使用生成器创建应用程序范围的类成员 [英] Creating application scoped class member with a producer

问题描述

是否可以说，在下面的代码中，Hazelcast实例将是应用程序作用域？

Is it true to say that in the code bellow, the Hazelcast instance will be application scoped ?

@ApplicationScoped
public class Producer {

    private HazelcastInstance instance;

    @PostConstruct
    public void afterCreate() {
        instance = Hazelcast.newHazelcastInstance();
    }

    @Produces
    public HazelcastInstance getInstance() {
        return instance;
    }
}

编辑

此解决方案：

1. 确保生成的是应用程序作用域。


2. 提供优雅的Hazelcast关闭。

@ApplicationScoped
public class Producer {

    private HazelcastInstance instance;

    private Producer() {}

    @PostConstruct
    public void afterCreate() {
        instance = Hazelcast.newHazelcastInstance();
    }

    @PreDestroy
    public void beforeDestroy() {
        if(instance != null) {
            instance.shutdown();
        }
    }

    @Produces
    @ApplicationScoped
    public HazelcastInstance getInstance() {
        return instance;
    }
}

推荐答案

你生产者 bean将是应用程序作用域，这一点很清楚。
但是， HazelnutInstance bean将是 @Dependent 。

You Producer bean will be application scoped, that much is clear. However, HazelnutInstance bean will be @Dependent.

因此，如果您在代码中的某处执行 @Inject HazelnutInstance ，它将从CDI视点注入一个依赖实例。

Therefore, if you, somewhere in your code, do @Inject HazelnutInstance it will inject a dependent instance from CDI viewpoint.

但是你总是返回相同的实例，从不在生产者中创建新对象，所以理论上，你正在共享那个实例。

But you always return the same instance, never create new object in your producer, so theoretically, you are sharing that one instance.

然而，请留意豆生命周期！ @Dependent 当它们被注入的bean被销毁时，它们将被销毁。所以现在假设这样的破坏尝试 - Weld将尝试销毁你的依赖bean并将调用 @PreDestroy （在经典bean上）或 @Disposes （在带有生产者的bean上）方法。

However, look out for bean lifecycles! @Dependent beans will be destroyed when the bean where they were injected is destroyed. So now assume it comes to such destruction attempt - Weld will try to destroy your dependent bean and will call @PreDestroy (on "classic" beans) or @Disposes (on beans with producers) method on it.

因此，在你的情况下，如果有一个处理器方法某处，处理 HazelcastInstance ，这可能会导致麻烦，因为每次Weld试图销毁/处置该依赖bean时都会调用它。

Therefore, in your case, if there is a disposer method somewhere, which handles HazelcastInstance, that might cause a trouble as it would be invoked every time Weld attempts to destroy/dispose of that dependent bean.

IMO你会好过的话你制作 HazelcastInstance 应用范围。例如，

IMO you would be better off if you make HazelcastInstance application scoped. E.g.

@Produces
@ApplicationScoped
public HazelcastInstance getInstance() {
   return instance;
}

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