JSON: Parse ArrayNode of Arrays

Question

I'm trying to parse a JSON ArrayNode in Java but I'm having some issues.

The object is as follows:

{
  "type": "type",
  "id": "id",
  "attributes": {
    "x": [ "x.value" ],
    "y": [ "y.value" ],
    "z": [ "z.value" ]
  }
}

I'm parsing it as follows:

Map<String, Map<String, String>> users = new HashMap<>();
Iterator<JsonNode> arrayIterator = dataArray.elements();
while (arrayIterator.hasNext())
{
  JsonNode r = arrayIterator.next();
  String id = r.get("id").asText();
  users.put(id, new HashMap<>());
  Iterator<JsonNode> attributeIterator = r.path("attributes").elements();
  while (attributeIterator.hasNext())
  {
    JsonNode attribute = attributeIterator.next();
    users.get(id).put(attribute.asText(),
            attribute.elements().next().asText());
  }
}

But I'm getting a map like this:

"" => z.value

I found out in Java' documentation that the attribute .asText() will return empty if it is not a value node. How can I get that name so my map is instead:

x => x.value
y => y.value
z => z.value

What version of jackson are you using?

Gatusko
– Gatusko

2018-07-12 14:23:29 +00:00
Commented Jul 12, 2018 at 14:23 — Gatusko
– Gatusko, Commented Jul 12, 2018 at 14:23
Sorry, I'm using Jackson 2.6.5

javydreamercsw
– javydreamercsw

2018-07-12 16:13:33 +00:00
Commented Jul 12, 2018 at 16:13 — javydreamercsw
– javydreamercsw, Commented Jul 12, 2018 at 16:13

Gatusko · Accepted Answer · 2018-07-12 15:03:31Z

1

Well the first thing you need the keys of your JSON. So I tried with fields instead of only elements

  Iterator<Map.Entry<String, JsonNode>> attributeIterator = dataArray.path("attributes").fields();
            while (attributeIterator.hasNext())
            {
                Map.Entry<String, JsonNode> attribute = attributeIterator.next();
                users.get(id).put(attribute.getKey(),
                        attribute.getValue().get(0).asText());
            }

I didn't like to get an array So I change to this

Iterator<Map.Entry<String, JsonNode>> attributeIterator = dataArray.path("attributes").fields();
            while (attributeIterator.hasNext())
            {
                Map.Entry<String, JsonNode> attribute = attributeIterator.next();
                users.get(id).put(attribute.getKey(),
                        attribute.getValue().elements().next().textValue());
            }

The reason I used fields because I needed the key value :

Iterator that can be used to traverse all key/value pairs for object nodes; empty iterator (no contents) for other types

And elements doesn't include keys:

Method for accessing all value nodes of this Node, iff this node is a JSON Array or Object node. In case of Object node, field names (keys) are not included, only values. For other types of nodes, returns empty iterator.

From Java Docs

This is getting the map filled. I used jackson 2.9.4

edited Jul 12, 2018 at 15:03

answered Jul 12, 2018 at 14:49

Gatusko

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1 Comment

javydreamercsw Over a year ago

Had to change code to Iterator<Map.Entry<String, JsonNode>> attributeIterator = r.path("attributes").fields(); following my previous code to make it work but worked like a charm, thanks! Probably need to make that change for posterity.

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