FROM AN ARTICLE "TopLink is fast, nimbly maps complex relationships, and provides both EJB-like and nearly transparent Java models. But Oracle recently acquired TopLink, and Oracle is regrettably both a database vendor and an application server vendor. If you're a WebLogic customer or use a non-Oracle database, you're going to want to think long and hard before buying TopLink. It's still a great product for pure Oracle customers, but others simply must protect themselves against a potential change in direction of TopLink. Of course, you may choose to buy another proprietary OR mapper instead. The problem is that you'd then be buying a proprietary product with less-than-compelling market share. You'd have to pay more for training, experienced developers, and aftermarket tools. While TopLink has been king for a day, many customers will want to look away from the proprietary relational mappers".
Hibernate is the open-source darling
If you're looking for a good persistence framework and you like open-source software, you owe it to yourself to check out Hibernate. It's a lightweight persistence framework that's gathered quite a following. Like JDO, it works well with WebLogic, with or without EJB. It has several fundamental strengths:
� Hibernate uses Java reflection instead of byte code enhancement to achieve transparency.
� Hibernate performance is surprisingly good because it is such a lightweight framework.
� The mapping flexibility is outstanding. It has good support for several relational databases, with complex relationships ranging from one-to-one to many-to-many.
Hibernate too has some disadvantages. It puts some limitations on your object model. (For example, one persistent class cannot map to more than one table.) The combination of a proprietary interface and smaller market share is also disconcerting, but Hibernate seems to have mitigated that risk by establishing good momentum. Other open-source persistence frameworks exist as well, but none with the momentum of Hibernate.