@PostConstruct和继承的顺序

Question

Let's suppose we have the following classes

public abstract class AbstractFoo {

    @PostConstruct
    private void doIt() {
       //
    }
}

public class Foo extends AbstractFoo {

    @PostConstruct
    private void doIt() {
       //
    }
}

When AbstractFoo.doIt() and Foo.doIt() will be called - what is the order?

Answer 1

@PostConstruct is the last thing to get executed in the initialization of a given managed bean, relative to its position in the inheritance chain. From the spec

The container must ensure that:

• Initializer methods (ie @PostConstruct ) declared by a class X in the type hierarchy of the bean are called after all injected fields declared by X or by superclasses of X have been initialized.

• Any @PostConstruct callback declared by a class X in the type hierarchy of the bean is called after all initializer methods declared by X or by superclasses of X have been called , after all injected fields declared by X or by superclasses of X have been initialized.

Pro Tip: With CDI 2.0, you can use @Inject to declare an initializer method as an alternative @PostConstruct and the restriction that you can have only one in a given class. The difference here is that @PostConstruct is still executed last and is the only place you can be guaranteed that all injected components will be available.