Session.readObject(..) v/s ReadObjectQuery

Question

Is there any difference between using
session.readObject(DAO.class, expr) and
ReadObjectQuery(DAO.class, expr)?
Thanks,
Rajiv

Answer 1

Well, they're a very easy way to manage query re-use, and therefore reduce garbage collection.
Additionally, since named query construct can be separated from named query execution, named queries provide an easy way to abstract toplink in a service layer. All your service layer would provide would be mechanisms for executing queries by name. Your service layer could then pass through to toplink.
There are lots of benefits to this:
1. Query reuse. Implies less garbage which implies faster performance.
2. Abstraction. No toplink code outside the service layer (as you call it) (excepting perhaps valueholders).
3. Cleanliness. Your code has one mechanism for executing queries. By name. Why have lots of confusing ways to do the same thing?
4. Localization of queries. A surprisingly overlooked benefit. Named queries will normally be defined together, in one code location (eg 1 package). This makes it very easy to identify badly performing queries and re-write them without having to play hunt the expression builder.
Christian