java - @PostConstruct 的顺序和继承

Question

假设我们有以下类

public abstract class AbstractFoo {

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

public class Foo extends AbstractFoo {

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

何时调用 AbstractFoo.doIt() 和 Foo.doIt() - 顺序是什么？

Answer 1

@PostConstruct是在给定托管 bean 的初始化中执行的最后 事情，相对于它在继承链中的位置。来自规范

The container must ensure that:

• Initializer methods (i.e. @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.

专业提示:对于 CDI 2.0，you can use @Inject to declare an initializer method作为替代 @PostConstruct 和在给定类中只能有一个的限制。这里的区别是 @PostConstruct 仍然最后执行，并且是唯一可以保证所有注入(inject)组件都可用的地方。