java - 谷歌Guice : use injected factory to instantiate multiple objects in a class?

Question

public class AppModule extends AbstractModule {
    @Override
    protected void configure() {
        install(new FactoryModuleBuilder().implement(BaseClass.class, ImplementingClass.class).build(FactoryClass.class));
    }
}

public class AnotherClass {
    @Inject
    private FactoryClass factoryClass;

    private BaseClass firstBaseObject = factoryClass.create("some_parameter");
    private BaseClass secondBaseObject = factoryClass.create("another_parameter");

    public void processSomething() {
        // ... do something that requires both firstBaseObject and secondBaseObject to already be initialized on each call
    }
}

有没有办法让我在每次调用 processSomething() 时都可以访问 firstBaseObject 和 secondBaseObject ？ processSomething() 的每次调用都依赖于已经实例化的这两个对象，并且它们是具有大量元数据的巨大对象。即，我可以以某种方式确保在命中这两行时 factoryClass 已经实例化吗？:

    private BaseClass firstBaseObject = factoryClass.create("some_parameter");
    private BaseClass secondBaseObject = factoryClass.create("another_parameter");

我在这两行上收到 NullPointerExceptions，因为 factoryClass 为 null。

如果您需要更多信息，请告诉我，非常感谢!

Answer 1

使用下面的代码

public class AnotherClass {
    private final BaseClass firstBaseObject;
    private final BaseClass secondBaseObject;

    @Inject
    public AnotherClass(FactoryClass factoryClass) {
       firstBaseObject = factoryClass.create("some_parameter");
       secondBaseObject = factoryClass.create("another_parameter");
    }

    public void processSomething() {
        // ... do something that requires both firstBaseObject and secondBaseObject to already be initialized on each call
    }
}

不能使用字段或方法注入(inject)，因为factoryClass中的注入(inject)是在填充firstBaseObject和secondBaseObject之后进行的。

或者

public class AppModule extends AbstractModule {
    @Override
    protected void configure() {
        ...
        bind(BaseClass.class)
        .annotatedWith(Names.named("firstBaseObject"))
        .toInstance(factoryClass.create("some_parameter"));

        bind(BaseClass.class)
        .annotatedWith(Names.named("secondBaseObject"))
        .toInstance(factoryClass.create("another_parameter"));
    }
}

public class AnotherClass {
    @Inject
    @Named("firstBaseObject")
    private BaseClass firstBaseObject;
    @Inject
    @Named("secondBaseObject")
    private BaseClass secondBaseObject;

    public void processSomething() {
        // ... do something that requires both firstBaseObject and secondBaseObject to already be initialized on each call
    }
}