Jasper Report Server - Hyperlinks to Subreports!

Dearest potentially non-existent readers,

My first post here will be a small note on how to configure Jasper Reports running on Jasper Report Server to contain hyperlinks to subreports.  This may seem simple and intuitive but it really isn't.  I've witnessed a lot of confusion and red-herring chasing on the net about this so I figured it's worth writing a rough set of instructions for how to do this.  Here it is:

Sub Report

1. In Jasper Reports Server, Create a separate Jasper Report for the subreport of choice.
2. Create an Input Control that matches every parameter you expect to be passed to the subreport through the hyperlink.

Parent Report

1. Right click on a text field of choice and select 'Hyperlink'.
2. Set 'Hyperlink target' to "Self".
3. Set 'Hyperlink type' to "ReportExecution".
4. Click on 'Link parameters'. 
1. Create a report parameter called '_report'. 
2. Set its expression to a repository location using the "repo:" syntax.  This part is strange.. it seems the url you provide here should be relative to two parent directories above the current report... e.g. for parent report  at "/organizations/organization1/reports/parent", subreport at "/organizations/organization1/reports/subreport", set '_report' parameter to "repo:/reports/subreport" (with quotes).
5. Set all the report parameters required.  Ensure that the names of these parameters match the parameter names of the Input Controls defined for the sub report.
6. Upload the report to Jasper Server

The way I trial and error'd my way through figuring out what to set for the '_report' parameter was to view the hyperlink created in the parent report (using firebug) and copy its value into a text file, then open the subreport by itself and copy its url into a text file.  Observing the &reportUnit parameter:

 URL:  
  &reportUnit=%2Forganizations%2Forganization1%2Freports%2Fsubreport  
 Hyperlink:  
  &reportUnit=repo%3A%2Forganizations%2Forganization1%2Freports%2Fsubreport  

.. it became clear that tweaking the "_report" parameter until the 'reportUnit' parameters were identical (save for the "repo:" prefix in the hyperlink) made for a working hyperlink.
For your reference, the error you get when clicking on a hyperlink that isn't correctly set is the following:

 java.lang.NullPointerException at   
 com.jaspersoft.jasperserver.war.action.ResourceTypeMappingAction.doPreExecute(ResourceTypeMappingAction  
 .java:53) at org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:186) at   
 org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51) at   
 org.springframework.webflow.action.EvaluateAction.doExecute(EvaluateAction.java:79) at   
 org.springframework.webflow.action.AbstractAction.execute(AbstractAction.java:188) at   
 org.springframework.webflow.execution.AnnotatedAction.execute(AnnotatedAction.java:145) at   
 org.springframework.webflow.execution.ActionExecutor.execute(ActionExecutor.java:51) at   
 org.springframework.webflow.engine.ActionState.doEnter(ActionState.java:101) at   
 org.springframework.webflow.engine.State.enter(State.java:194) at   
 org.springframework.webflow.engine.Flow.start(Flow.java:535) at   
 org.springframework.webflow.engine.impl.FlowExecutionImpl.start(FlowExecutionImpl.java:364) at   
 org.springframework.webflow.engine.impl.RequestControlContextImpl.start(RequestControlContextImpl.java:234)   
 at org.springframework.webflow.engine.SubflowState.doEnter(SubflowState.java:101) at   
 org.springframework.webflow.engine.State.enter(State.java:194) at   

Also, it's worth noting that it isn't possible to pass parameters of any type other than those defined by the Input Controls in the subreport :(.  Perhaps there's a way around this?  I dunno...


Hope this helps someone!