Json Question posted in
Our archive of expertly curated questions and answers provides insights and solutions to common problems related to this popular data interchange format. From parsing and manipulating JSON data to integrating it with various programming languages and web services, our archive has got you covered. Start exploring today and take your JSON skills to the next level

Java Jackson update json 2nd value instance in array

Hey all I am trying to figure out how to go about updating a part of my json. So far I have not found anywhere that shows me how to do this.

For an example, this is what I am needing to update:

{
    "lastUpdated": "",
    "firetvs": [
        {
            "name": "lr",
            "ip": "",
            "mac": "",
            "token": ""
        },
        {
            "name": "mbr",
            "ip": "",
            "mac": "",
            "token": ""
        },...ETC....

So I am needing to update the data under the

"name": "mbr"
 "mac": ""

part which I would need to update the mac address to something like:

"name": "mbr"
 "mac": "C1:41:Q4:E8:S1:98:V1"

I have found code that allows me to update a standard value like my lastUpdated but not for something that’s part of an array:

String jsonObject = "{" + 
    ""lastUpdated": ""," +
    ""firetvs": [" +
        "{" +
            ""name": "lr"," +
            ""ip": ""," +
            ""mac": ""," +
            ""token": """ +
        "}," +
        "{" +
            ""name": "mbr"," +
            ""ip": ""," +
            ""mac": ""," +
            ""token": """ +
        "}" +
    "]" +
"}";

ObjectMapper objectMapper = new ObjectMapper();
ObjectNode objectNode = null;

try {
    objectNode = objectMapper.readValue(jsonObject, ObjectNode.class);
    objectNode.put("lastUpdated", "02-08-2024");
    Log.d("test", objectNode.toPrettyString());
} catch (JsonProcessingException e) {
    throw new RuntimeException(e);
}

I did find this:

objectNode.with("firetvs").put("mac", "C1:41:Q4:E8:S1:98:V1");

But that wont work since its just going to find the first instance of "mac" and update that value instead of updating the 2nd instance of it. And I also get an error of:

Property ‘firetvs’ has value that is not of type ObjectNode (but com.fasterxml.jackson.databind.node.ArrayNode)

So, how would I accomplish this?

Tags:

2

Answers


  1. 0

    You may try JSON library Josson.

    https://github.com/octomix/josson

    Josson josson = Josson.fromJsonString(
    "{" +
        ""lastUpdated": ""," +
        ""firetvs": [" +
            "{" +
                ""name": "lr"," +
                ""ip": ""," +
                ""mac": ""," +
                ""token": """ +
            "}," +
            "{" +
                ""name": "mbr"," +
                ""ip": ""," +
                ""mac": ""," +
                ""token": """ +
            "}" +
        "]" +
    "}");
Map<String, JsonNode> params = Map.of(
    "$date", TextNode.valueOf("02-08-2024"),
    "$key", TextNode.valueOf("mbr"),
    "$val", TextNode.valueOf("C1:41:Q4:E8:S1:98:V1")
);
JsonNode node = josson.getNode("field(lastUpdated:$date, firetvs.field(mac:if([name=$key],$val,mac)))", params);
System.out.println(node.toPrettyString());

    Output

    {
  "lastUpdated" : "02-08-2024",
  "firetvs" : [ {
    "name" : "lr",
    "ip" : "",
    "mac" : "",
    "token" : ""
  }, {
    "name" : "mbr",
    "ip" : "",
    "mac" : "C1:41:Q4:E8:S1:98:V1",
    "token" : ""
  } ]
}
    Login or Signup to reply.
  2. 0

    Assuming that you know the indexes of the elements in firetvs to update, you could retrieve the firetvs property as an ArrayNode, instead of a JsonNode, and update the mac address only for the elements whose index matches the desired ones (in my demo I’ve added the desired indexes in a Set<Integer>).

    On a side note, the JsonNode.with() has been deprecated in favor of JsonNode.withObject().

    In this sample, I’ve added only a couple of elements within firetvs for demonstration’s sake. Here, at oneCompiler there’s a broader example.

    public class Main {
    public static void main(String[] args) throws JsonProcessingException {
        String json = "{n" +
                "    "lastUpdated": "",n" +
                "    "firetvs": [n" +
                "        {n" +
                "            "name": "lr",n" +
                "            "ip": "",n" +
                "            "mac": "",n" +
                "            "token": ""n" +
                "        },n" +
                "        {n" +
                "            "name": "mbr",n" +
                "            "ip": "",n" +
                "            "mac": "",n" +
                "            "token": ""n" +
                "        }n" +
                "    ]n" +
                "}";

        String mac = "C1:41:Q4:E8:S1:98:V1";
        Set<Integer> indexesToUpdate = new HashSet<>(Set.of(1, 3, 4));

        ObjectMapper objectMapper = new ObjectMapper();
        ObjectNode rootNode = objectMapper.readValue(json, ObjectNode.class);
        ArrayNode firetvsNode = (ArrayNode) rootNode.get("firetvs");
        indexesToUpdate.stream().forEach(i -> ((ObjectNode) firetvsNode.get(i)).put("mac", mac));

        String jsonMacReplaced = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(rootNode);
        System.out.println(jsonMacReplaced);
    }
}
    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search