Managed Bean Best Practices

[arti <ar...@tambas.at>]

Hi
 
Are there any best practices for using Managed Beans?
 
We plan to use our own custom-built JSF components. Need to understand
how to design backing beans for performance/effort optimization.
For example :
 
1. How to make managed beans thread-safe for concurrent requests,
without compromising on efficiency/speed?
 
2. How to enforce the J2EE security with managed-beans?
 
3. How to decide the scope of these beans to ensure minimal data-storage
in session?
 
4. How to decide the granularity at which a managed-bean should be used
for example :
 
4.1 One bean-per-component
    Advantages :
   a) if complex components require special
data-holding/processing/event-handling capabilities from bean 
     (e.g. datagrid model,tree model,menu model)
    Problems :
 - with multiple components in a page/form 
    a) it becomes tedious to debug/change/track which bean serves which
component 
    b) if session scope is required, too many beans will be cached in
session
    c) unnecessarily too many beans will be created on server (= n pages
* m components-per-page)
    d) unnecessarily increases the length of faces-config.xml
 
4.2 One bean-per-form 
    Advantages :
    a) in multi-form web pages, to ensure the functional behaviour of
each form is separate/modular in its own bean. 
    b) each managed-bean would map to specific/meaningful
functionality/user-interaction in use-case.
 
    Problems :
 - if form includes complex components (datagrid/tree/menu) requiring a
specialised bean class, then 
   a) either one of the specialized bean has to be augmented with
additional logic to handle data/events for all other components within
the form
     (Not good, as it mixes-up the responsibilities of
component-specific-beans, and the bean may no more be reusable in
another form)
 
   b) or without using component-specific beans, only single form bean
should handle the data/events for all components in the form?
     (Neither good, since if a complex tree-compoent is reused in
multiple forms, then the logic to handle data/events for such a
component will be repeated in those many form-specific managed beans) 
 
4.3 One bean-per-page 
 Advantages :
   a) seems more modular/meaningful way - since a page would map to some
feature within the use-case
   b) bean will contain only behaviour which is relevent for the
associated page/function within use-case
 Problems :
   a) in multi-form pages, can single bean handle data/events for
multiple forms?
     b) if page uses complex component (e.g datagrid, tree) that needs
its own bean - how does page-bean exchange data with component-bean?
 
Thanks,
Arti