sorting main report and sub-report with xml datasource

[visert]

Hi

main report "MR"... and its sub report "SR".

Data into XML are in 1:n relationship cardinality between MR -> SR records (mr01 -> sr01, mr01->sr02... ecc ecc).

Data source is a JRXMLdatasource ( a XML file).

Without sorting, the report is printed correctly, But I need to sort both MR and SR records.

I pass the datasource from MR to SR with tipical sentence:

"((net.sf.jasperreports.engine.data.JRXmlDataSource)$P{REPORT_DATA_SOURCE}).subDataSource("field")

If I try to sort  a field into MR:  the JRXMLDataSource "became" ListOfArrayDataSource and so I need to change the sentence into

((net.sf.jasperreports.engine.data.ListOfArrayDataSource)$P{REPORT_DATA_SOURCE})

 otherwise I ("correctly") receive a cast exception

ClassCastException ListOfArrayDataSource cannot be cast JRXmlDataSource.

Well... no compile error, no runtime error, but SR is empty. I think because to sort MR the engine has "finished" records?

It's possibile inside SR command the restart of scanning of record? If yes... will be correctly assigned to MR records?

Thank you to all for help.

bye

best regards to all!