Session Beans and EJB3 vs Spring

Answer 1

I don't think there are many cases when the use of EJB 3 instead of Spring is absolutely necessary, but there are cases when using EJB 3 would be considerably easier. As the article states, the main advantages of EJB is the integration with the various other JEE technologies and, as of EJB 3, Enterprise Beans are much simpler to write than in they were in previous versions of the spec.

The classic reason for using EJB over POJOs or other middleware technologies is transactions. If your business logic needs to be transactional then EJB provides simple, declarative transnational demarcation and seamless integration with JTA via the container. While the article suggests that support for clustering, load balancing and performance management is an advantage, this is very much dependant on your choice of JEE application server.

I'd say the key factor in deciding whether to use Spring or EJB 3 is your container. If your target container is a fully JEE 5+ compliant application server and you need support for services such as transactions or messaging then EJB 3 is the obvious choice. If, however, you don't need to integrate with other JEE technologies or are deploying to a light-weight app server then using EJB would simply add unnecessary overhead.

Answer 2

Looks like yet another JEE vs. Spring post...

EJB/JEE and Spring are now two mature, competitive Java-based technology stacks. Often there's no reason to complicate things and mix them up. EJB actually learned and used many ideas from Spring et al.

Neither of them drives you into the XML/configuration hell. Both are fairly easy to get started with, at least with the very basic stuff.

Spring is more than just IoC/SOA/transactions. It's more like a toolbox - it's ready to integrate with, or directly provides, frameworks for ORM and transactions, web/MVC, security, timers/scheduling etc. You can pick exactly the pieces you need. You're not forced to use a container (you can use it in your standalone "desktop" app).

EJB is part of JEE stack. It is, well, the standard. It's not as broad, flexible as Spring, but it's by definition supported by all JEE containers.

I prefer Spring for the freedom and being one step ahead.