Philip Aston wrote:
> In any transaction, including distributed ones, you should see the
> committed state plus the effects of changes made earlier within the
> same transaction. Outside the transaction you should only see the
> committed state.
Agree 100%. But only if we can agree to exclude the examples Chip Wilson pointed
out where two beans of different classes instantiate the same database data. If
we exclude these situations, we are saying that for the duration of a
transaction, a bean's state is pure WORKING STORAGE which seems emminently
reasonable to me. If we insist on including them then:
1. A change in state of bean A (say) could cause a change in state of bean B
without a method of bean B being called - thus violating the encapsulation rule.
2. The implementation if this would involve loading and storing the entire bean
state for every method call thus killing performance.
3. Whenever bean A changes state any validation of the data already performed by
bean B would be nullified, so making it pointless to validate the data.
In other words encompassing Chip's examples within your consistency rule
violates encapsulation, performs like a dog and is useless to the developer.
(Flogging ended. Is the horse dead yet;-)
> The behaviour clearly requires a lot of ejbStore/ejbLoads to ensure
> correct behaviour and consequently efficient implementations need very
> tight intergration between the EJB server and database. There are
> clear potential efficiency speed-ups if, for example, a container
> knows it has exclusive access to a database.
Disagree. Taking away Chip's examples, there is no need to do lots of
ejbStore/ejbLoads. Correct behaviour is achieved if finders edit (i.e. add and
delete beans from) their results based on the beans that are already involved in
the transaction.
Ian McCallion
CICS Business Unit
IBM Hursley
[EMAIL PROTECTED]
Tel: ++44-1962-818065
Fax: ++44-1962-818069
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