Managing beans based on URL query parameters

Question

I was just reading this thread with interest, but it didn't come to the conclusion that I need.
http://forum.java.sun.com/thread.jsp?forum=427&thread=441432
In that thread, there were two screens: a table of links to employees and an "edit employee" page. The solution was to use the command_action on the list create an "employee data" bean, which could then be edited on the "edit employee" page.
My problem is that I need to create some session beans based on query parameters in the URL. Using the example above, I'd have something like: http://localhost/app/editEmployee?empNo=38
Why? Because the user can bookmark the edit employee page, have two
browser windows open (which would require two seperate employee data beans), etc... and we need to handle that. It looks like
that means I can't use the solution in the above thread.
My current thought is to create a managed-bean with request scope and have it create the EmployeeData bean.
Another idea is to somehow initialize the bean with managed-properties
<managed-bean>
    <managed-bean-name>EmpBean</managed-bean-name>
    <managed-bean-class>com.mycompany.EmpBean</managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
    <managed-property>
        <property-name>employeeID</property-name>
        <value-ref>queryParamBean</value-ref>
    </managed-property>
</managed-bean>
<!--
  just returns FacesContext.getCurrentInstance().getServletRequest().getParameter("id")
-->
<managed-bean>
    <managed-bean-name>queryParamBean</managed-bean-name>
    <managed-bean-class>com.mycompany.QueryParamBean</managed-bean-class>
    <managed-bean-scope>none</managed-bean-scope>but that seems kinda hacky. Any other ideas?

Answer 1

Excellent, using requestScope gets rid of the queryParamBean hack from my first post. For some reason I thought value-ref evaluatations only resolved against stuff the VariableResolver can see. That's not the case. Thanks.
Unfortunately, this bean really wants to be cached on the session, not the request. I suppose it would be possible to have EmpBean delegate to a bean which is actually cached on the session, but that feels like a hack too (and is a lot of glue code).
So, I think I'm back to the factory, which can handle creating the bean from the query params, caching it, and putting it on the servlet request. I also got a visit from Captain Obvious and realized that the factory could just be a scriplet.
<% BeanCreator.createBean("com.company.EmpBean", request.getParameter("id")); %>which also isn't great, but is perhaps easier to understand than the BeanCreator from above. I looked into using EL Functions in the variable resolver for the factory, but it doesn't look like that's possible. It's probably possible to extend VariableResolver to add factory methods for managed-beans, which might be the cleanest solution. I'm thinking something like
<managed-bean>
  <managed-bean-name>Emp</managed-bean-name>
  <managed-bean-factory>
     <factory-name>com.company.BeanFactory.getBean</factory-name>
     <bean-class>com.company.EmpBean</bean-class>
     <arg-value-ref>sessionScope.id</arg-value-ref>
  </managed-bean-factory>But for now, the current two hacks are:
#1: to create a URL use plain html <href>.
#2: use a factory method (varying implementions) to create the bean, cache it, and put it on the servlet request