Yeah,
Shale is indeed a nice enhancement for use cases like that. init() is much *clearer* than defining stuff inside a constructor.
-Matthias
[EMAIL PROTECTED] wrote:
You might take a look at Shale. It addresses this problem by defining a ViewController interfaces that defines extra lifecycle methods. init() destroy() preprocess() prerender()
The ViewController is a managed bean that implements this interface. There is also an abstract class that you can inherit from, AbstractViewController.
There is an assumed mapping between the managed beans name, the view id and the ViewController instance. It uses a filter and a phase listener to invoke these callback methods to a managed bean/ ViewController.
It’s pretty cool, http://wiki.apache.org/struts/StrutsShale
Gary
Sure. Lazy initialization is a good pattern to follow, but if you have a lot of getters using the same data it can be ugly to put checks in a lot of different places. If it's just the one property, then lazy initialization is definitely the way to go.
It'd be nice if a bean could optionally implement some managed bean interface and there'd be onInitialize() method that would get called automatically if bean so wished (i.e. implements the interface). The same approach could be used for a lot of other cases as well.
Kalle
-----Original Message-----
From: David Gadbois [mailto:[EMAIL PROTECTED] Sent: Friday, March 11, 2005 3:31 PM
To: MyFaces Discussion
Subject: Re: How to execute bean method before JSF page is loaded?
The pattern I have been using for this sort of thing it to have the value accessor in the bean check to see if the data has been retrieved and, if not, sets the value up. E.g.,
public class SomeBean { private Object value = null;
public Object getValue() { if (value == null) { // Initialize value } return value; }
public void setValue(Object value) { this.value = value; } }
The data table then accesses the value through the getter:
<h:dataTable var="item" value="#{someBean.value}">
You could use a PhaseListener on the Render Response phase (and JSF 1.2 will have listeners that can be more conveniently attached to a particular view), but then you may run into problems if some other view logic needs to access the value in a prior phase. For this reason, I have found most recommendation for using a PhaseListener to be wrong-headed.
--David Gadbois
Jonathan Eric Miller wrote:
Does anyone know if there is a recommended way to have a
bean method
executed before a JSF page is loaded? For example, I have a
page with
a h:dataTable in it. What I want to do is make it so that
when a user
brings up the page directly (by entering the URL in the
browser text
box rather than as the result of submitting a form), a bean
method is
executed which does a query to a database. I want the bean to be populated before the page is rendered. Currently, I'm doing
this using
a servlet filter. However, one problem with this is that
Faces isn't
initialized at this point. This isn't a big issue, but, one
issue that
I ran into is that I was using a managed bean and that bean
might not
have been created by Faces when the filter executes. So, I put some code in to test if the bean is null or not and it creates it if necessary. I'm wondering if there is a more recommended way
to do this
within the context of Faces itself. i.e. maybe using a listener or something? Note, I only want the code to execute for a
specific page.
It seems like there should be some kind of onInit() method
that could
be overriden to perform initialization before a page is
renderered...
I don't know much about ASP.NET, but, I think it allows you to do something like this. I guess I could use a scriptlet in the
JSP to do it.
Jon
