Suppose,
customerBean has a one-to-many relationship with accountBean
accountBean has a one-to-one relationship with addressBean
customerBean has a one-to-one relationship with phoneBean
then what about
<read-ahead>
<!-- read customers -->
<strategy>on-load</strategy>
<page-size>100</page-size>
<eager-load-group>customer_group</eager-load-group>
<!-- read customer's accounts -->
<read-ahead>
<cmr-field>accounts</cmr-field>
<strategy>on-load</strategry>
<page-size>10</page-size>
<eager-load-group>account_group</eager-load-group>
<!-- read account's address -->
<read-ahead>
<cmr-field>address</cmr-field>
<strategy>on-find</strategry>
<eager-load-group>address_group</eager-load-group>
</read-ahead>
</read-ahead>
<!-- read customer's phone -->
<read-ahead>
<cmr-field>phone</cmr-field>
<strategy>on-find</strategry>
<eager-load-group>phone_group</eager-load-group>
</read-ahead>
</read-ahead>
Note, sql statements for these queries could return duplicates.
alex
Wednesday, October 23, 2002, 5:23:30 AM, you wrote:
DS> I totally agree and this is already planned for JBoss 4.0. The real
DS> problem is not the code to do the loading but figuring out a simple xml
DS> structure to define the loading.
DS> -dain
DS> Emerson Cargnin - SICREDI Servi�os wrote:
>> I have a suggestion regarding to CMP : why not create a configuration to
>> a find method to allow the container to load the relationships of a bean?
>>
>> This could be useful in the cases you have to read all the beans(or a
>> good amount of then) and all (or almost all) relationships of them. eg :
>> in a report you will have a sql to finding the pk's, one (at least) to
>> load the bean data and one sql to each relation you have to report (for
>> each bean).
>>
>> I think that one of the worse problem with CMP is that : database
>> overhead. CMP generates too much sql commands that in some cases could
>> be handled by fewer (if not one) sql commands. The DBA's in my company
>> didn't like very much the trace they saw in the database for a very
>> simple app.
--
Best regards,
Alex Loubyansky
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