I often need to display a read-only list of sumary data for multiple entries on the screen to allow a user to pick one item to edit e.g. show summary data for all customers or all orders.

In the past I have modelled these as persistent objects and allowed Hibernate to fetch all rows eagerly normally using inner joins. However this results in a large amount of redundant data being loaded and sometimes many queries.

Before using Hibernate I would have created a custom view and some simple sql which joined the tables and returned the few columns required.

Is there a standard approach to use Hibernate to return the sort of summary data required for the read-only lists described above?

Many thanks

Martin

Hi,
You have not mentioned any details of the problem. I suppose it is about querying only a few of the columns from a table plus being able to join 2 or more tables and fetching only the required columns.

I think you can create a custom query that returns set of columns from multiple tables. Check the manual Chapters 14, 16.

regards
Virimchi

I would say that a standard approach would be to do lazy loading of your objects, and implement the open session in view pattern. This will provide your applications with the data they need, but minimize queries to the database that are being used to load data that is not needed by the client.

Here's more information on the Open Session in View Design Principle.

http://www.hibernate.org/43.html

The custom query looks like the only way to achieve the performance gains.

Is it possible to make Hibernate populate custom pojos with the results from a custom query which accesses multiple tables

E.g. Can I make Hibernate return a list of UserSummary objects
custom query: select ... from user, address, order where ...;

Custom Pojo:
public class UserSummary {
String surname;
String city;
int numberOfOrders;
}

Thanks

Martin