Chip Wilson wrote:
>There is an even more compelling reason to place the creation/retrieval of
>collections of summary objects in a session bean rather than an entity
bean.
>Summary objects are part of the application model layer of the
architecture,
>not the domain layer. Entity beans are appropriately placed in the domain
>layer, as coarse-grained facades to the domain model. Session beans, on
the
>other hand, are appropriately placed in the application model layer, as
>use-case controllers and the implementers of the application's system
>operations. The creation of summary objects, being a responsibility of
the
>application model layer, is most appropriately placed in a session bean.
Chip,
We agree that EJBs are not fine-grained domain objects. But you are also
trying to stop them being fully fledged components.
1. Components are about encapsulation of data and as much function as
possible that operates on that data to enable reuse at runtime.
2. Components are about security/integrity. A Component CONTROLS the
data it encapsulates. Other components (and clients) should not
have direct access to the database that the component operates on.
Insisting that EBs are "coarse-grained facades to the domain model" is an
arbitrary and unnecessary restriction on enabling them to take on the role
of components.
Ian McCallion
CICS Business Unit
IBM Hursley
[EMAIL PROTECTED]
Tel: ++44-1962-818065
Fax: ++44-1962-818069
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