The pages.xml file assumes that for a given view-id, all responses/updates
are handled identically. That isn't necessarily a good idea as it means that
the
action is the same in all cases and that violates separation of concerns. In
specific, the example in the tutorial:
| <page view-id="/calculator.jsp" action="#{calculator.calculate}">
| <param name="x" value="#{calculator.lhs}"/>
| <param name="y" value="#{calculator.rhs}"/>
| <param name="op" converter="#{operatorConverter}"
value="#{calculator.op}"/>
| </page>
|
implies that calculator.calculate knows about EVERY op possible. In this
example, it isn't possible to add a new operation without modifying
calculator.calculate. Sometimes that is a good idea if there are a very few
operations available, but if there are lots of operations, then
calculator.calculate needs to have some sort of registration mechanism for new
operations - however, consider the operation ?: that takes x,y,z. This
operation won't work because the parsing doesn't work correctly. Or consider
the hex conversion operation - again, the value is probably a double or integer
or some such thing, and the parsing doesn't work for that either.
It would be helpful to have something like:
| <pages>
| <page view-id="/calculator.jsp" action="#{calculator.calculate}">
| <param name="x" value="#{calculator.lhs}"/>
| <param name="y" value="#{calculator.rhs}"/>
| <param name="op" converter="#{operatorConverter}"
value="#{calculator.op}"/>
| <view-modifier value="#{calculator.op}" />
| </page>
| <page view-id="/calculator.jsp" view-modifier="+"
action="#{calculator.add}" />
| <page view-id="/calculator.jsp" view-modifier="?:">
| <param name="z" value="#{trivalued.z}" />
| </page>
| </pages>
|
Note that this works fairly well with RESTful services - the post can be done
to the same URL, but different actions can go through different operations, and
then still render the same overall page.
It also works well if you want to add another outcome variant - just add a view
modifier and add a new outcome.
View the original post :
http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4049427#4049427
Reply to the post :
http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4049427
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