I'm new in VertX framework (and reactive programming too). when I read about 'Future', I don't understand what is the usage of the 'completer' method, and when do must be used from that? I will appreciate if someone could help me?
Vert.x asynchronous methods are often defined using a Handler<AsyncResult<X>> parameter. This parameter is the callback invoked when the operation completes.
vertx.createHttpServer().listen(ar -> {
// callback implementation
});
As you noticed, in the latest versions of Vert.x, a Future<X> implements Handler<AsyncResult<X>> so you can create a future and use it directly as an asynchronous operation parameter:
Future<HttpServer> serverFuture = Future.future();
vertx.createHttpServer().listen(future);
And then you can use the future methods like map or compose.
In older versions, a future wasn't a handler for asynchronous results, so you had to use the completer method:
Future<HttpServer> serverFuture = Future.future();
vertx.createHttpServer().listen(future.completer());
As of 3.7.0, the completer method is deprecated and will be removed in version 4.