ORDERS ORDERS 

Your RowCallbackHandlers would become:

private class CustomerRowCallbackHandler  implements RowCallbackHandler {

    private final Map customerMap;

    public BrandRowCallbackHandler(Map customerMap) { this.customerMap = customerMap}

    public void processRow(ResultSet rs) throws SQLException {
            Long id = rs.getLong("CUSTOMER_ID");
            Customer customer = map.get(id);
            if(customer == null){
                customer = new Customer();
                customer.setId(id);
                customer.setName(rs.getString("CUSTOMER_NAME"));
                customer.setAccountNumber(rs.getLong("CUSTOMER_ACCOUNT_NO"));
                map.put(id, customer);
                    }
    }
}

private class BrandRowCallbackHandler implements RowCallbackHandler {

    private final Map customerMap;

    public BrandRowCallbackHandler(Map customerMap) { this.customerMap = customerMap}

    public void processRow(ResultSet rs) throws SQLException {
            Long id = rs.getLong("CUSTOMER_ID");
            Customer customer = map.get(id);
            if(customer != null){
                List brandList = customer.getBrands();
                if(brandsList == null) {
                    brandsList = new ArrayList();
                    customer.setBrands(brandsList);
                }
                Brand brand = new Brand();
                brand.setId(rs.getLong("CUSTOMER_BRAND_ID"));
                brand.setName(rs.getString("CUSTOMER_BRAND_NAME"));
                brandsList.add(brand);
            } 
    }
}

private class OrderRowCallbackHandler implements RowCallbackHandler {

    private final Map customerMap;

    public OrderRowCallbackHandler(Map customerMap) { this.customerMap = customerMap}

    public void processRow(ResultSet rs) throws SQLException {
            Long id = rs.getLong("CUSTOMER_ID");
            Customer customer = map.get(id);
            if(customer != null){
                List ordersList = customer.getOrders();
                if(ordersList == null) {
                    ordersList = new ArrayList();
                    customer.setOrders(ordersList);
                }
                Order order = new Order();
                order.setId(rs.getLong("ORDER_ID"));
                ordersList.add(order);
            }
    }
}