How can I implement custom asynchronous operation in Vert.x?

Question

I am newbie in Vert.x.

For example, JDBCClient has non-blocking method

JDBCClient.getConnection(Handler<AsyncResult<SQLConnection>> handler)

When I call it, it is really asynchronous.

jdbcClient.getConnection(result -> { /* this code will execute asynchonous */})

But how can I implement my own component with non-blocking methods?

When I write for example this, it doesnt looks asynchronous. It just will execute method body and then will call passed lambda.

 class MyComponent { 
   public void getSomething(Handler<AsyncResult<String>> handler) {
       String result = someHeavyMethodInThisThread();
       handler.handle(Future.succeededFuture(result));
   }
 }
 /* later */

 /* this code will be blocking, right? */
 myComponent.getSomething(res -> { /* ... */ })

Maybe there is way to tell Vert.x that my method should be asynchronous? Some annotation or something else?

Answer 1

There is nothing wrong with your code, your code style, normally will be async because the moment you perform a IO operation or call a vert.x API a async operation will detach you from the current thread (event loop).

In your case you're doing CPU bound code so it does not behave as async and as you stated will just call the lambda. If you want nevertheless make it async you can always wrap your code with runOnContext and that will enqueue it to be run on the next iteration of the event loop, e.g.:

class MyComponent { 
  public void getSomething(Handler<AsyncResult<String>> handler) {
    vertx.runOnContext(v -> {
      String result = someHeavyMethodInThisThread();
      handler.handle(Future.succeededFuture(result));
    });
  }
}