jakarta-ee - @PostConstruct之后初始化子类

Question

我在 WildFly 8.2 应用程序服务器中使用 JavaEE 7 中的上下文依赖注入(inject) CDI 1.1 框架

我想在父类(super class)的 @PostConstruct 之后初始化子类

所以我做了类似的事情

// case 1: it's working but it's not simple to understand

public class A {

    @PostConstruct
    protected void init() {
        System.out.println("A");
        afterInit();
    }

    protected void afterInit() {}

}

public class B extends A {

    @Override
    protected void afterInit() {
        System.out.println("B");
    }

}


public class C extends B {

    @Override
    protected void afterInit() {
        super.afterInit();
        System.out.println("C");
    }

}

因此init()方法将按此顺序打印A、B、C

如果有一个 @AfterPostconstruct 注释可以做同样的事情，但我不知道

// case 2: dream code

public class A {

    @PostConstruct
    protected void init() {
        System.out.println("A");
    }

}

public class B extends A {

    @AfterPostConstruct  // pseudocode
    protected void afterInitB() {
        System.out.println("B");
    }

}


public class C extends B {

    @AfterPostConstruct // pseudocode
    protected void afterInitC() {
        System.out.println("C");
    }

}

我尝试重写 init() 但它不起作用(init() 未被容器调用)

// case 3 : code that is not working but it would be better than case 1

public class A {

    @PostConstruct
    protected void init() {
        System.out.println("A");
    }

}

public class B extends A {

    @Override
    protected void init() {
        super.init();
        System.out.println("B");
    }

}


public class C extends B {

    @Override
    protected void init() {
        super.init();
        System.out.println("C");
    }

} 

在@PostConstruct之后是否有更好(更简单)的方法来初始化子类？

Answer 1

根据 JSR 318 - Interceptors 1.2 的在目标类上声明的拦截器的调用顺序部分(也适用于 CDI 1.1)规范:

Interceptor methods declared on the target class or its superclasses are invoked in the following order:

• If a target class has superclasses, any interceptor methods defined on those superclasses are invoked, most general superclass first.
• The interceptor method, if any, on the target class itself is invoked.

If an interceptor method is overridden by another method (regardless of whether that method is itself an interceptor method), it will not be invoked.

因此，在您的用例中，您可以编写:

public class A {

    @PostConstruct
    private void initA() {
        System.out.println("A");
    }
}

public class B extends A {

    @PostConstruct
    private void initB() {
        System.out.println("B");
    }
}

public class C extends B {

    @PostConstruct
    private void initC() {
        System.out.println("C");
    }
} 

并按顺序打印:A、B、C。