Hello, i've been using JDO for the past while and as such have used lightweight value objects, created from persistence objects, to pass data to and from the web layer from the ejb layer. Because of the bytecode enhancement done in JDO, persistent classes can become quite heavy and therefore it's not desirable to be passing them around from web to ejb and vica versa. Does anyone care to comment on the merits or drawbacks of using a similar pattern when using hibernate at the persistence layer? Is it necessary? Does using runtime bytecode generation imply that the persistent objects themselves remain lightweight?

M@

Hibernate does not use bytecode manipulation to change your objects. (at least not in the sense JDO does). Runtime bytecode generation is mainly used to create Proxys and for reflection optimisation. So there is no need to use DTOs, it is usually much easier to just use the persistent classes and use hibernates detatched object support.