java – 使用guice注入与actor抛出空指针

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.

解决方法

你得到了NullPointerException,因为Akka正在实例化你的猎犬演员,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,generate()必须在每次调用时创建一个新的Actor实例,它不能返回相同的实例.

然后你可以让Akka通过RetrieverDependencyInjector检索你的actor,例如：

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Actor作为构造函数参数的类来将RetrieverDependencyInjector变成GenericDependencyInjector,这可能允许你做类似的事情：

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

我没试过这个,但它可能会给你一个起点.