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I'm currently learning the new Java EE 6 component models and am confused with the latest dependency injection mechanism. So here are my questions: 1) What is the difference between @Inject and @EJB 2) If I have a simple POJO that contains another POJOs (which one of them is the DAO code), what would be the better choice: @Inject or @EJB? Can I mix @Inject and @EJB? An example would be: ClassA implements InterfaceA and has an instance of ClassA_Adaptor ClassA_Adaptor implements InterfaceAB and has an instance of ClassB ClassB implements InterfaceB and has an instance of ClassB_Adaptor and an instance DAO_ClassB ClassB_Adaptor implements InterfaceB and has an instance of ClassC ClassC implements InterfaceBC and has an instance of WebService_ClassC DAO_ClassB will use JPA 2.0 (@PersistenceContext) I'd like to inject all of them including the DAO and the WebService. 3) Is it a bad approach to only use transactional for certain operations but not for all? As an example: Some methods in DAO_ClassB are your typical query, while other methods are "write" methods. Is it bad to not wrap the "READ" methods with transaction? To my understanding, the DAO_ClassB can be wrapped with transaction using @EJB (inject the DAO_ClassB and make all methods transactional). How can I control it? Sorry if some of the questions are confusing because I know only bits and pieces of the Java EE 6 new component model.

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