what is none scope bean and when to use it?

Question

could some explain what a none scope is and purpose of it?

Suppose if i have a bean in

request scope as r1

session scope as s1

application scope a         


        

Answer 1

A bean with a <managed-bean-scope> of none or a @NoneScoped annotation will be created on every single EL expression referencing the bean. It isn't been stored by JSF anywhere. The caller has got to store the evaluated reference itself, if necessary.

E.g. the following in the view

<p>#{noneScopedBean.someProperty}</p>
<p>#{noneScopedBean.someProperty}</p>
<p>#{noneScopedBean.someProperty}</p>

on a none-scoped bean will construct the bean 3 (three) times during a request. Every access to the bean gives a completely separate bean which is been garbaged immediately after the property access.

However, the following in for example a session scoped bean

@ManagedProperty("#{noneScopedBean}")
private NoneScopedBean noneScopedBean;

will make it to live as long as the session scoped bean instance. You should only make sure that you access it in the view by #{sessionScopedBean.noneScopedBean.someProperty} instead.

So it may be useful when you want scope-less data being available as a managed property in an arbitrary bean.

Answer 2

@NoneScoped would be beneficial in the following scenario.

Assume that we have to inject the same bean in two different scoped beans, we can mark that bean as @NoneScoped. Say a bean BeanOne with @NoneScoped can be easily injected in any bean with any scope like @Request or @Session.

Without using @NoneScoped for BeanOne, we may have to duplicate the bean with different scopes and inject them accordingly.

Answer 3

I'm using @nonescoped when my "view logic" dont need to be in any scope but be referenced by another ManagedBean.

I'm working with Liferay, as I want to make my architecture and design independent of liferay, I create my services interfaces and Dto, but when you need to persistence data, Liferay need that the companyId and companyGroupId be sended from the view layer (in this case JSF).

To maintain independence, I did a "Adapter pattern" creating a ServiceLayer ManagedBean with @noneScope with an interface independent from Liferay. This way I can get the companyId and the companyGroupId needed by the Liferay Apis.

The advantage of using @noneScope is that you can use it as a @ManagedProperty in any bean of any scope.