[jboss-user] [JBoss Seam] - Polimorphism problem :(

[przemjaskier]

 ** Problem: I cannot customize content of a template, depending on a type of returned hibernate @Entity. 

** Environment: MyFaces 1.1.4, Facelets 1.1.12, Seam 1.1.6, Hibernate 3.2.1. 

** Situation: 
I have three Hibernate entities: 
1. Item - annotated with @Inheritance(strategy=InheritanceType.SINGLE_TABLE), @DiscriminatorColumn, @DiscriminatorValue, @Entity 
public void getProperty(); 
isExtendedFlagSet(); //returning true only when this is instance of 
//ExtendedItem below (I need such flags in 
//general) 
2. ExtendedItem extends Item - annotated with @DiscriminatorValue, @Entity 
public void getExtendedProperty(); 
3. ItemHolder - annotated with @Entity 
Item getItem(); 

And an EVENT scope backer: 
currentItemProvider getting ItemHolder proxies/instances from Hibernate. 

And two jsf+facelets templates, which I want to render different in case when ItemHolder.getItem() 
returns instance if ExtendedItem than when it returns instance of Item. 

** My (not working completely) solution: 

Using custom, render-time-if component, which renders children when "currentItemProvider.itemholder.item.extendedFlagSet" is true, 
enable fragment of page: 

<h:outputText value="#{currentItemProvider.itemholder.item.property}"/> 
<mycomp:renderTimeIf condition="#{currentItemProvider.itemholder.item.extendedFlagSet}"> 


<h:outputText value="#{currentItemProvider.itemholder.item.extendedProperty}"/> 

</mycomp:renderTimeIf> 

1. WORKS OK, when placed in a render-time loop of ui:repeat. Different item appear 
on a page rendered according to their isExtendedFlagSet value 

2. But DOESN'T work when put in compile-time ui:decorate or direct in a template. I get: 

SEVERE: Error Rendering View[/itemDetails.xhtml] 
javax.faces.el.PropertyNotFoundException: /WEB-INF/templates/itemtemplate.xhtml @18,132 value="#{currentItemProvider.itemholder.item.extendedProperty}": 
Bean: package.Item$$EnhancerByCGLIB$$b215fa4e, property: extendedProperty 
at com.sun.facelets.el.LegacyValueBinding.getValue(LegacyValueBinding.java:58) 
at javax.faces.component.UIOutput.getValue(UIOutput.java:77) 
at org.apache.myfaces.shared_impl.renderkit.RendererUtils.getStringValue(RendererUtils.java:217) 
at org.apache.myfaces.shared_impl.renderkit.html.HtmlTextRendererBase.renderOutput(HtmlTextRendererBase.java:69) 
at org.apache.myfaces.shared_impl.renderkit.html.HtmlTextRendererBase.encodeEnd(HtmlTextRendererBase.java:57) 
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:536) 


** Question: how to deal with such instance-dependent customization? I have a huge, complex domain (above is only a simplified illustration) 
and would gladly stay with this consistent isFlasSet() approach, but if it should be done in a different way, please suggest. 

Regards, 
Przemek

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