问OSGI DS @Reference中的Atomicreference

EN

@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);
    }

@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;
    }