Weld中的JavaEE CDI:通用事件？

Question

我有一个基于泛型的特定事件处理的想法,但似乎Weld无法处理它们.我问谷歌但是找不到替代的CDI扩展.

问题:是否有CDI扩展,可以处理泛型类型事件的事件传播？

在下面我有明确的问题.

我有三个常规事件,EntityCreated,EntityChanged和EntityDeleted.它们的基类定义如下:

public abstract class DatabaseEvent<TargetType> {

    public TargetType target;

    public DatabaseEvent(TargetType target) {
        this.target = target;
    }
}

然后事件是简单的继承类:

public class EntityCreatedEvent<TargetType> extends DatabaseEvent<TargetType> {

    public EntityCreatedEvent(TargetType target) {
        super(target);
    }
}

我像这样解雇他们:

public abstract class MyHome<EntityType> {

    private EntityType entity;

    @Inject
    Event<EntityCreatedEvent<EntityType>> entityCreatedEvent;

    public void fireCreatedEvent() {
        EntityCreatedEvent<EntityType> payload = new EntityCreatedEvent<EntityType>(entity);
        entityCreatedEvent.fire(payload);
    }
}

我想像这样观察它们:

public void handleProjectCreated(@Observes EntityCreatedEvent<Project> event) { ... }

启动服务器时,Weld告诉我它无法处理泛型类型的事件.CDI的做法是使用额外的限定符而不是泛型来消除它们,例如:

public void handleProjectCreated(@Observes @ProjectEvent EntityCreatedEvent event) { ... }

但是,我从该MyHome基类中触发事件,在那里我不能只用以下内容触发@ProjectEvent:它可能不是项目而是另一种类型.

到目前为止,我的解决方案是完全跳过键入并按照以下方式处理它们:

public void handleProjectCreated(@Observes EntityCreatedEvent event) { 
    if(event.target instanceof Project) { ... }
}

这个解决方案没问题,但并不完美.

Answer 1

我想你可以用dinamically绑定限定符成员来做到这一点.这就是您的代码的样子:

public abstract class MyHome {

    private EntityType entity;

    @Inject
    Event<EntityCreatedEvent> entityCreatedEvent;

    public void fireCreatedEvent() {
        entityCreatedEvent.select(getTypeBinding()).fire(new EntityCreatedEvent(entity));
    }

    private TypeBinding getTypeBinding() {
        return new TypeBinding() {
        public Class<? extends EntityType> value() {return entity.getClass();}
    };
}

@Qualifier
@Target({ PARAMETER, FIELD })
@Retention(RUNTIME)
public @interface EntityTypeQualifier {
    Class<? extends EntityType> value();
}

public abstract class TypeBinding extends AnnotationLiteral<EntityTypeQualifier> implements EntityTypeQualifier {}

//Observers
public void handleEntityType1Created(@Observes @EntityTypeQualifier(EntityType1.class) EntityCreatedEvent event) {}
public void handleEntityType2Created(@Observes @EntityTypeQualifier(EntityType2.class) EntityCreatedEvent event) {}