Option 1:

Write your own ExceptionHandlerFactory / ExceptionHandler (and register it in faces-config.xml). Have a look at Seam-Catch how they did it...

public class MyExceptionHandlerFactory extends ExceptionHandlerFactory {
...

public class MyExceptionHandler extends ExceptionHandlerWrapper {
...
     private HandledException handleException(Throwable t, FacesContext facesContext) {
          ResourceBundle messages = this.getMessageBundle(facesContext);
          List<Throwable> exceptionStack = this.createExceptionStack(t);
          for (Throwable cause : exceptionStack) {
               if (cause instanceof NonexistentConversationException) {
                    this.log.debugv(t, "Handling conversation timeout exception {0}", cause.getClass().getName());
                    return new HandledException(messages.getString("error.sessionTimeout"), cause);
               } else if (cause instanceof ViewExpiredException) {
                    this.log.debugv(t, "Handling session timeout exception {0}", cause.getClass().getName());
                    return new HandledException(messages.getString("error.sessionTimeout"), cause);
                  }
...
          }
          this.log.errorv(t, "Handling exception {0}", t.getClass().getName());
          return new HandledException(messages.getString("error.general"), t);
     }
...
}

Option 2:

Use Seam-Catch :-)

I used both options (Seam-Catch wasn't released back then), both workes...

Cheers,

Jan