What is the difference between @Inject and @EJB

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  1. @EJB injects EJBs only, but @Inject can be used to inject POJOs rather than EJBs. However, @Inject requires that your archive be a BDA (contain beans.xml for EE 6, or implicitly in EE 7). @Inject also has additional CDI-specific capabilities (scopes, interceptors, etc.), but those capabilities incur extra overhead. Application servers have support for specifying @EJB bindings so that a deployer can choose the target EJB, but @Inject only allows the application developer to choose the target EJB (and it must exist in the application).

  2. If the target is not an EJB, then you must not use @EJB.

  3. It depends whether you’re making multiple inter-related queries and then attempting to make business decisions. You need to understand isolation levels and take them into consideration, even for read-only operations.

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