How to execute Vertx Future in sequential order - vert.x

Question

In my sample project, I tried to do some initialization work when the application is started.
Java 16
Vertx 4.1.0
Check the complete project codes.
log.info("Data initialization is starting...");
var deleteComments = this.comments.deleteAll().onSuccess(event -> log.info("deleted comments: {}", event));
var deletePosts = this.posts.deleteAll().onSuccess(event -> log.info("deleted posts: {}", event));
var deleteUsers = this.authors.deleteAll().onSuccess(event -> log.info("deleted users: {}", event));
//log.info("deleted rows: authors: {}, comments: {}, posts: {}", authorsDel, commentsDel, postDel);
var insertData = this.authors.create("user", "user#example.com").onSuccess(
authorId -> {
IntStream.range(1, 5)
.forEach(
i -> {
this.posts.create("Dgs post #" + i, "test content of #" + i, PostStatus.DRAFT.name(), authorId).onSuccess(
postId -> {
IntStream.range(1, new Random().nextInt(5) + 1)
.forEach(c -> this.comments.create("comment #" + c, postId));
}
);
}
);
}
);
var printPosts = this.posts.findAll().onSuccess(p -> log.info("post: {}", p));
var printComments = this.comments.findAll().onSuccess(p -> log.info("comment: {}", p));
var printAuthors = this.authors.findAll().onSuccess(p -> log.info("author: {}", p));
deleteComments
.flatMap(integer -> deletePosts)
.flatMap(integer -> deleteUsers)
.flatMap(integer -> insertData)
.flatMap( uuid -> printPosts)
.flatMap(postEntities -> printComments)
.flatMap(commentEntities -> printAuthors)
.onSuccess(event -> log.info("done"));
log.info("done data initialization...");
But it does not work as expected.
There is no a then method like Reactor.
And the Future.result() will return an exception instead of a blocking call(how to make execution in a blocking way, I thought it is a blocking invocation).
I can not find an effective way to execute them in sequential order.
Update:
I changed the codes as suggested.
this.comments.deleteAll().onSuccess(event -> log.info("deleted comments: {}", event))
.flatMap(r -> this.posts.deleteAll().onSuccess(event -> log.info("deleted posts: {}", event)))
.flatMap(r -> this.authors.deleteAll().onSuccess(event -> log.info("deleted users: {}", event)))
.flatMap(r -> this.authors.create("user", "user#example.com")
.onSuccess(
authorId -> {
log.info("inserted user: {}", authorId);
IntStream.range(1, 5)
.forEach(
i -> {
this.posts.create("Dgs post #" + i, "test content of #" + i, PostStatus.DRAFT.name(), authorId).onSuccess(
postId -> {
log.info("inserted post: {}", postId);
IntStream.range(1, new Random().nextInt(5) + 1)
.forEach(c -> this.comments.create("comment #" + c, postId)
.onSuccess(id -> log.info("inserted comment: {}", id))
);
}
);
}
);
}
)
)
.flatMap(r -> this.posts.findAll().onSuccess(p -> log.info("saved posts: {}", p)))
.flatMap(r -> this.comments.findAll().onSuccess(p -> log.info("saved comments: {}", p)))
.flatMap(r -> this.authors.findAll().onSuccess(p -> log.info("saved authors: {}", p)))
.onSuccess(event -> log.info("done data initialization..."));
And got the following log in the console.
10:20:46.699 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - Data initialization is starting...
10:20:47.768 [vert.x-eventloop-thread-1] INFO com.example.demo.MainVerticle - HTTP server started on port 8080
10:20:47.768 [vert.x-eventloop-thread-0] INFO i.v.c.i.l.c.VertxIsolatedDeployer - Succeeded in deploying verticle
10:20:47.918 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - deleted comments: 10
10:20:47.942 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - deleted posts: 4
10:20:47.960 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - deleted users: 1
10:20:48.022 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted user: 260fee93-cf60-408d-a3e9-f7b08ed7545a
10:20:48.047 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - saved posts: []
10:20:48.052 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted post: 57a936e2-9611-43b5-94e2-1b01069cd327
10:20:48.056 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - saved comments: []
10:20:48.067 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - saved authors: [AuthorEntity[id=260fee93-cf60-408d-a3e9-f7b08ed7545a, name=user, email=user#example.co
m, createdAt=null]]
10:20:48.092 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - done data initialization...
10:20:48.112 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted post: 534b99ae-4847-4cea-84c1-88cea87f20b7
10:20:48.117 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted post: f7dca2eb-0954-4368-b9b6-68a00f6748f2
10:20:48.120 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted post: 02e8f84f-25dd-4d69-b7f1-8c125ce35bc1
10:20:48.131 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted comment: b9bf618a-f579-48f5-96cc-51f962ca041c
10:20:48.134 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted comment: 052cfde8-627d-4cb3-8812-5543673a20ea
10:20:48.143 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted comment: 69a5dc2b-30f8-4008-90a1-e8c724336dcd
10:20:48.149 [vert.x-eventloop-thread-1] INFO com.example.demo.DataInitializer - inserted comment: a19c2626-1546-4ba0-a663-823df08d836f
How to make sure all futures in the insert block are completed before entering the print result.

Answer 1

It's most likely because your deleteAll and findAll operations are not lazy. Because of this, they are running as soon as you call them. Instead of doing:
deleteComments
.flatMap(integer -> deletePosts)
...
You want to be doing this:
deleteComments
.flatMap(integer -> this.posts.deleteAll())
...
This will make sure that they will run sequentially. If you want something that's more similar to Reactor, you can take a look at the RxJava3 extensions or mutiny bindings for Vert.x.