2013-11-21 09:11:00
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When to use Dao classes like DaoFilterCriteria, ShipmentHeaderRow etc
and when to use Model data service?
For example,
DaoFilterCriteria filter = new DaoFilterCriteria();
List<ShipmentHeaderRow> shipmentLegs = getDaoAccessor().getRows(ShipmentHeaderRow.class, filter);
fetches ShipmentHeaderRows,
whereas
ModelDataService mds = Services.get(ModelDataService.class)
List<Shipment> shipments = mds.read(Shipment.class, context, params, modelQueryComponentArray)
fetches Shipments.
What is the difference between using ShipmentHeaderRow and Shipment?
Also what is the difference between using ( MDS or SqlService ) and Dao/DaoFilterCriteria etc classes?
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2013-11-21 10:11:00
Don't use DAO for any new code. It's deprecated.
As far as MDL versus SqlService, here's what you should think about:
Characteristics of SqlService:
- Doesn't apply permissions (can be a good or bad thing for you depending on the situation)
- Can select just one or two fields
- Can do arbitrary joins, basically execute any SQL
- Returns loosely typed "SqlRow" objects
Characteristics of ModelDataService:
- Applies permissions
- Automatically selects all fields
- Can do arbitrary joins in where clause, but not in select
- Returns strongly typed Model objects
In general, I would think you would want to use ModelDataService in cases where we used DAO in the past. One key difference is, the default behavior of MDS is to return a level plus all its child levels. This is expensive for Shipments with many Lines. Consult the MDS javadocs to see how you can ask it to return the header only.