JsonArray element class inconsistency

[Thomas Gilbert]

Hi All,

I'm a vertx beginner, so apologizes if I misunderstood something.

I noticed the following, if I send a JSONArray of JsonObjects through the event bus, the consumer receives a list of:

- JSONObject if the consumer if running locally, in the same JVM (which is nice)

- LinkedHashMap objects if the consumer is running in a other node of the vertx cluster

I find this very inconvenient because I cannot assume that my consumer always receives JSONObjects (or maps) and have lots of type safety checks to add in order to avoid exceptions. 

I would have expected that either:

- JsonObject implements Map so that whatever I receive I can cast it to a map

- all my consumers receive JsonObjects (and their convenient methods) whereever they run

Thanks for your feedback,

Thomas

[Julien Viet]

normally they should receive json object

can you show us some code or give a reproducer ?

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[Thomas Gilbert]

Thank you for your answer. Here is a code sample. The goal is to create a simple vertx cluster and send objects including a jsonarray.

import io.vertx.core.Vertx;
import io.vertx.core.VertxOptions;
import io.vertx.core.eventbus.Message;
import io.vertx.core.json.JsonArray;
import io.vertx.core.json.JsonObject;
import io.vertx.spi.cluster.hazelcast.HazelcastClusterManager;

public class Main {

    public static void main(String[] args) {
        Vertx.clusteredVertx(new VertxOptions().setClusterManager(new HazelcastClusterManager()), res -> {
            if (res.succeeded()) {
                Vertx vertx = res.result();

                vertx.eventBus().consumer("example", Main::handleExample);

                JsonObject  request = new JsonObject()
                                        .put("foo", "bar")
                                        .put("array", new JsonArray()
                                                .add(new JsonObject().put("foo", "bar"))
                                                .add(new JsonObject().put("foo", "bar"))
                                        );

                vertx.setPeriodic(1000, id -> {
                    vertx.eventBus().send("example", request, response -> {
                        JsonObject jsonResponse = (JsonObject) response.result().body();
                        System.out.println(jsonResponse.getJsonArray("array").getList().get(0).getClass() + " received in the response");
                    });
                });

            } else {
                // failed!
            }
        });
    }

    private static void handleExample(Message<JsonObject> message) {
        JsonObject  response = new JsonObject()
                .put("baz", "qux")
                .put("array", new JsonArray()
                        .add(new JsonObject().put("baz", "quz"))
                        .add(new JsonObject().put("baz", "quz"))
                );

        JsonArray   requestArray = message.body().getJsonArray("array");
        System.out.println(requestArray.getList().get(0).getClass() + " received in the request");

        message.reply(response);
    }

}

If you look at the output, it's saying:

class io.vertx.core.json.JsonObject received in the request
class io.vertx.core.json.JsonObject received in the response
class io.vertx.core.json.JsonObject received in the request
class io.vertx.core.json.JsonObject received in the response
class io.vertx.core.json.JsonObject received in the request
class io.vertx.core.json.JsonObject received in the response

if I start only one instance of this program. As soon as I start multiple onces (and Vertx starts distributing the messages), I've got things like this:

class java.util.LinkedHashMap received in the request
class java.util.LinkedHashMap received in the response
class io.vertx.core.json.JsonObject received in the request
class io.vertx.core.json.JsonObject received in the response
class java.util.LinkedHashMap received in the request
class java.util.LinkedHashMap received in the response
class io.vertx.core.json.JsonObject received in the request
class io.vertx.core.json.JsonObject received in the response
class java.util.LinkedHashMap received in the request
class java.util.LinkedHashMap received in the response

[Julien Viet]

ah,

you should not use the getList() or getMap() methods as they return the raw data (the doc says “Get the underlying list”).

instead you should do jsonResponse.getJsonArray(array).getValue(0)

Julien

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[Thomas Gilbert]

I see. Thanks!

This can indeed help if I wanna get one element at a time.

On the other hand, I cannot do things such as:

- array.getList().sort() to sort the results after I receive them

- array.sublist() to make chunks of requests received by my web handler

etc... 

Again, too bad that JsonObject does not implement Map, it would have make things a lot easier in my opinion.

[Julien Viet]

if you iterate the list first, it will change all LinkedHashMap value to JsonArray and then you can use the underlying list

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