Vertx and Dependency Injection (Guice) Scopes

[Jens K]

Hi,

I'm working on a vertx app using the vertx-guice library listed in vertx-awesome. In my application I have a couple of objects that can be safely shared across several verticles. I marked them as Singleton, but it seems to be that they are initialized two times when I launch vertx with DeploymentOptions.setInstances(2). When I run the example from below, the output is something like

look another instance sandbox.ThreadSafeSingleton@c2c7e5b

look another instance sandbox.ThreadSafeSingleton@74271cea

Is there a way to share objects between verticles using guice DI?

public class Sandbox {
    public static void main(String[] args){
        CompletableFuture<Void> future = new CompletableFuture<>();
        JsonObject config = new JsonObject().put("guice_binder", SimpleModule.class.getName());
        Vertx.vertx().deployVerticle("java-guice:" + SimpleVericle.class.getName(), new DeploymentOptions().setConfig(config).setInstances(2), result -> {
            if (result.succeeded()) {
                future.complete(null);
            } else {
                result.cause().printStackTrace();
                future.completeExceptionally(result.cause());
            }
        });
    }
}


public class SimpleModule extends AbstractModule{


    @Override
    protected void configure() {
        bind(ThreadSafeSingleton.class).asEagerSingleton();
    }
}


public class SimpleVericle extends AbstractVerticle {


    @Inject ThreadSafeSingleton threadSafeSingleton;




    @Override
    public void start() throws Exception {
        System.out.println("look another instance "+threadSafeSingleton.toString());
    }
}


public class ThreadSafeSingleton {
}

[Clement Escoffier]

Hi,

Did you have a look to https://github.com/englishtown/vertx-guice ? 

Clement

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[Jens K]

Yes, that is the extension that I'm using and what I meant with "I'm working on a vertx app using the vertx-guice library listed in vertx-awesome.".

[Tim Fox]

I doubt this is due to Vert.x doing anything strange as Vert.x uses a flat classloader model in the below example.

What happens if you just create two instances of your SimpleVerticle class directly?

[Jens K]

I'm not sure if I understand you correctly: you mean writing something like this

new SimpleVerticle().start();
new SimpleVerticle().start();

? I guess a NPE will be thrown due to a non-initialized ThreadSafeSingleton-instance.

[Jens K]

I think the problem is, that the GuiceVerticleLoader from vertx-guice is creating an injector for each deployed verticle and therefore a singleton is scoped to a verticle. 

[jklingsporn]

I created a Pull-Request: https://github.com/englishtown/vertx-guice/pull/7

[Swetha Ramaiah]

Hello

I am using this vertx-guice library and I have a constructor in my class which extends AbstractModule. How do I go about adding values to constructor in JsonConfig while invoking this DBModule class using guice_binder

class DBModule extends AbstractModule {
  DBModule(Config config) {
    // do something
  }
@Override
    protected void configure() {
        //
    }
}

[Thomas SEGISMONT]

Hi

I'll let someone from the community reply if they are familiar with the vertx-guice library.

But it isn't part of the vertx-stack so if you don't get an answer here you can try to post an issue the vertx-guice repo on GitHub

Regards

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[Sirozha]

Hello Thomas SEGISMONT

I'm wondering what lib is a part of vertx-stack considering DI?

[Thomas SEGISMONT]

Vert.x does not mandate usage of DI.

There are so community integrations (eg vertx-guice) or we have working examples in the vertx-examples with Spring.

If you're looking for annotation driven, opinionated framework for reactive development with Vert.x, I would recommend to give Quarkus a try.

Le mer. 19 févr. 2020 à 11:33, Sirozha <siro...@gmail.com> a écrit :

Hello Thomas SEGISMONT

I'm wondering what lib is a part of vertx-stack considering DI?

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[Dan O'Reilly]

I believe you can use Vertx.currentContext().config() inside your Module to get access to the config you passed to the Verticle. I'm not 100% sure if this is what you're asking, though...If it's not, can you clarify what you're trying to do?

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[Swetha Ramaiah]

Hi 

I found this other implementation that works for my use case

But I was referring to this example here that uses vertx-guice library

https://github.com/ltamrazov/vertx-starter-guide/blob/part-3/src/main/java/com/ltamrazov/vertxstarterguide/ServiceBinder.java

ServiceBinder extends AbstractModule. In my case, I have a constructor for my ServiceBinder(AppConfig appConfig) class.

So when I use the following snippet, I get an error message saying ServiceBinder class could not be instantiated as it expects a constructor.

private static Future<Void> deploy(Vertx vertx, Class verticle, DeploymentOptions opts){
        Future<Void> done = Future.future();
        String deploymentName = "java-guice:" + verticle.getName();
        JsonObject config = new JsonObject()
                .put("guice_binder", ServiceBinder.class.getName());

        opts.setConfig(config);

        vertx.deployVerticle(deploymentName, opts, r -> {
            if(r.succeeded()){
                System.out.println("Successfully deployed verticle: " + deploymentName);
                done.complete();
            }
            else {
                System.out.println("Failed to deploy verticle: " + deploymentName);
                done.fail(r.cause());
            }
        });

        return done;
    }

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Regards,
Swetha