JSF and expression language: Bind property only when it exists

Question

what is the best way to bind a datacolumn to a property that might or might not exist in the datasource?

This happens for example when you have a class hierarchy where some children might be of a subtype which has the property. The datasource contains various subclass types.

<DataColumn outputText="#{item.property}" />

always yields a PropertyNotFoundException when the property isn't present in one of the subclasses. I don't want to include the property in the base class because it shouldn't be there according to the business rules.

How would you solve this problem?

Answer 1

Without changing the classes, your best bet is to do kind of an instanceof in EL. You can do that by checking the (simple) classname as obtained by Object#getClass() and then Class#getName() or Class#getSimpleName() in EL.

Assuming that the class with the property has the full qualified name com.example.SubItem, here's an example:

<h:outputText value="#{item.property}" rendered="#{item.class.name == 'com.example.SubItem'}" />

or

<h:outputText value="#{item.property}" rendered="#{item.class.simpleName == 'SubItem'}" />