CMP2.0 and query data mapping?!?

[davout]

I would be grateful if somebody could help me out with an idiot level description of what CMP2.0 includes for abstracting the definition of large scale data queries.

This question carries over from a question posted in the 'Beginners' forum (http://www.jboss.org/modules/bb/index.html?module=bb&op=viewtopic&t=forums/ as much that CMP looks after entity CRUD actions by having a XML based mapping to underlying data sources, there doesn't seem to be the same abstraction layer for retrieving lists of entity related properties, like...

select customerID, customerName from Customer

Somebodsy said that CMP2.0 could handle this. True?

If so does JBoss handle this now?

[aloubyansky]

Do you mean load-groups and read-ahead? Check Start Guide at sf.net.

[davout]

Here's a quote from my original thread/question...

---oOo---

Take a situation where I want to run a query against a customer database. Something like....

select customerID, customerName from customers

It does'nt make any sense to retrieve the entire Customer object. Also what happens if the customer object is a composite of things like...

Customer
|--- Customer Address Info
|--- Customer Order Info
|--- Customer Contacts

A finder would bring back huge amounts of data that simply isn't relevant.

I was sort of expecting EJB to include some of logical entity to data source mapping structure for all aspexcts of the data model - not just entity CRUD.

The few books I've read suggest using a DAO pattern for masking JDBC calls. Again this seems detached from the container based persistence.

[aloubyansky]

You need to learn load-groups and read-ahead. It allows to setup what fields(columns) will be loaded and what raws will be read ahead.
Have you looked at Start Guide on sf.net, Dain's book?

[davout]

I'm a newbie to this area...

Where do I find both of these?

[aloubyansky]

http://www.jboss.org/docs/