redirect-action parameters

[Pascal Lalonde]

Based on this sample from the web site documentation:
<!--
    The redirect-action url generated will be :
    /genReport/generateReport.action?reportType=pie&width=100&height=100
    -->
    <action name="gatherReportInfo" class="...">
       <result name="showReportResult" type="redirect-action">
        <param name="actionName">generateReport</param>
          <param name="namespace">/genReport</param>
          <param name="reportType">pie</param>
          <param name="width">100</param>
          <param name="height">100</param>
       </result>
    </action>


How can I add dynamic parameters ?
Here, values are fixed but what if I want to set a dynamic value from the 
action data ?

Based on this

When setting:
<param name="testKey">abc</param>

I'm having the following error:
WARNING: Caught OgnlException while setting property 'testKey' on type 
'org.apache.struts2.dispatcher.ServletActionRedirectResult'.
ognl.NoSuchPropertyException: 
org.apache.struts2.dispatcher.ServletActionRedirectResult.testKey at 
ognl.ObjectPropertyAccessor.setProperty(ObjectPropertyAccessor.java:133)

What is happening here ?

Thanks