title: When are @PrePassivate and @PostActivate annotations useful?
body: <p>I have seen the <a href="https://docs.oracle.com/javaee/7/api/javax/ejb/PrePassivate.html" rel="nofollow noreferrer"><code>@PrePassivate</code></a> and <a href="https://docs.oracle.com/javaee/7/api/javax/ejb/PostActivate.html" rel="nofollow noreferrer"><code>@PostActivate</code></a> annotations in every EJB tutorial, but I don't see how are they useful. What would be an scenario where I need those?</p>