[FIXED] Vert.x - Not able to decode json to list of objects

Issue

I'm using the latest version of Vert.x (4.3.2) and I wrote and handler for a route that serves a POST method.

Below my code to convert the JSON body of that method to a List of objects:

Class<List<CartLineItem>> cls = (Class<List<CartLineItem>>)(Object)List.class;
List<CartLineItem> itemsToAdd = rc.body().asPojo(cls);

Unforntunately whenever I try to iterate over itemsToAdd I get the exception: java.lang.ClassCastException: class java.util.LinkedHashMap cannot be cast to class com.acme.CartLineItem.

How can I fix this issue without using any other library except Vert.x (I mean .. using Jackson I would provide a TypeReference<List> object)?

Solution

In Vert.x 3 there was method that you could use:

Json.decodeValue(result.bodyAsString(), new TypeReference<List<ConditionDTO>>() {});

Since in Vert.x 4 this was removed you will need to use specific class DatabindCodec: io.vertx.core.json.jackson.DatabindCodec.fromString(result.bodyAsString(), new TypeReference<List<SimpleDTO>>() {})

If you don't want to use external libraries there is an option to iterate over an jsonArray that you have in body assuming body is something like this:

[{"name":"Lazar", "age":27},{"name":"Nikola", "age":33}]

List<SimpleDTO> list = routingContext.body().asJsonArray()
    .stream()
    .map(json -> Json.decodeValue(json.toString(), SimpleDTO.class))
    .collect(Collectors.toList());

Answered By - Pendula
Answer Checked By - Marie Seifert (JavaFixing Admin)