Reusing a datasorce in mutiple subreports

[tdiffenbach]

I wish to reuse, in its entirety, a datasource in multiple subreports. The SQL is relatively expensive, so I'd like to avoid generating it multiple times.

 

It appears that this will require

 

a. Using a JRRewindableDataSource in the main report, and

b. calling moveFirst() on that datasource in each subreport.

 

How can I do this? I don't see a way to specify the type of the main report's datasource type, and I'm not clear how to ensure the call moveFirst() on the datasource in the subreport happens prior to the subreport accessing the datasource's data.

 

Thanks.

[lucianc]

a. Reports that embed SQL queries use JRResultSetDataSource as data source, and this type is not (currenlty) rewindable. If you think rewindable SQL data sources would be useful, please post a feature request for this.

 

You can also achieve this outside JR by writing a custom SQL query executer that uses TYPE_SCROLL_INSENSITIVE statements to create rewindable result set data sources.

 

If the result set is small, an alternative to this is to execute the result set before starting to fill the report, record all the data returned by the result set in an in-memory structure and then use the in-memory data as data source for the subreports.

 

b. You could, for instance, use the auto rewindable data source wrapper posted here.

 

HTH,

Lucian