@PostConstruct的执行顺序 [英] Execution Order of @PostConstruct

问题描述

我的JEE应用程序中有2个单例，我想在启动时进行初始化。像这样的东西：

I have 2 singletons in my JEE application that I want to initialize at start up. Something like this:

@Singleton
@Startup
public class ServiceB {

    @EJB
    private ServiceA a;

    @PostConstruct
    private void init() {
        ....
    }
}

ServiceB并不需要ServiceA，我只是添加了依赖项以确保ServiceB初始化之前ServiceA已完全初始化（读取：@ PostConstruct-method完成）。 （）-方法开始。

ServiceB doesn't really need ServiceA, I just added the dependency to make sure that ServiceA is fully initialized (read: @PostConstruct-method finished) before ServiceB's init() -Method starts.

但是它不会等待。 ServiceB实际上在ServiceA之前启动。

But it doesn't wait. ServiceB actually starts before ServiceA.

有没有办法确保一个Bean的@ PostConstruct-方法等待另一个Bean的@PostConstruct方法完成？

Is there any way to ensure that one Bean's @PostConstruct- method waits for another Bean's @PostConstruct-method to finish?

我知道我可以删除ServiceA中的@PostConstruct批注并直接从ServiceB中调用它。

I know I could just remove the @PostConstruct Annotation in ServiceA and call it directly from ServiceB

    @PostConstruct init() {
        a.init();
    }

但是我有没有ServiceB的部署。因此，我不能依靠ServiceB来初始化ServiceA。 ServiceA必须自己做。并且ServiceB必须等待ServiceA完成。

but I have deployments where there is no ServiceB. So I can't rely on ServiceB to init ServiceA. ServiceA has to do that itself. And ServiceB must wait for ServiceA to be done with it.

推荐答案

使用 @ DependsOn 批注声明对启动bean的初始化依赖性。

Use the @DependsOn annotation to declare an initialization dependency on startup beans.

示例：

@Singleton
@Startup
public class ServiceA {
    @PostConstruct
    public void init() { ... }
}

@Singleton
@Startup
@DependsOn("ServiceA")
public class ServiceB {
    @EJB
    ServiceA a;

    @PostConstruct
    public void init() { ... } // will be called after a is initialized
}

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