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Prepare for New EJB 3.0 Persistence
See how to address the migration concerns of enterprise application developers and architects who are currently using EJB 2.1 CMP
by Merrick Schincariol and Doug Clarke
June 22, 2005
Much has already been much written and discussed concerning the upcoming changes to Enterprise JavaBeans (EJB) with the proposed 3.0 specification. The simplifications of the component model and metadata configuration will definitely make this update an important evolution of J2EE. One of the most significant changes within EJB 3.0 is the new persistence model. This new persistence API and approach to modeling is based on the success of leading object-relational mapping products that use a Plain Old Java Object (POJO) approach to persistence.
We'll look into EJB 3.0 persistence and address the concerns of enterprise application developers and architects who are currently using EJB 2.1 CMP. The process of moving from EJB 2.1 persistence to EJB 3.0 can range from coexistence to a full migration and adoption of the new model. Although much has already been written about the new persistence model, specific strategies and development and design patterns have not been detailed. We'll attempt to fill these gaps with concrete solution options while visiting the key benefits that application developers will gain through this migration. We assume that you are familiar with the basic elements of the new persistence API. (Note: Look for an upcoming article on migrating J2EE applications to EJB 3.0 in Java Pro magazine by Debu Panda, a member of the Oracle Application Server Development team, that will post on FTPOnline in July, 2005.)
Why Migrate?
One question participants in J2EE projects should discuss when planning an upgrade to an EJB 3.0-enabled J2EE container is: Why should we migrate our application? These new EJB 3.0 containers will be backward compatible and thus support their existing application without modification. This backward compatibility means that upgrading a container to EJB 3.0 does not mean in itself that an application needs to be rewritten. However, what about this new persistence API?
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