Managed Property from one bean to another

Question

Can someone of you explain me, why the first code works and the other one doesn't?

Working:

<h:commandButton value="#{settingsBean.tmp}" action="editverteilerliste">
    <f:setPropertyActionListener target="#{settingsEditVerteilerlisteBean.aktuelleVerteilerliste}" value="#{settingsBean.tmp}" />
</h:commandButton>

Not Working:

<p:commandLink action="editverteilerliste">
    <f:param name="aktuelleVerteilerliste" value="#{settingsBean.tmp}" />
    <h:outputText value="asdf"/>
</p:commandLink>

settingsBean.tmp is a instance of Verteilerliste

Action editverteilerliste leads to another page which is using the settingsEditVerteilerlisteBean:

@ManagedBean
@RequestScoped
public class settingsEditVerteilerlisteBean implements Serializable {

  private Logger logger = Logger.getLogger(settingsEditVerteilerlisteBean.class);

  public settingsEditVerteilerlisteBean() {
  }

  @PostConstruct
  public void init() {
    logger.info("Postconstructor invoked!");
  }

  @ManagedProperty(value = "#{aktuelleVerteilerliste}")
  private Verteilerliste aktuelleVerteilerliste;

  [Getter and Setter...]
}

The second page:

<h:body>
    <ui:composition template="../template/mainlayout.xhtml">
        <ui:define name="content">
            <h3>Verteilerliste <h:outputText value="#{settingsEditVerteilerlisteBean.aktuelleVerteilerliste.name}"/></h3>
        </ui:define>
    </ui:composition>
</h:body>

I know I just could use the working one but I want to understand why second one doens't work!

Answer 1

The second one doesn't work because your managed property binding is resolved to null, as there is most possibly no element for aktuelleVerteilerliste key in any of the JSF-scoped maps.

To make the second one work you need to tell JSF to look within parameters of a given request, i.e. change to @ManagedProperty(value = "#{param['aktuelleVerteilerliste']}").

To make the distinction more clear, <f:setPropertyActionListener> simply equates target object to value in invoke application phase of JSF lifecycle while the latter approach simply adds a particular parameter to a JSF component, which is command component in your case, and command component parameters can be accessed via EL object param that is a map of current request parameters.

---

That said, your usage of command links is considered to be a bad practice. They are used to invoke some server-side logic when the form is submitted to perform some business job. In your case you are using them to perform plain navigation. For this you'd be better off using <h:link> components to create simple a elements. This way, if you attach a parameter you'll end up with a query parameter like editverteilerliste?aktuelleVerteilerliste=something that you can get in the view via <f:viewParam>. That way you'll end up with bookmarkable URLs and clear navigation in your application.