How does RequestScope in Quarkus/CDI work?

Question

I did some experimentation with Quarkus and I am having difficulties understanding how @RequestScoped works. Coming from Spring, I would be expecting that the following code should not work and throw an Exception:

@ApplicationScoped
public class AppLifecycleBean {

    @Inject
    MyBean myBean;

    void onStart(@Observes StartupEvent ev) {
        myBean.doSomething();
    }
}

@RequestScoped
public class MyBean {
    public void doSomething() {
        System.out.println("Hello!");
    }
}

The request scoped bean is correctly injected as a proxy. But calling a method on the proxy even when there is no request available seems to work just fine?

It works just like you expect, the only thing you need to realize is that there's more notions of "request" than just HTTP request. In other words, the request context is activated on more occasions than just for processing an HTTP request. Quarkus specifically documents that the request context is activated for notifications of synchronous observers, which is the behavior you see: quarkus.io/guides/cdi-reference#request-context-lifecycle — Ladicek
– Ladicek, Commented Jul 1, 2022 at 17:23
Ok, that makes sense. Just out of curiosity: is there some overview where all those other types of requests that work with @RequestScoped are documented? I did not explicitely find something in the Quarkus documentation (except the one you already mentioned). I also discovered myself that @Scheduled method also seems to work with @RequestScoped. — Dave
– Dave, Commented Jul 12, 2022 at 18:36
I don't think there's a list, no. But in general, I think most Quarkus extensions activate the request context whenever they start a new independent "thread" of execution, because that is conceptually a request. Plus it's convenient to be able to use @RequestScoped beans [almost] anywhere. (Putting the word "thread" into quotes, because I'm not talking about java.lang.Thread, hope you see what I mean by that.) — Ladicek
– Ladicek, Commented Jul 13, 2022 at 7:20
@Ladicek just for clarification - is the example code provided by the OP a bug? Or is injecting RequestScoped bean into ApplicationScoped class acceptable in Quarkus? — nogridbag
– nogridbag, Commented Dec 16, 2023 at 20:01
Injecting a bean with a narrow scope into a bean with a wider scope is very much valid, yes. For all normal scopes (including @ApplicationScoped and @RequestScoped), the thing that is injected is a client proxy, which obtains the correct "current" instance on each method call. — Ladicek
– Ladicek, Commented Dec 17, 2023 at 17:48

Adrian Mole · Accepted Answer · 2023-04-30 11:53:51Z

1

If a bean class has the annotation @RequestScoped, CDI will lazily instantiate the bean during the first call to a bean method. Such a bean lives only within a chain used to process a single HTTP request.

Overview of Bean Scopes in Quarkus

edited Apr 30, 2023 at 11:53

Adrian Mole

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answered Apr 25, 2023 at 8:15

Garvit Khandelwal

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