java如何在动作合成中使用字段注入？

Question

Play 2.4支持开箱即用的依赖注入控制器。我已经成功地使用构造函数注入为我的控制器提供依赖项。但是，当使用action composition时，不会注入标有@Inject的字段

有没有办法将依赖项注入到复合操作中

控制器的示例代码：

public class Application extends Controller {
    private DomainService ds;

    @Inject
    public Application(DomainService ds) {
        this.ds = ds;
    }

    @Security.Authenticated(RandomAuthenticator.class)
    public Result index() {
        return ok();
    }

}

复合操作的示例代码：

public class RandomAuthenticator extends Security.Authenticator {
    @Inject private RandomService rs; // This field is never injected

    @Override
    public String getUsername(Context context) {
        float randFloat = rs.nextFloat(); // Error! rs is always null

        if (randFloat > 0.1) {
            return "foo";
        }

        return null;
    }
}

Answer 1

您可以尝试使用类的构造函数使用Guice进行注入，而不是字段注入：

public class RandomAuthenticator extends Security.Authenticator {

    private RandomService rs;   

    @Inject
    RandomAuthenticator(RandomService randomService) {
        this.rs = randomService;
    }

    @Override
    public String getUsername(Context context) {
        float randFloat = rs.nextFloat(); // Error! rs is always null

        if (randFloat > 0.1) {
            return "foo";
        }

        return null;
    }
}

Answer 2

public class RandomAuthenticator extends Security.Authenticator {

    private final RandomService rs;   

    public RandomAuthenticator(RandomService randomService) {
        this.rs = randomService;
    }

    ...
}

然后在Guice模块中使用@Providers方法：

@Provides
RandomAuthenticator provideRandomAuthenticator(RandomService randomService) {
    return new RandomAuthenticator(randomService);
}