CDI Bean Scope

Scopes

bean scopes: defines lifecycle of bean that is injected into another class; container automatically create / destroy / share scoped objects

@RequestScoped - in a single user HTTP request
- no need to be serializable
@SessionScoped
- in a user's interaction across multiple HTTP requests (a shopping cart)
- must be serializable
@ApplicationScoped
- shared state across all users' interactions
- must be serializable
@Dependent
- default scope if none is specified
- an object exists to serve exactly one client bean and has the same lifecycle as that client bean
- (my interpretation) one master one servant, created a new instance each time requested
@ConversationScoped
- a user's interaction with a servlet including JSF applications
- the conversation scope exists within developer controlled boundaries that extends across multiple requests for a long running conversations
- scoped to a particular HTTP servlet session and may not cross sessionboundaries
- must be serializable
Custom defined scopes (advanced topic)

Passivation and passivating scopes (see http://docs.jboss.org/cdi/spec/1.0/html/contexts.html)

Passivation: idle, stateful object temporarily transferred from memory to some secondary storage (hard-disk)

Passivation capable (not capable):

stateful session beans
(not) stateless and singleton
managed bean that is serializable (and all interceptors / decorators serializable)
producer method, if always returns passivation capable value
producer field, if always refers to a passivation capable value
PassivationCapable (interface)

Passivation capable dependencies: (skipped for now)

Passivating scopes: requires

beans with the scope are passivation capable
implementations of Contextual passed to any context object for the scope are passivation capable

Built-in scopes that are passivating scopes:

Java EE component scopes:

Singletons
Statless
Objects to be explicitly created / destroyed by client:
- - JavaBeans components
  - stateful session beans