[jboss-user] [JBoss Seam] - Seam-managed persistence context

[wschwendt]

"matt.drees" wrote : 
  | I think nested conversations need to be discussed more.

I have the same opinion.


"jacob.orshalick" wrote : Maybe an expert on the effects of nested conversations on a Seam managed persistence context could shed some light on this?

I'm anything but an expert regarding the effects of nested conversations on a Seam-managed persistence context.   So far my understanding (could be wrong) is that a Seam-managed persistence context corresponds to 
an instance of the org.jboss.seam.persistence.ManagedPersistenceContext component.   This is a conversation-scoped component,  hence it can be injected into other components using the @In annotation.      Unlike "normal" conversation-scoped components, ManagedPersistenceContext  is annotated with @BypassInterceptors and @Install(false) however.    To define a managed persistence context with the name "entityManager", the typical idiom is that the framework user puts a component definition in config-file components.xml


  |   // components.xml
  |  
  |  <persistence:managed-persistence-context 
  |           name="entityManager" 
  |           persistence-unit-jndi-name="java:/contactlistEntityManagerFactory"/>
  | 

How does a Seam-managed persistence context get instantiated?   It gets instantiated like any ordinary Seam component.   For example, the Seam CRUD framework classes EntityHome and EntityQuery both extend
 org.jboss.seam.framework.PersistenceController which creates a Seam-managed persistence context effectively via a call of Component.getInstance(name);

Now what happens if a nested conversation is in progress and there is an injection such as the following or another call of Component.getInstance("entityManager")?


  | @In EntityManager entityManager; //a Seam-managed persistence context
  | 

I'd say the usual rules for injections apply, that means Seam tries a hierarchical context search.      A nested conversation has read-only access to the context of the outer conversation.   Therefore, if a Seam-managed persistence context was instantiated already in the parent conversation, the hierarchical search finds it and the nested conversation thus shares the same persistence context with the parent conversation.     



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