JSF: what is the "correct" way of doing this? - jsf

Question

I've been using JSF for a while but there's something that has always confused me. Hopefully someone can help.
Simple example, there's a page that shows a table of "Person"s and when you click on the "Person" name, it takes you to a page to view the details of the "Person".
Typically, I implement a personSearch.jsf page like this:
<h:dataTable value="#{personHandler.persons}" var="person">
<h:column>
<h:commandLink action="#{personHandler.show( person.id )}" >
<h:outputText value="#{person.name}" />
</h:commandLink>
</h:column>
</h:dataTable>
And I implement a personView.jsf page like this:
<h:panelGrid columns="2">
<h:outputText value="Person ID:" />
<h:outputText value="#{personHandler.selectedPerson.id}" />
<h:outputText value="Person Name:" />
<h:outputText value="#{personHandler.selectedPerson.name}" />
</h:panelGrid>
PersonHandler.show(Integer personId) sets personHandler.selectedPerson and then redirects to the personView page.
This all works fine when PersonHandler is a session bean. But I prefer it to be a request scoped bean because the user may have several windows open and I don't want there to be only one selected person per session.
So my question is, what's the "correct" way to do this JSF? I was once able to get what I wanted using a4j:keepAlive on the personHandler, but that always felt like a kludge. Again, this is something I've never understood about JSF.
Any help is greatly appreciated!
rob

Answer 1

If the view is supposed to be bookmarkable, pass the person ID as a GET request parameter instead of a POST request "parameter".
<h:outputLink value="viewperson.xhtml">
<f:param name="id" value="#{person.id}" />
</h:outputLink>
This way you can use two #RequestScoped beans, one for the list and one for the view. You can preload the selected person as follows:
#ManagedProperty(value="#{param.id}")
private Long id;
#PostConstruct
public void init() {
selectedPerson = personDAO.find(id);
}
If it is not supposed to be bookmarkable, then just create a single view which renders the view state conditionally.
<ui:fragment rendered="#{!personHandler.viewMode}">
<h:form>
<h:dataTable value="#{personHandler.persons}" var="person">
<h:column>
<h:commandLink value="#{person.name}" action="#{personHandler.show(person)}" />
</h:column>
</h:dataTable>
</h:form>
</ui:fragment>
<ui:fragment rendered="#{personHandler.viewMode}">
<h:form>
...
<h:commandLink value="Go back" action="#{personHandler.back}" />
</h:form>
</ui:fragment>
(You can if necessary split out the content of the both framgents to another Facelet files which you include by <ui:include>)
This way you can use a single #ViewScoped bean with action methods returning void or null.
public void show(Person selectedPerson) {
this.selectedPerson = selectedPerson;
}
public void back() {
selectedPerson = null;
}
public boolean isViewMode() {
return selectedPerson != null;
}
You can even wrap the whole view in some
<h:panelGroup id="container">
and nest the following in both command links to let Ajax magic do the work
<f:ajax execute="#form" render=":container" />