I am not sure if I agree with Daniel's specific use case, but I think it would be very helpful to have page-specific configuration for managed beans. In particular, it would be nice if there were a way to ensure that a managed bean was loaded
and initialized before the page was invoked.
Here is my scenario. You have a view that needs to display data, so your managed bean needs to perform database operations, probably in your getters:
public void getProduct() throws Exception {
if (this.product == null) {
this.product = // Load from database
}
return this.product;
}
As it stands now, any errors caused by failed database access will be thrown as you walk through your JSF binding expressions:
{#ProductController.product.price}
If the product fails to load, the getProduct() method fails and you get hideously ugly Expression Language error messages that completely munge the real cause.
If there were mechanism to pre-load a bean when a page was invoked and pre-initialize your managed properties, you could load your data in the managed property setters instead:
public void setProductId(Long id) throws Exception {
// Load product using its id
}
Since all of this is happening before your view page is executing, you ought to be able to cleanly and generically catch any errors and report them in a simple manner, using an error-page mechanism similar to JSP:
<managed-bean>
<managed-bean-name>ProductController</managed-bean-name>
<managed-bean-class>....ProductController</managed-bean-class>
<managed-bean-scope>request</managed-bean-scope>
<managed-property>
<property-name>productId</property-name>
<value>#{param.productId}</value>
</managed-property>
<load-before>showProduct.jsp</load-before>
<error-page>
<exception-type>java.sql.SQLException</exception-type>
<location>databaseError.jsp</location>
</error-page>
</managed-bean>
