[jboss-user] [JBoss Seam] - Let Seam instantiate a second component?

Newlukai do-not-reply at jboss.com
Thu May 31 04:50:15 EDT 2007


I'm wondering if and how it is possible to let Seam instantiate a component B from a component A.

I have a component A - call it Manager - which is supposed to receive some data to create and persist a new entity. Therefore the Manager outjects a "blank entity" which is later injected with the data from the user. Some values are preset using a @Factory method in the Manager.

On the page the user sees to input his data, there is a drop-down menu, realised with s:selectItems which doesn't use the noSelectionLabel. Depending on the selected value some other values are set by the Manager. The drop-down menu gets its values from a component B - call it Selector. The current selected value is bijected in a third component - call it selectedValue - so that the Manager can adapt some values depending on the selectedValue.
Since there's no noSelectionLabel, i. e. the user has to choose a value, the @Create method of this Selector queries the database for some values and outjects the first one as selectedValue.

That works pretty good, but there's only one last thing to do: The first time the page is displayed, the @Factory method in Manager is invoked. And as you might guess the selectedValue is null. That's because the Selector is instantiated after the instantiation of the Manager since it occurs later on the page. But actually I want to preset some values depending on the selectedValue outjected by the @Create method of the Selector.

Is there a way to tell Seam to instantiate the Selector before the @Factory method of the Manager is invoked? One way would be to place a dummy call from the JSF page before the Manager is called. But that isn't a good design I think. Another way would be the usage of @Startup(depends). But actually I don't want to have both components instantiated before they are needed. Is there another way?

Thanks in advance

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