java - OSGI DS @Reference 中的原子引用

Question

我正在编写一个 OSGI 应用程序，其中包括动态和静态引用。每个服务都放置在不同的 bundle 中。

@Reference (bind = "bindMethod", unbind = "unbindMethod", cardinality = ReferenceCardinality.MANDATORY_UNARY, policy = ReferencePolicy.DYNAMIC)
    private final AtomicReference<TestService> testService = new AtomicReference<TestService>();

@Reference (bind = "bindMethod", unbind = "unbindMethod", cardinality = ReferenceCardinality.MANDATORY_UNARY, policy = ReferencePolicy.DYNAMIC)
    private AtomicReference<TestService> testService = new AtomicReference<TestService>(); //final is ommitted

 protected void bindMethod(TestService atestService)
    {
        if (TestService.get() == null)
        {
            testService.set(atestService);
        }
    }

    protected void unbindMethod(TestService atestService)
    {
        myServices.compareAndSet(testService, null);
    }

没有原子引用

@Reference (bind = "bindMethod", unbind = "unbindMethod", cardinality = ReferenceCardinality.MANDATORY_UNARY, policy = ReferencePolicy.DYNAMIC)
    private TestService testService;

protected void bindMethod(TestService atestService)
    {
        testService = atestService;
    }

    protected void unbindMethod(TestService atestService)
    {
        testService = null;
    }

建议使用哪一种？每种对性能的影响是什么？

Answer 1

事实上，您将 @Reference 放在字段上意味着您正在使用 DS 1.3 及其新的字段注入(inject)支持。

在这种情况下，您不需要绑定(bind)/取消绑定(bind)方法，也不需要 AtomicReference。只是:

@Reference 私有(private) volatile TestService testService；

volatile 意味着它是动态引用，并且还提供适当的并发访问。