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  1. CDI Specification Issues
  2. CDI-248

Provide means to observe a group of qualified events ("Qualifier Inheritance"?)

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Details

    • Feature Request
    • Resolution: Obsolete
    • Minor
    • TBD
    • None
    • Concepts, Events
    • None

    Description

      We have been using CDI events for application development quite extensively. For instance we use events to propagate entity lifecycle events (@Created/@Updated/@Deleted Customer customer) or GUI selections (@Selected/@Deselected Customer customer) and implement related business logic in event observers. (e.g. send email for newly created customers, clear cached values on select/deselect/create/update/delete ...).

      This works quite well, however we have noticed that especially our JSF Presentation Tier contains lots of observer methods implementing the same behavior for a group of related CDI events.

      Example:

      public class XyzBean {
      
       public void onCustomerCreate(@Observes @Created Customer customer) { reset();} 
       public void onCustomerUpdate(@Observes @Updated Customer customer) { reset();} 
       public void onCustomerDelete(@Observes @Deleted Customer customer) { reset();}
       
      }
      

      Looks ugly, doesn't it?

      The above example could be improved if CDI would be able to observe a group of qualified events, e.g. public void onCustomerLifeCycleEvent(@Observes @LifeCycleChange Customer customer)

      { reset(); }

      - ignore method and qualifier names for now.

      Since Java does not support annotation inheritance grouping could be achieved using "qualified qualifier annotations":

      @Qualifier
      public @interface LifeCycleChange
      
      @Qualifier
      @LifeCycleChange
      public @interface Created
      
      @Qualifier
      @LifeCycleChange
      public @interface Updated
      
      @Qualifier
      @LifeCycleChange
      public @interface Deleted
      
      
      @Qualifier
      public @interface SelectionChange
      
      @Qualifier
      @SelectionChange
      public @interface Selected
      
      @Qualifier
      @SelectionChange
      public @interface Deselected
      

      WDYT? Side effects? Problems?

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            Unassigned Unassigned
            french_c Jens Schumann (Inactive)
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              Updated:
              Resolved: