iReport/JasperReports Server: Subreport return value null - jasper-reports

Question

I have the following problem with iReport / JasperReports server.
I'm using a main reports with two subreports returning a calculated price, the type of the subreport variable and the local variable is BigDecimal.
If the return value from a subreport is null (no rows found) then the assigned local variable in the main report is always null. But I want to have "0.00" because I want to calculate a sum.
The construct (return_variable == null ? new BigDecimal(0) : return_variable) doesn't help as well as to set the local variable to a default value new BigDecimal(0). I always get null instead of the wanted value "0.00" ;-(
I've tested with version 3.7.6 until 4.4. of iReport, nothing helps.
Does anybody have a hint for me? Thank you in advance.

Answer 1

I've had the same problem, except I tried to use the return value of the subreport as a parameter of another subreport. I succeeded in getting the result I wanted by using a scriptlet in the second subreport.
I proceeded this way :
-in subreport 2, I have my parameter p (Float), its value being the return value of subreport 1
-in subreport 2, I have a variable v (Float), initialized with p
-in my scriptlet (in the method beforeDetailEval(), I test my variable v : if it is null, I assign the value new Float("0.0")
I works ok.
The limitation with this is if you want to use the return value of your subreport directly in your main report. I tried doing that, but never succeeded.
Hope this will help someone some day.
Cecilka

Answer 2

Yahoo! By the Grace of GOD, I found a great answer to my own question. Posting it as it may help someone in future.
1) I changed my Simple SQL Query with a MySQL stored procedure as.
My Stored Procedure as
BEGIN
SET #p = 0;
SET #n = 0;
SET #m = '00';
SELECT x.*, y.* FROM
(select #n:=#n+1 as "ID", #m:=acc as "Account" from tbl_reports) x
right JOIN
(SELECT if(#m='00',0,#p:=#p+1) as "IDU") y
ON y.IDU = x.ID;
END
In IReport, I declared my variable as
$F{IDU}>0?$F{Amount}:0
In this way, it now shows 0.00 instead of null.