Hi,
I have a seam-gen (Seam 2.1.1) generated project, when I use the a:actionparam tag instead of f:setPropertyListener it gives me the java.lang.NoClassDefFoundError: org/apache/commons/beanutils/PropertyUtils exception, so I moved the commons-beanutil.jar into the EAR lib and it gives me another error:

java.lang.StackOverflowError
 at java.lang.reflect.InvocationTargetException.<init>(InvocationTargetException.java:54)
 at sun.reflect.GeneratedMethodAccessor142.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.apache.commons.beanutils.PropertyUtilsBean.invokeMethod(PropertyUtilsBean.java:1773)
 at org.apache.commons.beanutils.PropertyUtilsBean.getSimpleProperty(PropertyUtilsBean.java:1132)
 at org.apache.commons.beanutils.PropertyUtilsBean.getNestedProperty(PropertyUtilsBean.java:686)
 at org.apache.commons.beanutils.PropertyUtilsBean.getProperty(PropertyUtilsBean.java:715)
 at org.apache.commons.beanutils.PropertyUtils.getProperty(PropertyUtils.java:290)
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:141)
 at org.ajax4jsf.javascript.ScriptUtils.toScript(ScriptUtils.java:86)
 ...

In particular I changed this code:

 <a:commandButton value="view">
 <f:setPropertyActionListener value="#{contact}"
 target="#{contactBean.selectedContact}"/>
 <f:setPropertyActionListener value="#{null}"
 target="#{contactBean.contactFieldsList}"/>
 <f:setPropertyActionListener value="#{null}"
 target="#{contactBean.contactAddressesList}"/>
 <f:setPropertyActionListener value="#{false}"
 target="#{contactBean.selectedContactEditing}"/>
 </a:commandButton>

into this:

 <a:commandButton value="view">
 <a:actionparam value="#{contact}"
 assignTo="#{contactBean.selectedContact}"/>
 <a:actionparam value="#{null}"
 assignTo="#{contactBean.contactFieldsList}"/>
 <a:actionparam value="#{null}"
 assignTo="#{contactBean.contactAddressesList}"/>
 <a:actionparam value="#{false}"
 assignTo="#{contactBean.selectedContactEditing}"/>
 </a:commandButton>

and I ran into the problem.

I think it's related to the issue: https://jira.jboss.org/jira/browse/RF-5004

Demetrio