Execute a method before a page is displayed?

Question

I love JSF, but I have continuously run in to a wall trying to figure out how to execute code before a page is displayed. Is there some Listener/Binding mechanism that I could tap into that would be called before Render Response?
A Phase Listener is too general, I don't want something that walks the tree for every request.
Action/ValueChange Listeners are only called after a user takes an action.
Putting calls (for example DAO) in getter methods works in some circumstances, but is fragile and is insufficient when you need to populate multiple fields on a bean but only want one (DB) call. (You can put it on the first one that will be called, but this destroys reusability).
The only sucessful strategy I have found is having an init() that returns boolean and calling it from the first <h:outputText> on the screen's render field. This is obviously a painful hack.
This is a general question, but my current scenario is a single DB lookup needs to get a list of beans before a page is displayed. (users can link directly to the page). Once the lookup is complete the list of beans is displayed in 3 seperate data tables with 3 seperate action bindings. So it doesnt really make sense to do the db lookup in one get method that populates the 2 other lists, though it would be a functional approach.
Any thoughts?

Answer 1

I love JSF, but I have continuously run in to a wall
trying to figure out how to execute code before a
page is displayed. Is there some Listener/Binding
mechanism that I could tap into that would be called
before Render Response? In vanilla JSF? No.
In JSFTemplating: yes.
It provides an "initPage" event which is invoked every time a page is "initialized" (which may be a long time before it is displayed). It also provides an <event> component which includes a "beforeEncode" event which is invoked during renderring.
A Phase Listener is too general, I don't want
something that walks the tree for every request. I agree.
Action/ValueChange Listeners are only called after a
user takes an action. Yep.
Putting calls (for example DAO) in getter methods
works in some circumstances, but is fragile and is
insufficient when you need to populate multiple
fields on a bean but only want one (DB) call. (You
can put it on the first one that will be called, but
this destroys reusability).Exactly.
The only sucessful strategy I have found is having an
init() that returns boolean and calling it from the
first <h:outputText> on the screen's render field.
This is obviously a painful hack.Yep.
This is a general question, but my current scenario
is a single DB lookup needs to get a list of beans
before a page is displayed. (users can link directly
to the page). Once the lookup is complete the list of
beans is displayed in 3 seperate data tables with 3
seperate action bindings. So it doesnt really make
sense to do the db lookup in one get method that
populates the 2 other lists, though it would be a
functional approach.The "events" I mentioned above for JSFTemplating allow any # of parameterized "handlers" to be invoked. "handlers" are more reusable than #{} method bindings due to their support for multiple inputs and outputs. You also do not have to do any faces-config.xml file configuration, they are defined via Java SE 5 @annotations.
If you want examples or help trying this out... let me know. JSFTemplating pages can be mixed with JSPs as well... although once you start using JSFTemplating pages, you're not likely to make any more JSP pages.
Good luck!
Ken Paulsen
https://jsftemplating.dev.java.net
Any thoughts?