Designing totals wit BC4J

Question

How would you design this:
You have a table REV of revenues per day (date PER and number REV). There may be more than one row per day (let's say one for each order). You have to make BC4J that give you access to the single rows for retrieval and update. So far no difficulty (default EO and VO will do). But you have to keep track of the daily and monthly sums of the revenues, displaying them and updating them as the user adds rows to the table REV and makes changes to existing rows.
So I may make two expert mode VOs that retrieves the sums (one for the monthly and one for the daily sums). But where to keep track of the uncommited revenues ? A VO can not subscribe events, can it ? And I think it is not possible to make a EO that is based exclusively on calculated attributes (this had to be the case since there is no DB-Object corresponding to the sums, and I am not willing to make a DB-View for this purpose, as I would certainly get into performance issues with the inevitable group-by).
I had to handcraft two hashtables for the sums of the uncommited changes against the months and days, respectively, and put them into the EO of REV.
Or I put the calculations into the VO of REV, present it with the means of client methods (or client row methods?), and back it up again with hashtables to cache the values. But how to catch the uncommited changes ?
Pascal Glauser

Answer 1

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by JDev Team:
I guess you would want to update the values of 'dailyTotal' and 'monthlyTotal' as the user add/updates individual rows of data (i.e revenue for each day)
You could add two transient/caluclated attributes at the EO level
1) dailyTotal
2) monthlyTotal
these two attributes are not persistent and not database columns
The EO would also have other database colums such as 'Revenue'
In the setRevenue() method (which gets invoked whenever the user manipulates the row) you could recaluclate the transient attributes.
For ex:
public void setReveunu(Number value) {
Number dayrev = getdailyTotal();
dayrev.add(value);
setdailyTotal(dayrev);
this would add the new value updated in the revenue column of a day to the dailyTotal.
you could add some more logic into the setter of the revenue to suit your needs, similarly you could also do for the monthlyTotal.
You would want to keep the Transient attributes at the EO if you want them to seen across different VO's or if the Transient attribute need to be seen by a single VO then you could maintain it the VO level.
raghu<HR></BLOCKQUOTE>
Dear JDev Team
Thank you very much for your answer.
I know about the possibilities of transient attributes at the EO level. There will indeed be some more logic as the frequency of the sums is not the same like the frequence of the entity itself.
I noticed that there can be calculated attributes at the VO, too. The missing link is, how will the VO be informed, if an attribute of one of its rows is changed. A VO cannot subscribe events, can it ?
Pascal Glauser
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