As an alternative design, appenders doing serialization such as SocketAppender and JMSQueue/JMSTopicAppender can delegate the serialization transformation to a sub-component. This way, the ILoggingEvent interface need not know about serialization at all. The SDOAware interface can be thus removed. Much cleaner. Ceki Gulcu wrote:
Joern Huxhorn wrote:
On 25.02.2009, at 19:33, Ceki Gulcu wrote:
The SDOAware interface contains a single method:
public interface SDOAware { Serializable getSDO(); }
It's not necessary for the SDO to implement Serializable. This is only necessary if serialization using ObjectOutputStream is used as the persistence method, and this should be an implementation detail hidden from the API.
The getSDO() returns a Serializable precisely because certain logback classes such as SocketAppenderBase in logback-core, and JMSQueue/JMSTopicAppender in logback-classic require serializable objects just before handing them over to an ObjectOutputStream.
So as it currently stands (revision 2170), the LoggingEvent hierarchy assumes that you can transform a LoggingEvent into a corresponding serializable LoggingEvet. As things stand as of revision 2170, serialization is not an implementation detail but actually leaks from ILoggingEvent interface (because it extends SDOAware).
I don't personally like this leakage but it is there. I welcome ideas about alternative designs where serialization is really an implementation detail.
To give an idea, I've looked at adding a writeResolve method in LoggingEvent so as to replace the current LoggingEvent instance with a LoggingEventSDO instance. This would obviate the need for the SDOAware interface. However, the cost of serialization performance is degraded by about 30% which seems to steep a price.
Beside that, DTO (http://en.wikipedia.org/wiki/Data_Transfer_Object) would probably be a better name since it is known to a wider audience.
Indeed, SDO is probably not a good name. However, aren't DTOs a mechanism to aggregate data so as to minimize the number of EJB calls? Also, are DTOs serializable by definition? (I guess they are.) Maybe VO (Value Object) is a better name than SDO...
Regards, Joern.
-- Ceki Gülcü Logback: The reliable, generic, fast and flexible logging framework for Java. http://logback.qos.ch