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)

- 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?