Master Detail table mapping

[Michelle Nicholes]

I have a master table people and detail places. In my DAO, I query for all people and I can easily use a Class implementing RowMapper to map each row .

Is there a way to also get the list of places for each person while i am getting each person without having to reiterate through the list after i get the list of people?

[Jayesh A Lalwani]

Yes, you can join the 2 tables in a SQL, and sort them by People's ID. Define a "PeoplePlaces" class that contains the columns from both tables, and in your RowMapper, return the PeoplePlaces object. In your DAO method, the queryForObject method will return a list of PeoplePlaces objects that will be sorted by peopleId. You can then iimplement an algorithm that iterates over the PeoplePlaces and seperates the People from the Places

OR

You can use an ORM layer like JPA/Hibernate, and the ORM layer will do all this work for you. You don;t have to reinvent the wheel.

[Michelle Nicholes]

Is there a performance hit to use JPA, hibernate?
Prior to learning Spring, I was using EJBs and I was using JPA with the EJBs.
but I was told the huge websites which performance is an issue, they used Spring which is why I am now learning Spring.
So, with that said, which one of your suggestions do the high performance sites use?

[Jayesh A Lalwani]

With JPA, it's all about how you design the ORM layer. If you put a lot of eager one to many mappings, performance will suffer. You need to look at the raw sqls thT hibernate runs to optimize your entity mapping