That it works in JSP is meaningless--the two mechanisms are nothing
alike. The error message describes exactly what the problem is; you're
passing a list, not something that JR can use.
Tragically, I don't actually remember what I did to fix this, although
I thought I had changed the plugin to handle that. Perhaps I never
checked it in, which would be too bad, because I no longer have access
to that code :(
Dave
On Wed, Feb 16, 2011 at 12:11 PM, Aaron Brown <aa...@thebrownproject.com> wrote:
> I'm learning how to use Jasper reports, in this case as a result from
> a Struts2 (2.1.8) web app. I'm sending a List (ArrayList) of objects
> to a report and when the case is that simple, I have things working
> just fine.
>
> Next, I need to report a hierarchy of data like this example:
> List<Parent> parents;
>
> Parent:
> String name;
> List<Child> children;
>
> Child:
> String name;
>
> So I want to send the list of Parent objects to report A. This report
> includes a subreport, B, which should iterate over the list of Child
> objects for each Parent. Like:
> for (Parent p : parents) {
> for (Child c : p.children) {
> // report
> }
> }
>
> My problem is that my report, which compiles cleanly, cannot be
> "filled" by the Struts action. I instead get a stack trace about not
> being able to evaluate the expression $F{children}, and the end of the
> stack trace says:
>
> Caused by: java.lang.ClassCastException:
> org.apache.struts2.views.jasperreports.ValueStackDataSource
> incompatible with java.util.List
>
> I use hibernate and lazy loading on the back end, so I added a loop to
> pre-fetch and initialize all the "children" lists for each parent,
> just to make sure it wasn't an issue with lazy loading and sessions
> and such. The problem still occurs.
>
> I'm also making sure each "children" ArrayList is either full of data
> or initialized as an empty ArrayList, so there should not be any Null
> references.
>
> It appears from the stack trace error that Struts is not allowing
> Jasper to access the nested property of the Parent object. I'm doing
> the same kind of operation in a dozen places in .jsps, so I know my
> object model is solid.
>
> Does anyone have experience with this kind of Struts 2 reporting in
> Jasper who could lend me a hand learning how to do this?
>
> thanks,
> - Aaron
>
> --
> Aaron Brown : aa...@thebrownproject.com
>
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