What does the @EJBs annotation do?

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The @EJB annotation (and @Resource, @WebServiceRef, etc.) serves two purposes:

  1. It declares a reference in the component namespace. For example, @EJB(name="myEJB") creates a reference java:comp/env/myEJB. If you annotate a field and do not specify a name, then it creates a reference java:comp/env/com.example.MyClass/myField.
  2. If the annotation is declared on a field or setter method, then the container performs injection when the component is created.

How the reference is resolved varies, independent of whether the reference is being resolved for a lookup("java:comp/env/myEJB") or due to injection:

  1. If EE 6+ is used, the lookup attribute requires a JNDI lookup to resolve the target.
  2. Some application servers support mappedName, which is specified to be vendor specific. This is usually implemented by performing a lookup.
  3. Application servers support bindings at deployment time. This is usually implemented by performing a lookup.
  4. If no other binding information is provided and the bean interface (beanInterface or the field type) is only implemented by a single EJB in the application, then the EJB specification requires that it fall back to that.
  5. If no other binding information is provided and #4 cannot work, some application servers will attempt to perform a lookup in the server namespace based on the ref name (for example, java:comp/env/myEJB might cause a lookup of myEJB in the server namespace).

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