Phanidhar Adusumilli wrote:
Section 3.1.5 of the JSF specification, recommends not use component bindings at session/application scope. What are the issues in binding components to manged beans at session/application scope?
A UIComponent object has references to its parent and all its children. Therefore if you store a reference to any UIComponent in a session-scope bean then the entire component tree for a particular view is kept in memory.
Session-scope backing beans are generally a bad idea anyway; they waste memory as they are created when a user accesses some view then hang around until the user logs out even if the user never revisits that view. If this object has a reference to a UIComponent, therefore keeping an entire component tree in memory too (see above) then that's even worse. There are some cases where session-scoped beans are appropriate but normal "backing beans for views" should be request-scoped wherever possible.
Referencing a component from an application-scope bean (ie one shared between users) just makes no sense at all. Components are not thread-safe but application-scope beans are shared between users and therefore must be thread-safe.
