Expression.get("PRODUCT_ID").getField("PRODUCT_NAME").like("Freezer")

Question

Hi! All,
In ServiceRequests Table Product_Id is a an attribute, and Product Information like Product Name , Product Description is in Products Tale. The relation between theses is Product_Id column in ServiceRequests Table.
Getting the Product_Id , I need to get the Names of the Produts that have Freezer in the first word of their name.
for that I'm doing,
ReadAllQuery raq= new ReadAllQuery(ServiceRequests.class);
raq.setReferenceClass(ServiceRequests.class);
ExpressionBuilder builder = new ExpressionBuilder();
raq.setSelectionCriteria(builder.get("PRODUCT_ID").getField("PRODUCT_NAME").like("Freezer"));
// raq.setSelectionCriteria( builder.getField("PRODUCT_ID").greaterThan(100));
Vector servicelist = (Vector) session.executeQuery(raq);
I'm getting : TopLink Exception -- 6015 Invalid Query key[Product_Id]
Can some one tell me where I am doing wrong, or was it a wrong way to do to get the desired result?
Thanking you in Advance,
Samba

Answer 1

I didn't notice before you're using get(..) and getField(..). If you've got your classes mapped you shouldn't have to use getField(..). By capturing your object-relational mappings in TopLink, you enable querying based on the attributes of objects instead of the database columns. This helps decouple your code from the data model. For example, I can write the following expression given the classes below:
ExpressionBuilder employee = new ExpressionBuilder();
Expression where = employee.get("address").get("streetName").equal("Main");
emp = (Emp)session.readObject(Emp.class, where);
public class Emp{
   long empId;
   Address address;
public class Address {
   long addressId;
   String streetName;
...See how I reference the address attribute of an Emp and put a constraint on the streetName? This expression will result in a SQL join based on the table reference info I provided in the TopLink one-to-one mapping between Emp and Address. I don't use the column names in my query at all. The are encapsulated in the TopLink mappings.
I think this is similar to the problem you're facing. Does this help?
--Shaun