How to draw vertical line in iReport

The best solution to this is to add an additional parameter like $P{IsOnServer}. Set the default value to true. For your subreport expression use this:

$P{IsOnServer} ? "repo:mySubReport.jrxml" : "/local/path/to/mySubReport.jasper"

When you run the report in iReport, you'll be prompted for the value of IsOnServer. Make it false; the subreport expression will resolve to your local file. On the server, don't define an input control. The users will never be prompted for that parameter (they won't even know it exists), and it will result to the desired 'repo' syntax.

An even better solution would of course be for iReport to handle this automatically... but for now you need to do something like this.

I think that in your second example B is actually null but perhaps your text field has the 'Blank When Null' property set. I was able to reproduce your results except for the blank for B.

The real issue is that you can't add or subtract with a null value. JasperReports will just print null. You have to add some logic to provide a default value if one of the variables in the expression is null. For example

$F{MAIN_REPORT_FIELD} - ($V{SUB_RESULT} == null ? 0 : $V{SUB_RESULT})

Unfortunately, this is broken for reports that use Groovy for expressions in JasperReports 4.0.2 (Case 0005138) and will always return null.

You have a few options:

1. You could upgrade to JasperReports/iReport 4.1.1 which resolves this issue.

2. You could switch to using Java for expressions.

   Depending on your report this will either be painless or it will be a chore. Any fields that don't have the correct Expression Class will have to be fixed up and you'll probably have to be more explicit in any expression that performs operations on non primitive/wrapper types.