Guice Inject in VertX

Question

I write on a VertX Application with multiple verticles, which access a database. Each database-package represents one java-class. Each of those classes can be implemented as a singleton class.

I made a little rep-case: 2 verticles, which are using the database.doLoginUser.

package testInject;

import io.vertx.core.DeploymentOptions;
import io.vertx.core.Vertx;


public class App {

    public static void main(String[] args) {
        Vertx vertx = Vertx.vertx();
        DeploymentOptions options = new DeploymentOptions().setWorker(true).setInstances(5);
        vertx.deployVerticle("java:testInject.Test1",options);
        vertx.deployVerticle("java:testInject.Test2",options);
    }
}

package testInject;

import com.google.inject.Inject;

public class Test1 extends MyVerticle {
 
    // @Inject
    Database     db = new Database();

    @Override
    public void start() throws Exception {
        System.out.println("Verticle " + this.getClass().getName() + " " + this);
        db.doLoginUser();
    }

}

package testInject;

import com.google.inject.Inject;

public class Test2 extends MyVerticle {
 
    // @Inject
    Database     db = new Database();

    @Override
    public void start() throws Exception {
        System.out.println("Verticle " + this.getClass().getName() + " " + this);
        db.doLoginUser();
    }

}

package testInject;

import io.vertx.core.Vertx;
import io.vertx.core.Context;
import io.vertx.core.AbstractVerticle;

abstract class MyVerticle extends AbstractVerticle {

    @Override
    public void init(Vertx vertx, Context context) {
        super.init(vertx,context);
        /* What to do to inject Database into the verticles ????*/
    }
}

package testInject;

import com.google.inject.Singleton;

@Singleton
public class Database {
    public void doLoginUser() {
        System.out.println("Done");
    }
}

To make things a bit easier, I don't want to implement every time the same pattern with Database db = Database.getInstance() or create in every verticle a new instance of this Database-Class (which is waste of memory). Just a "@Inject Database db" would be great.

Since VertX initialize the verticle-Classes over a Class-Name, I could not use the Guice-injector.getInstance(Test1.class) function, which is doing the binding. I didn't figure out, how to automatic bind the Database-Class within the constructor or an init-routine at time the verticle-class is created. Is my idea feasible and if yes how?

Thx Nik

Answer 1

I don't think you can inject into verticles the same way you would in Spring or Guice.

You should think of each verticle as of isolated java process, which you can only start or kill from the outside.

That means, you HAVE to create a db instance per verticle. Of course you can factor out its creation in your super-class MyVerticle to save some code, but db-per-verticle concept remains.

The vert.x-ish way of handling such problems would be to put the db instance inside another verticle, and communicate to it via Event-Bus.