Monday, July 01, 2013

CDI vs. Spring Framework Core

Another question I got in my Spring Framework training is: is it worthwhile to switch from Spring Framework 3.x to CDI with JBoss Weld or Apache OpenWebBeans implementation?

After googling around I found some good articles and blogs about this topic. These two articles are the best in my opinion:
Luckily I had a chance to take a CDI course intensively for two days to be able to see what we actually could do with CDI. After doing two days intensive course of CDI I can sum up this topic as following:
  • CDI takes a lot of good idea of Spring Framework, this is for sure.
  • Anything you can do with CDI (I used JBoss Weld in the course I followed) is not new and you can have those stuffs in Spring Framework as well.
  • In CDI 1.0 (JEE 6) there is still a lot of things which is not supported natively such as "scanning of classes and packages" to turn on the dependency injection. Sure you can use CDI portable extensions to support such a functionality but the problem with those extensions is just like Eclipse plugins: you never know whether all of the plugins can work smoothly together if they are not written by one person or one vendor.
Additionally to the articles and blogs above I found following extensions for Spring Framework to support following CDI mechanism:
(1) Events with @Observes: take a look at this Open Source project which extends Spring capability: spring-event-annotations.

(2) Decorator with @Decorator and @Delegate: take a look at this blog and Open Source project: JSR-299 CDI Decorators for Spring beans.

(3) Interceptor with @Interceptor, @InterceptorBinding, @AroundInvoke and @Nonbinding: take a look at this article: JSR-299 CDI Interceptors for Spring Beans.

(4) Custom bean scope: take a look at this article: Custom scopes in CDI 1.0 and Spring 3.1.

(5) Type-safe injection: take a look at this blog: Type-safe dependency injection in Spring 3 IoC-Container.

At the end I have to admit that you won't miss anything if you are using Spring Framework. It is definitely more mature than any other Context and Dependency Injection containers available on the market. So if you ask me whether it is worthwhile to switch from Spring Framework Core to CDI implementation like JBoss Weld I would say: no.There is also no economically reasons to switch to CDI implementation if you are already use Spring Framework. Try explain to your management that you want to switch to CDI just because it is standard, no other advantages and also with less functionality and maturity. Surely you should use the standard Annotations within Spring Framework, so instead of @Autowired you should use @Inject for example. In some ways I see Spring Framework Core as "the" reference implementation of CDI specification.