Sun Microsystems has proposed a new data persistence model for Java that will fuse the focus of two Java specifications. The specifications in questions are, EJB (Enterprise JavaBeans) 3.0, JSR (Java Specification Request) 220; and JDO (Java Data Objects) 2.0, JSR-243.
Linda DeMichiel and Craig Russell, of Sun, called the effort a "reconciliation," and asked for support from the Java community. However, the move to reconcile persistence models could come at the expense of delays in the delivery of the next version of the Java 2 Enterprise Edition specification, J2EE 5.0, according to Sun officials.
The reason for seeking to unify the two specifications has to do with variations in EJB and JDO data persistence models. Data persistence refers to objects and data that continue to exist between runs of a program. There is no unified opinion among programmers regarding persistence models of both EJB and JDO. What Sun is leading a community-based effort to create is a single Plain Old Java Object (POJO) persistence model.
Dennis MacNeil, line manager for J2EE at Sun, explained the benefits of POJO, "The big news to the Java Technology Community is to give people an update on EJB 3.0. EJB 3.0 is all about ease of use, and as part of that we're going to Plain Old Java Objects [POJO] persistence model."
DeMichiel and Russell provided some background information relating to variations in persistence models that led to the decision. "For years, the Enterprise JavaBeans (EJB) and Java Data Objects (JDO) specifications have evolved independently. Even to this day, the data persistence models in EJB and JDO differ significantly. This divergence has caused confusion and debates among Java developers, and is not in the best interest of the Java community."
The new POJO specification is designed to run across both J2EE and J2SE. DeMichiel said that Sun decided to forge ahead with the initiative after seeing how strong a response EJB 3.0 was met with. She said, "it is good to converge the efforts."
In general, it appears that community support of the new initiative is there. Even among some Java developers who had at first criticized EJB 3.0, the reaction to POJO is more receptive. Rod Johnson, a London-based enterprise Java architect, J2EE consultant and author, was an early critic of EJB 3.0. However, the convergence of data persistence has promise, according to him.
Johnson said, "It's odd for EJB3 to be defining a persistence API applicable to J2SE. But overall I think it's promising. Everyone seems to agree that transparent persistence is important, and that POJO persistence is the future. The EJB expert group seems finally to accept that persistence should not be tied to the EJB container. Hopefully from here the focus will be on getting a good technical solution, rather than on politics."
