Can EJB2 and EJB3 coexists in one application?

Question

does anybody know if it is possible to iteratively replace EJB2.1 beans with EJB3 beans in Java EE application?

That is: at one time remove one 2.1 bean from the co

Answer 1

Migration is possible, though it is not without hiccups.

Start with upgrading the descriptor to the Java EE 5 schemas. This is usually the flag that servers use to determine if they need to scan for annotations.

Once you have the descriptor upgraded (but otherwise unchanged), you can start migrating your Session and Message Driven Beans into Java EE 5 beans. As you convert a bean, you can also remove it from the deployment descriptor, if you want.

After all your other beans are done, you can start to work on removing your entity beans and converting the persistence to JPA entity classes. This is the non-trivial part of the exercise.