使用guice注入与actor抛出空指针

Question

我在服务器的字段注入上获得空指针异常,该服务器作为akka actor启动.

计划部分:

private ActorRef myActor = Akka.system().actorOf(
        new Props(Retreiver.class));

@Override
public void onStart(Application app) {
    log.info("Starting schedular.....!");
    Akka.system()
            .scheduler()
            .schedule(Duration.create(0, TimeUnit.MILLISECONDS),
                    Duration.create(30, TimeUnit.MINUTES), myActor, "tick",
                    Akka.system().dispatcher());

}

Retreiver类部分:

public class Retreiver extends UntypedActor {

private Logger.ALogger log = Logger.of(Retreiver .class);

@Inject
private myDataService dataService;

@Override
public void onReceive(Object arg0) throws Exception {

    if (0 != dataService.getDataCount()) {
    ....
    ....
    ....
    }

}

我为dataService获取null.请就此向我提出建议.

谢谢.

Answer 1

对于任何需要这个的人:

public class GuiceInjectedActor implements IndirectActorProducer {

final Injector injector;
final Class<? extends Actor> actorClass;

public GuiceInjectedActor(Injector injector, Class<? extends Actor> actorClass) {
    this.injector = injector;
    this.actorClass = actorClass;
}

@Override
public Class<? extends Actor> actorClass() {
    return actorClass;
}

@Override
public Actor produce() {
    return injector.getInstance(actorClass);
}

}

和

Akka.system().actorOf(Props.create(GuiceInjectedActor.class, INJECTOR,Retreiver.class))

而已...!!!

Answer 2

你得到的是NullPointerException因为Akka正在实例化你的Retriever演员,而不是Guice.您需要让Guice构建您的实例,然后将其传递给Akka,IndirectActorProducer可以帮助您实现此目的,例如:

class RetrieverDependencyInjector implements IndirectActorProducer {
    final Injector injector;

    public RetrieverDependencyInjector(Injector injector) {
        this.injector = injector;
    }

    @Override
    public Class<? extends Actor> actorClass() {
        return Retriever.class;
    }

    @Override
    public Retriever produce() {
        return injector.getInstance(Retriever.class);
    }
}

请注意,每次调用时都produce() 必须创建一个新Actor实例,它不能返回相同的实例.

然后,您可以通过以下方式让Akka检索您的演员RetrieverDependencyInjector:

ActorRef myActor = Akka.system().actorOf(
    Props.create(RetrieverDependencyInjector.class, injector)
);

UPDATE

我想你进一步评论,你可以通过提供你想要的类作为构造函数参数来RetrieverDependencyInjector变成一个,这可能会允许你做类似的事情:GenericDependencyInjectorActor

Props.create(GenericDependencyInjector.class, injector, Retriever.class)

我没试过这个,但它可能会给你一个起点.