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:

• session

• conversation

Java EE component scopes:

• Singletons

• Statless

• Objects to be explicitly created / destroyed by client:

  • • JavaBeans components

    • stateful session beans

• • state is shared by explicit reference passing between clients

• However, if a Java EE component is a managed bean, it becomes a scoped object