@PostConstruct annotation and spring lifecycle

Question

I'm new to Spring, I would like to know:

I have a java class annotated with @Component (spring) and inside I have a method annotated with @PostConstruct. The class is then referenced by @Autowired annotated field in another class. Can I assume that the class is only injected after @PostConstruct is called?

@Component class AuthenticationMetrics {      private static final MetricRegistry metrics = new MetricRegistry();      final Counter requestsTotal;      final Meter guestLogins;      final Meter kfUserLogins;      final Timer guestLoginResponseTime;      final Timer kfLoginResponseTime;      @PostConstruct     public void populateMetricsRegistry() {         metrics.counter("authentication.requests.totals");     } } 

Answer 1

If you are asking is injection of given class happening after @PostConstruct in that bean is called, then the answer is yes - @PostConstruct is executed before bean is considered as "injectable"

If you are asking if @PostConstruct on given bean is executed after all injections has been done (on the same bean) - then yes - @PostConstruct is executed after injections are commited to given bean. This is the reason it exists. Normally you could put @PostConstruct actions into the constructor. However, when new object is created (constructor is called) injections are not performed yet - so any initialization that depends on injected objects would fail due to NPE. That is why you need @PostConstruct