Getting the values of a specific key from JsonNode

I have a JsonNode result represented as:

[
    {
        "item": {
            "type": "uri",
            "value": "http://www.wikidata.org/entity/Q42442324"
        },
        "prop": {
            "type": "uri",
            "value": "http://www.wikidata.org/prop/direct/P21"
        },
        "itemLabel": {
            "xml:lang": "en",
            "type": "literal",
            "value": "Kiisu Miisu"
        }
    },
    {
        "item": {
            "type": "uri",
            "value": "http://www.wikidata.org/entity/Q43260736"
        },
        "prop": {
            "type": "uri",
            "value": "http://www.wikidata.org/prop/direct/P21"
        },
        "itemLabel": {
            "xml:lang": "en",
            "type": "literal",
            "value": "Paddles"
        }
    }
]

I am trying to retieve the values of the key "value" into an array list using the below code but am getting the error Cannot invoke "com.fasterxml.jackson.databind.JsonNode.findValue(String)" because the return value of "com.fasterxml.jackson.databind.JsonNode.get(int)" is null

for (int i = 0; i < resultSize; i++) {
                JsonNode jsonObject = results.get(i);

                if (indexRow < jsonObject.size()) {
                    jsonRows = Collections.singletonList(jsonObject.get(indexRow++).findValue("value").asText());
                    
                }

            }

The value of variable jsonObject in the first iteration from the debugger is

{"item":{"type":"uri","value":"http://www.wikidata.org/entity/Q42442324"},"prop":{"type":"uri","value":"http://www.wikidata.org/prop/direct/P21"},"itemLabel":{"xml:lang":"en","type":"literal","value":"Kiisu Miisu"}}

Expected output is

["http://www.wikidata.org/entity/Q42442324", "http://www.wikidata.org/entity/Q42442324", "Kiisu Miisu", "http://www.wikidata.org/entity/Q43260736", "http://www.wikidata.org/prop/direct/P21", "Paddles"]

>Solution :

You can use elements() method and check if value key exist then add the value to list.

Smaple code

ObjectMapper mapper = new ObjectMapper();
JsonNode jsonNode = mapper.readTree(data);

List<String> values = new ArrayList<>();
jsonNode.forEach(jsonObject -> jsonObject.elements().forEachRemaining(valueNode -> {
    if(valueNode.has("value"))
        values.add(valueNode.get("value").asText());
}));
System.out.println(values);

Output:

[http://www.wikidata.org/entity/Q42442324, http://www.wikidata.org/prop/direct/P21, Kiisu Miisu, http://www.wikidata.org/entity/Q43260736, http://www.wikidata.org/prop/direct/P21, Paddles]