HK2工厂实现单例

Question

我正在尝试理解泽西应用程序中的HK2工厂实现。

目标:如何实施单件工厂？

    // Below is the simple factory implementation

    public class MyFactory implements Factory<SomeObject> {

        private static final Logger logger = LoggerFactory.getLogger(MyFactory.class);
        private final CloseableService closeService;

        @Inject
        public MyFactory(CloseableService closeService) {
            this.closeService = closeService;
        }

        @Override
        public MyFactory provide() {
            logger.debug("provide object from MyFactory");
            SomeObject objectFromFactory = new SomeObject();
            this.closeService.add(() -> dispose(objectFromFactory));
            return objectFromFactory;
        }

        @Override
        public void dispose(SomeObject instance) {
            // destroy instance
             logger.debug("dispose object from MyFactory");
        }
    }

    // and binding
     bindFactory(MyFactory.class).to(SomeObject.class).in(Singelton.class);

     // to check object creation and destruction
     bind(HK2InstanceListener.class).to(InstanceLifecycleListener.class).in(Singleton.class);

    // and injecting in some resource class

    @Inject
    SomeObject useThisObject;

    //updated information 

    AbstractBinder abstractBinder = configureBinder();

    ServiceLocator appServiceLocator = configureHK2(abstractBinder);

    public static AbstractBinder configureBinder() {
            return new AbstractBinder() {
                @Override
                protected void configure() {
         bindFactory(MyFactory.class).to(SomeObject.class).in(Singelton.class);

           // to check object creation and destruction
         bind(HK2InstanceListener.class).to(InstanceLifecycleListener.class).in(Singleton.class);

         }
         }

    public ServiceLocator configureHK2(AbstractBinder binder) {
            ServiceLocatorFactory factory = ServiceLocatorFactory.getInstance();
            ServiceLocator locator = factory.create("my-test-server");

            DynamicConfigurationService dcs = locator.getService(DynamicConfigurationService.class);
            DynamicConfiguration dc = dcs.createDynamicConfiguration();

            locator.inject(binder);
            binder.bind(dc);
            dc.commit();
            return locator;
        }

在启动应用程序时，我在下面的日志中看到

    10:38:34.122 [grizzly-http-server-0] DEBUG com.test.HK2InstanceListener - HK2 before object create : com.test.MyFactory
    10:38:34.125 [grizzly-http-server-0] DEBUG com.test.HK2InstanceListener - HK2 before object create : com.test.MyFactory
    10:38:34.125 [grizzly-http-server-0] DEBUG com.test.HK2InstanceListener - HK2 after object create : com.test.MyFactory
    10:38:34.125 [grizzly-http-server-0] DEBUG com.test.MyFactory provide - object from MyFactory
    10:38:35.700 [grizzly-http-server-0] DEBUG com.test.HK2InstanceListener - HK2 after object create : com.test.MyFactory

    10:38:37.743 [grizzly-http-server-0] DEBUG com.test.MyFactory - dispose object from MyFactory

1. 当作用域= Singleton

- creating two objects of MyFactory
- Next request fails with null pointer exception @Inject.

​

1. 当作用域= RequestScoped，PerLookup

- Every request creates two objects of MyFactory

​

我理解单例工厂是一个单一的工厂对象(MyFactory)，它在注入时提供某种对象。

那么，(1)应该工作还是我错过了什么？

为什么是工厂的两个对象？

有什么建议吗？提前谢谢。

HK2 Version : 2.5.0-b60
Jersey Version: 2.26

关于NPE的附加信息

它不是来自HK2，而是.in(Singleton.class)和.in(PerLookup.class)之间的行为差异。

// SomeObject looks like

Class SomeObject
{

    private Stack<String> someStack; 

     public SomeObject() {

        // this may be the issue for Singleton
        this.someStack = new Stack();
    }

    public someOperation(String stackIt)
    {
        // NPE location
        this.someStack.push(stackIt);
    }
}

以下位置的NPE

bindFactory(MyFactory.class,Singleton.class).to(SomeObject.class).in(Singleton.class);

没有NPE在上面的位置当下面

bindFactory(MyFactory.class,Singleton.class).to(SomeObject.class).in(PerLookup.class);

Answer 1

在执行bindFactory时，使用第二个参数将Factory绑定为Singleton。您所做的方式--仅提供方法--绑定为Singleton。因此，为了使工厂本身也成为一个单身汉，可以这样做：

bindFactory(MyFactory.class, Singleton.class).to(SomeObject.class).in(Singelton.class);

这应该得到了提供的东西和工厂本身作为单身汉的约束。