CDI事件和泛型(CDI events and generics)

CDI事件和泛型(CDI events and generics)

我正在尝试发送事件并通常这样做。 我的意思是 - 创建一个具有泛型类型的抽象基础DAO类，并从其方法中触发事件。 这适用于所有后代。 如果我定义确切的类型，这是有效的，但如果我使用泛型，则不行。 我的意思是：

AbstractDAO（带有泛型 - 不会触发事件）：

public abstract class AbstractDAO<T extends Persistable> implements Serializable { @Inject @PostSaveEvent Event<T> postSaveEvent; public T saveOrUpdate(T object) throws DatabaseException { T obj = em.merge(object); postSaveEvent.fire(obj); } }

AbstractDAO（没有泛型，只是简单的类强制转换 - 触发事件）：

public abstract class AbstractDAO<T extends Persistable> implements Serializable { @Inject @PostSaveEvent Event<Polis> postSaveEvent; public T saveOrUpdate(T object) throws DatabaseException { T obj = em.merge(object); postSaveEvent.fire((Polis)obj); } }

PolisDAO类，它扩展了AbstractDAO并定义了泛型类型：

@Stateless @Named @PolisType public class PolisDAO extends AbstractDAO<Polis> { // some methods (saveOrUpdate is not overriden!) }

我的观察员班：

@Stateless @Named public class ProlongationService { public void attachProlongationToPolisOnSave(@Observes @PostSaveEvent Polis polis) throws DatabaseException { // ... DO smth with polis object. This is NOT called in the first case and called in the second }

这对我来说很奇怪，因为CDI事件的“ fire（） ”方法应该在运行时定义事件类型，而不是在编译或部署期间...当我调试时，我看到，

postSaveEvent.fire(obj);

从第一个样本开始与Polis实体完全一致。 但是没有发生任何事件......

UPD。 我尝试了基础泛型类，但没有运气：

@Inject @PostSaveEvent Event<Persistable> postSaveEvent;

谢谢。

I'm trying to send events and do this generically. I mean - create one abstract base DAO class with generic type and fire the event from its method. This should work for all descendants. This works if I define the exact type, but doesn't - if I use generics. What I mean:

AbstractDAO (with generics - doesn't fire the event):

public abstract class AbstractDAO<T extends Persistable> implements Serializable { @Inject @PostSaveEvent Event<T> postSaveEvent; public T saveOrUpdate(T object) throws DatabaseException { T obj = em.merge(object); postSaveEvent.fire(obj); } }

AbstractDAO (no generics, just simple class cast - fires the event):

public abstract class AbstractDAO<T extends Persistable> implements Serializable { @Inject @PostSaveEvent Event<Polis> postSaveEvent; public T saveOrUpdate(T object) throws DatabaseException { T obj = em.merge(object); postSaveEvent.fire((Polis)obj); } }

PolisDAO class, which extends AbstractDAO and defines the generic type:

@Stateless @Named @PolisType public class PolisDAO extends AbstractDAO<Polis> { // some methods (saveOrUpdate is not overriden!) }

My observer class:

@Stateless @Named public class ProlongationService { public void attachProlongationToPolisOnSave(@Observes @PostSaveEvent Polis polis) throws DatabaseException { // ... DO smth with polis object. This is NOT called in the first case and called in the second }

THis is very strange for me, as "fire()" method for CDI event should define the event type on runtime, not during compilation or deployment... When I debug, I see, that

postSaveEvent.fire(obj);

from the first sample operates exactly with Polis entity. But no event is fired nevertheless...

Upd. I tried the base generic class, but no luck:

@Inject @PostSaveEvent Event<Persistable> postSaveEvent;

Thanks.

最满意答案

从理论上讲，这应该可行，但实际上在运行时使用Java Reflection检查通用对象的类型有时是不可能的。 这是由于类型擦除。 IIRC具体子类的类型没有被删除，所以应该可以重新连接它，但我想现在实现不是这样做的。

将此文件作为http://issues.jboss.org/browse/WELD问题跟踪器中的错误（如果您使用的是Weld），以您提供的类为例，我们可以尝试修复它。

要解决此问题，请尝试将事件注入具体子类，并将其作为参数传递，或使用访问器方法将其传递到抽象超类中。

This should, in theory, work, however in practice inspecting the type of generic objects at runtime with Java Reflection is, at times, impossible. This is due to type erasure. IIRC the type of the concrete sub class isn't erased, so it should be possible to reconnect this, but I guess the implementation isn't doing this right now.

File this as a bug in the http://issues.jboss.org/browse/WELD issue tracker (if you are using Weld), with the classes you provide as an example and we can try to fix it.

To work around, try injecting the event into the concrete subclass, and passing it as an argument, or using an accessor method, to get it into the abstract super class.