Parsing nested JSON

Question

I have the following JSON:

{
  "registration": {
    "name": "Vik Kumar",
    "first_name": "Vik",
    "last_name": "Kumar",
    "bloodGroup": "B-",
    "gender": "male",
    "birthday": "10\/31\/1983",
    "email": "vik.ceo\u0040gmail.com",
    "cellPhone": "1234123456",
    "homePhone": "1234123457",
    "officePhone": "1234123458",
    "primaryAddress": "jdfjfgj",
    "area": "jfdjdfj",
    "location": {
      "name": "Redwood Shores, California",
      "id": 103107903062719
    },
    "subscribe": true,
    "eyePledge": false,
    "reference": "fgfgfgfg"
  }
}

I am using the following code to parse it:

JsonNode json = new ObjectMapper().readTree(jsonString);
JsonNode registration_fields = json.get("registration");

Iterator<String> fieldNames = registration_fields.getFieldNames();
while(fieldNames.hasNext()){
    String fieldName = fieldNames.next();
    String fieldValue = registration_fields.get(fieldName).asText();
    System.out.println(fieldName+" : "+fieldValue);
}

This works fine and it print all the values except for location which is kind of another level of nesting. I tried the same trick as above code to pass json.get("location") but that does not work. Please suggest how to make it work for location.

What do you mean by "does not work", do you get an error message? If so, what does it say? — Hunter McMillen, Sep 15 '12 at 01:04
Just to be clear the above code works fine. but when i try to apply the same logic for location field then the line location_fields.getFieldNames() throws null pointer exception. I am sure i am passing the right name "location" on the first line — Vik, Sep 15 '12 at 01:06

score 15 · Accepted Answer · answered Sep 15 '12 at 01:05

You need to detect when you are dealing with a (nested) Object using JsonNode#isObject:

public static void printAll(JsonNode node) {
     Iterator<String> fieldNames = node.getFieldNames();
     while(fieldNames.hasNext()){
         String fieldName = fieldNames.next();
         JsonNode fieldValue = node.get(fieldName);
         if (fieldValue.isObject()) {
            System.out.println(fieldName + " :");
            printAll(fieldValue);
         } else {
            String value = fieldValue.asText();
            System.out.println(fieldName + " : " + value);
         }
     }
}

Thus, when you reach an object, such as location, you'll call the printAll recursively to print all its inner values.

org.codehaus.jackson.JsonNode json = new ObjectMapper().readTree(jsonString);
org.codehaus.jackson.JsonNode registration_fields = json.get("registration");
printAll(registration_fields);

node.getFieldNames() is not available. Use node.fieldNames() instead? — Nagarajan Shanmuganathan, Sep 08 '16 at 11:03

score 1 · Answer 2 · answered Sep 15 '12 at 01:05

1

Since location is nested within registration, you need to use:

registration_fields.get("location");

to get it. But isn't it already processed by the while-loop, why do you need to get it separately?

answered Sep 15 '12 at 01:05

Barmar

741,623
53
500
612

2

He wants to print the contents of `location`. Since it's an object, its *text* value will be empty. – João Silva Sep 15 '12 at 01:07
well true but in that case how do i get those values? the current code line String fieldValue = registration_fields.get(fieldName).asText() prints blank – Vik Sep 15 '12 at 01:08

Parsing nested JSON

2 Answers2